Water treatment controller

Abstract

A water treatment controller, for example a swimming pool controller, comprises a cartridge 230 and a controller unit 225. The cartridge comprises a pump to dose a treatment fluid, such as an acid and

Description

FIELD OF THE INVENTION The present invention relates to water treatment control systems, and in particular to a bathing water treatment controller, such as a swimming pool or hot tub controller. BACKGROUND Water treatment facilities are important for monitoring, maintaining and improving the quality of water, so as to improve the water’s cleanliness and make it safe for use. For example, the quality of water is normally monitored and maintained in applications like drinking, irrigation, water recreation and bathing and so on. Water treatment control systems are used in such facilities to monitor and maintain the water quality. A swimming pool controller is an example of a controller for a water treatment control system. The same or similar controllers are used in other bathing facilities like hot tubs, whirlpools and spa pools, as well as in natural bathing ponds. Such controllers measure water properties and take remedial action when the water properties are found to deviate from safe or user-preferred levels. Monitored water properties include chemical dosing levels, cleanliness, water circulation and temperature. Conventional swimming pool control systems include multiple, separately housed components, e.g., a main control box close to the pool and separately located components such as a water sensing probe, water pump and water filters. These separately components need to be individually serviced and replaced over time as they begin to fail. This can be costly and inconvenient to pool owners, as each component needs to be serviced and replaced when it wears down / fails. Such components can also be prone to leakages and inaccurate readings. As such, there is a need for improved water treatment control systems that overcome the above issues. SUMMARY In a first aspect, there is provided a water treatment controller comprising a cartridge and a controller unit. The water treatment controller is for monitoring, maintaining and improving water quality, for example bathing water in a swimming pool, hot tub, whirlpool, spa pool, natural bathing pond etc. The water treatment controller may be part of a water treatment control system, such as a swimming pool control system. The cartridge of the water treatment controller comprises a cartridge treatment fluid inlet and a cartridge treatment fluid outlet connected by a cartridge treatment fluid flow path, and a treatment fluid pump mechanism located on the cartridge treatment fluid flow path. The treatment fluid pump mechanism is operable to pump a treatment fluid along the cartridge treatment fluid flow path from the cartridge treatment fluid inlet to the cartridge treatment fluid outlet. The treatment fluid is a fluid for treating the water, and may be an acid (such as hypochlorous acid) or a disinfectant (such as chlorine or a chlorine-producing chemical like bleach) for example. The treatment fluid may instead be referred to as a dosing fluid. The cartridge also comprises a cartridge water inlet and a cartridge water outlet connected by a cartridge water flow path, a water test chamber located on the cartridge water flow path such that water flowing along the cartridge water flow path flows into and out of the water test chamber, and a test probe configured to measure a property of water in the water test chamber and to provide a measurement signal indicative of the measured property to a controller of the controller unit. Exemplary measured water properties include the pH of the water, the oxygen reduction potential of the water, and the temperature of the water. The measurement signal may be an electrical signal or an optical signal indicative of the measured water property. The cartridge also has a cartridge fastener fitting for fastening the cartridge to the controller unit. The controller unit of the water treatment controller comprises a controller upstream water inlet and a controller upstream water outlet connected by a controller upstream water flow path, and a controller downstream water inlet and a controller downstream water outlet connected by a controller downstream water flow path. The controller unit also comprises a controller unit fastener fitting, and the cartridge fastener fitting and the controller unit fastener fitting co-operate to allow the cartridge to be fastened to and unfastened from the controller unit. The treatment fluid pump mechanism comprises a pump motor located in the controller unit or in the cartridge. When the cartridge is fastened to the controller unit, the controller upstream water outlet makes fluid connection with the cartridge water inlet, and the cartridge water outlet makes fluid connection with the controller downstream water inlet, such that water can flow along the controller upstream water flow path, the cartridge water flow path and the controller downstream water flow path. Also, the test probe and the controller are communicatively coupled so that the measurement signal provided by the test probe is received by the controller, and the controller and the pump motor are communicatively coupled so that a pump control signal outputted by the controller is received by the pump motor. Furthermore, the controller is configured to produce the pump controller signal to control the pump motor in response to the received measurement signal, the pump control signal causing the pump motor to drive the treatment fluid pump mechanism to pump the treatment fluid along the cartridge treatment fluid flow path. Accordingly, when connected to a treatment fluid supply, the water treatment controller can dose the water with treatment fluid, e.g., acid may be pumped from an acid tank into bathing water thereby decreasing the pH of the water. The controller unit of the water treatment controller may further comprise a controller upstream treatment fluid inlet and a controller upstream treatment fluid outlet connected by a controller upstream treatment fluid flow path, and a controller downstream treatment inlet and a controller downstream treatment fluid outlet connected by a controller downstream treatment fluid flow path. As such, when the cartridge is fastened to the controller unit, the controller upstream treatment fluid outlet makes fluid connection with the cartridge treatment fluid inlet, and the cartridge treatment fluid outlet makes fluid connection with the controller downstream treatment fluid inlet, such that the treatment fluid can flow along the controller upstream treatment fluid flow path, the cartridge treatment fluid flow path and the controller downstream treatment fluid flow path. One or more of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet may each comprise a self-sealing valve configured to i) seal the valve, thereby stopping fluid flow into, and out of, the respective water flow paths and treatment fluid flow paths when the cartridge fastener fitting is not fastened to the controller unit fastener fitting, and ii) open the valve, thereby allowing fluid flow into, and out of, the respective water flow paths and treatment fluid flow paths when the cartridge fastener fitting is fastened to the controller unit fastener fitting. Advantageously, the self-sealing valves stop water and / or treatment fluid(s) from leaking through the inlet / outlets that would otherwise cause damage to the water treatment controller components. The cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet may each comprise a male-type connector or a female-type valve connector. A male-type connector may be configured to mate with a corresponding female-type connector, and each self-sealing valve may comprise a plate that is biased to seal the valve. When the cartridge is fastened to the controller unit, the male-type connectors mates with the female-type connectors so as to move the plates to an open position, thereby allowing fluid flow into, and out of, the respective water flow paths and treatment fluid flow paths. One or more of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, and the cartridge water outlet may be fixed to the cartridge. One or more of the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet may be fixed to the controller unit. Additionally / alternatively, one or more of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet may have a degree of float so as to allow lateral movement of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet. The cartridge of the water treatment controller may further comprise a cartridge wireless transmitter, and the controller unit may further comprise a controller unit wireless receiver. In this case, the test probe and the controller being communicatively coupled comprises the test probe being communicatively coupled to the cartridge wireless transmitter, the wireless receiver being communicatively coupled to the controller, and the cartridge wireless transmitter being configured to wirelessly transmit the measurement signal to the controller wireless receiver, so that the measurement signal provided by the test probe is received by the controller. Alternatively, the cartridge of the water treatment controller may further comprise a cartridge measurement signal connector, and the controller unit may further comprise a controller measurement signal connector. In this case, the test probe and the controller being communicatively coupled comprises the test probe being communicatively coupled to the cartridge measurement signal connector, the controller electrical signal connector being communicatively coupled to the controller, and the cartridge measurement signal connector being configured to transmit the measurement signal to the controller measurement signal connector by a physical connection, so that the measurement signal provided by the test probe is received by the controller. The controller upstream water inlet may be configured for connection to a water supply, and either the cartridge treatment fluid inlet is configured for connection to a treatment fluid supply, or the controller upstream treatment fluid inlet is configured for connection to a treatment fluid supply. In other words, the treatment fluid supply can be connected to either the cartridge or the controller unit. The treatment fluid pump mechanism may be a peristaltic treatment fluid pump mechanism or another suitable pump mechanism. The cartridge of the water treatment controller may further comprise a flow meter located on the cartridge water path, the flow meter configured to measure a flow rate of the water and to provide a flow rate measurement signal indicative of the measured flow rate to the controller. The cartridge fastener fitting and the controller fastener fitting may comprise a rack and pinion mechanism, and fastening the cartridge and controller unit together may cause a rack and a pinion of the rack and pinion mechanism to engage, rotating the pinion to thereby draw the cartridge and the controller unit closer together. The controller unit may further comprise posts extending from the controller unit. The cartridge may further comprise recesses configured to at least partially receive the posts when the cartridge and the controller unit are fastened together. In this case, the rack and pinion mechanism is configured to drive the posts to ride along ramps of the rack to draw the cartridge and controller unit closer together. In a second aspect, there is provide a cartridge for a water treatment controller, for example, the water treatment controller discussed above. The cartridge comprises a treatment fluid inlet and a treatment fluid outlet connected by a treatment fluid flow path, and a treatment fluid pump mechanism located on the treatment fluid flow path. The treatment fluid pump mechanism is operable to pump a treatment fluid along the treatment fluid flow path from the treatment fluid inlet to the treatment fluid outlet. The cartridge further comprises a water inlet and a water outlet connected by a water flow path, a water test chamber located on the water flow path such that water flowing along the water flow path flows into and out of the water test chamber, and a test probe configured to measure a property of water in the water test chamber and to provide a measurement signal indicative of the measured property. The cartridge further comprises a fastener fitting for allowing the cartridge to be releasably fastened to a controller unit of the water treatment controller. The treatment fluid pump mechanism may comprise a transmission coupling for coupling with a complementary transmission coupling of the controller unit such that the complementary transmission coupling may drive the transmission coupling which in turn causes the treatment fluid pump mechanism to pump the treatment fluid along the treatment fluid flow path. The treatment fluid pump mechanism may further comprise a pump motor configured to cause the treatment fluid pump mechanism to pump the treatment fluid along the treatment fluid flow path in response to the pump mechanism receiving a pump control signal. The cartridge may be configured to provide the measurement signal to a wireless transmitter of the cartridge, the wireless transmitter configured to wirelessly transmit the measurement signal for reception by a wireless receiver of the controller unit. Alternatively, the cartridge may be configured to provide the measurement signal to a measurement signal connector of the cartridge, the measurement signal connector configured to convey the measurement signal for reception by the controller unit. The treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet may each comprise a self-sealing valve configured to seal the valve, thereby stopping fluid flow into, and out of, the respective treatment fluid and water paths when the fastener fitting is not fastened to the controller unit of the water treatment controller, and open the valve, thereby allowing fluid flow into, and out of, the respective treatment fluid and water paths when the fastener fitting is fastened to the controller unit of the water treatment controller. The treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet may each comprise a male-type connector or a female-type connector. One or more of the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet may be fixed to the cartridge. Additionally / alternatively, one or more of the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet may have a degree of float so as to allow lateral movement of the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet. The cartridge may further comprise a flow meter located on the water path, the flow meter configured to measure a flow rate of the water and to provide a flow rate measurement signal indicative of the measured flow rate. The flow meter may be located on the water path between the water inlet and the water test chamber. The cartridge may further comprise a power supply configured to provide power to the test probe and the pump motor. In this case, the power supply is an electrical generator driven by the flow of water along the water path. The treatment fluid pump mechanism may be a peristaltic treatment fluid pump mechanism. The test probe may be configured to measure one or more of the pH of the water, the oxygen reduction potential of the water, and the temperature of the water. In a third aspect, there is provided a water treatment controller unit comprising an upstream water inlet and an upstream water outlet connected by an upstream water flow path, a downstream water inlet and a downstream water outlet connected by a downstream water flow path, and a controller configured to receive a measurement signal and to output a pump controller signal in response to the received measurement signal, the pump controller signal outputted to a wireless transmitter for onward wireless transmission to a pump mechanism or outputted to a measurement signal connector for onward wired transmission to the pump mechanism. The water treatment controller unit also comprises a fastener fitting for allowing a cartridge to be releasably fastened to the water treatment controller unit. The water treatment controller unit may further comprise an upstream treatment fluid inlet and an upstream treatment fluid outlet connected by an upstream treatment fluid flow path, and a downstream treatment fluid inlet and a downstream treatment fluid outlet connected by a downstream treatment fluid flow path. The water treatment controller unit may further comprise a pump motor of the pump mechanism, the pump motor provided with a transmission coupling for coupling with a complementary transmission coupling of the cartridge. The pump controller signal causes the pump motor to drive the transmission coupling for driving the complementary transmission coupling of the cartridge. The upstream water outlet and the downstream water inlet may each comprise a self-sealing valve configured to seal the valve, thereby stopping fluid flow into, and out of, the respective water paths when the fastener fitting is not fastened to the cartridge of the water treatment controller unit, and open the valve, thereby allowing fluid flow into, and out of, the respective water paths when the fastener fitting is fastened to the cartridge of the water treatment controller unit. The upstream water outlet and the downstream water inlet may each comprise a male-type connector or a female-type valve connector. The upstream water outlet and / or the downstream water inlet may be fixed to the water treatment controller unit. Additionally / alternatively, the upstream water outlet and / or the downstream water inlet may have a degree of float so as to allow lateral movement of the upstream water outlet and / or the downstream water inlet. The upstream treatment fluid inlet may comprise a connector configured for connection to a treatment fluid supply, and / or the upstream water inlet may comprise a connector configured for connection to a water supply. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention can be more readily understood, reference will now be made, by way of example only, to the accompanying drawings in which: Figure 1 is a schematic representation of a swimming pool and a swimming pool control system. Figure 2 illustrates a front perspective view of a swimming pool controller for use in the swimming pool control system of Figure 1. Figure 3 illustrates a front perspective view of the swimming pool controller with a front cover of the controller removed. Figure 4 illustrates a front perspective view of the uncovered swimming pool controller, wherein the main unit and the replaceable cartridge of the controller are shown separated. Figure 5 illustrates a bottom perspective view of the uncovered swimming pool controller, showing the fluid and electrical connections. Figure 6 illustrates an internal view of the swimming pool controller with the main unit and cartridge separated. Figure 7 illustrates another internal view of the swimming pool controller with the main unit and cartridge separated. Figure 8A illustrates an internal fluid flow diagram of the swimming pool controller. Figure 8B illustrates an external fluid flow diagram of the swimming pool controller. Figures 9A-9D illustrate the valve connections of fluid couplings between the cartridge and the main unit of the swimming pool controller. Figures 10A-10D illustrate how the cartridge is attached to the main unit of the swimming pool controller using a rack and pinion mechanism. Figures 11A-11D illustrate how the cartridge is removed from the main unit of the swimming pool controller using the rack and pinion mechanism. Figures 12A-12B illustrate details of the rack and pinion mechanism. Figure 13 illustrates the motor shaft and pump alignment of the swimming pool controller. DETAILED DESCRIPTION OF THE INVENTION An aim of the present invention is to improve water treatment control systems, for example swimming pool control systems, by enabling easier and more convenient servicing of the systems. Many swimming pool control systems include separately housed components that need to be individually serviced and replaced over time as they begin to fail. Individual servicing and replacement can be costly and inconvenient to pool owners. The swimming pool controller of the present invention has a main unit housing ‘dry’ components (e.g., some electronics, motors etc.), and a detachable cartridge housing the ‘wet’ and consumable components (e.g., pumps, monitoring probes etc.). The modular nature of the controller means that the cartridge can be easily removed from the main unit and swapped out for a new cartridge during servicing / repair, enabling all-in-one servicing and replacement. Advantageously, being able to replace the breakable controller components in one quick and easy step helps reduce servicing time and parts wastage, is more convenient for pool owners / maintenance staff / servicing, and also enables the use of swap-and-replace schemes. Furthermore, the setup anticipates breakdown of components during normal service and so the cartridge can be swapped out in advance before components begin to fail. An example embodiment of the present invention will now be described in the context of a swimming pool controller, although it will be understood that the present invention enjoys far greater applicability. Figure 1 shows a swimming pool 100 with such a swimming pool controller 105. The swimming pool 100 includes the main body of bathing water 110 that must be tested and treated to keep the bathing water to an acceptable quality. Namely, the cleanliness and the pH of the bathing water must be maintained. This is done by testing and treating the bathing water with a disinfectant such as chlorine (or a chlorine-producing chemical like bleach) and / or with an acid to adjust the pH level (such as hypochlorous acid). To this end, the swimming pool includes a recirculation system 115 with a recirculation path (indicated by the anticlockwise arrows in Figure 1). Water enters the recirculation system 115 from a drain 120 provided in the bottom of the swimming pool 100 and from a skimmer 125 (that traps debris to the side of the swimming pool 100 and allows the debris to be skimmed from the surface of the bathing water, usually through an access hatch 130). Bathing water returns to the main body 110 of the swimming pool 100 via one or more pool return inlets 135. A main pump 140 (or main pumps) pumps bathing water through the recirculation system 115 along the recirculation path which flows through a filter 145 that acts to clean the bathing water of contaminants. The bathing water passing through the recirculation system 115 also passes through the controller 105. The controller 105 measures properties of the bathing water and determines how the bathing water should be treated to ensure its cleanliness and / or pH through appropriate dosing of the disinfectant and / or the acid. The controller 105 does this by measuring the oxidation reduction potential (ORP) of the bathing water, which is a measure of the disinfectant in the bathing water, and / or by measuring the pH of the bathing water. When the disinfectant concentration is too low, the controller 105 causes disinfectant to be pumped from a disinfectant tank 150 to join the bathing water flow back to the pool return inlet 135. When the pH is too high, the controller 105 causes acid to be pumped from an acid tank 155 to join the bathing water flow back to the pool return inlet 135. Figure 2 shows an embodiment of a controller 205, for example the swimming pool controller 105 of Figure 1. The controller 205 is box like and comprises a front cover 210 which is provided with a window 215 to allow an electronic display 220 to be viewed. The front cover 210 is removable, as shown in Figure 3. Figure 3 in combination with Figure 4 show that, with the front cover 210 removed, the controller 205 comprises a main unit 225 (also known as a controller unit) and a detachable cartridge 230 that can be attached to the side of the main unit 225. Figure 4 shows that the cartridge 230 attaches to the main unit 225 via fastener fittings comprising a set of posts 235 that extend from the side of the main unit 225 (six in this embodiment) that are received within six holes 240 in the cartridge 230. The main unit 225 and the cartridge 230 are provided with a set of male / female fluid couplings 245 (six in this embodiment) positioned centrally in the area where the cartridge 230 is fastened to the main unit 225. The fluid couplings 245 are flanked by a pair of motor transmission couplings, namely a pair of drive shafts 250 extending from pump motors 320 provided in the main unit 225 and that are received in respective drive sockets 255 provided in the cartridge 230. Figure 4 also shows an electrical connection between the main unit 225 and the cartridge 230: namely, the cartridge 230 is provided with an electrical cable 260 that extends from the top of the cartridge 230 and that terminates in a plug 265 that may be plugged into an electrical socket 270 provided in the main unit 225. The electrical cable 260 allows one or two-way communication between the cartridge 230 and main unit 225, and may comprise a waterproof housing or coating. Figure 5 shows that the bottom of the main unit 225 is provided with a further set of fluid couplings 275 (six male couplings in this embodiment) as well as a set of electrical connectors 280. The set of electrical connectors 280 facilitate electrical communication to other parts of the swimming pool control system. For example, to a pool heating system, pool lighting, pool cover etc. Figures 6 and 7 show that the fluid couplings 275 provided on the bottom of the main unit 225 are linked to respective ones of the fluid couplings 245 on the side of the main unit 225 via hosing 285, and hence to the respective corresponding fluid couplings 245 of the cartridge 230 when the main unit 225 and the cartridge 230 are fastened together. Figures 6 and 7 also show the internal components of the cartridge 230 (the cartridge housing is not shown in Figures 6 and 7). The top and bottom of the cartridge 230 are each provided with a peristaltic pump 290 that sits behind the drive socket 255 that receives the drive shaft 250 of the main unit 225. Rotation of the drive shaft 250 will cause the corresponding drive socket 255 to rotate which drives the peristaltic pump 290. The two peristaltic pumps 290 are linked to four of the fluid couplings 245 (two per pump) via hosing 295, while the other two fluid couplings 245 are linked to a test chamber 305 via additional hosing 300. The test chamber 305 has an associated sensor probe 310 for measuring properties of the bathing water, and a flow meter 315 for measuring the flow rate of the bathing water flowing into the test chamber 305. The fluid flow paths within the cartridge 230 are shown more clearly in Figure 8A. The top peristaltic pump 290 is coupled to the acid tank 155 on the upstream side and to the path back to the pool return inlet 135 on the downstream side. Hence, the top peristaltic pump 290 may be operated to pump acid into the swimming pool 100 to lower the pH of the bathing water. The bottom peristaltic pump 290 is coupled to the disinfectant tank 150 on the upstream side and to the path back to the pool return inlet 135 on the downstream side. Hence, the bottom peristaltic pump 290 may be operated to pump disinfectant into the swimming pool 100 to increase the ORP of the bathing water. Figure 8A also shows that the peristaltic pumps 290 are coupled to the pump motors 320 provided in the main unit 225 via the drive shafts 250 and drive sockets 255. Hence, of the six fluid couplings 245 on the cartridge 230, one forms a cartridge acid inlet 325, one forms a cartridge acid outlet 330, one forms a cartridge disinfectant inlet 335 and one forms a cartridge disinfectant outlet 340. These inlets / outlets allow the acid and disinfectant to flow to and through the peristaltic pumps 290 and then back towards the main unit 225. For example, the cartridge acid inlet 325 and the cartridge acid outlet 330 are connected by a hose 295 thereby forming a cartridge acid path. The peristaltic pump 290 is located on the cartridge acid path. The cartridge disinfectant inlet 335 and the cartridge disinfectant outlet 340 are connected by a hose 295 thereby forming a cartridge disinfectant path. The other peristaltic pump 290 is located on the cartridge disinfectant path. The other two fluid couplings 245 on the cartridge 230 form a cartridge water inlet 345 and a cartridge water outlet 350 that allow bathing water to flow to the test chamber 305 and back to the main unit 225. For example, the cartridge water inlet 345 and the cartridge water outlet 350 are connected by a hose 300 thereby forming a cartridge water path. The test chamber 305 and flow meter 315 are located on the cartridge water path. The sensor probe 310 has multiple sensor tips 311 that extend into the bathing water passing through the test chamber 305 to allow multiple properties of the bathing water to be measured. These include the ORP, the pH and the temperature of the bathing water. The multiple sensor tips 311 measure the potential difference between each respective tip and the bathing water, and provide electrical signals indicative of the values measured. These signals are then provided to the main unit 225 via the electrical cable 260 and plug 265. The flow meter 315 provides an electrical signal indicative of the water flow rate into the test chamber 305, and this flow meter electrical signal is also provided to the main unit 225 via the electrical cable 260 and plug 265. The flow meter 315 provides a safety mechanism by monitoring the flow of the bathing water passing into the test chamber 305. The peristaltic pumps 290 can be controlled based on the received water flow rate signals so as to maintain even chemical distribution into the swimming pool 100 and prevent erroneous dosing. For example, dosing the acid and / or disinfectant into static bathing water can lead to a harmful buildup of the chemicals in the bathing water. As such, if the water isn’t flowing at a sufficient rate and / or if the chemical readings recorded by the sensor probe 310 are too high or out of range, the flow meter 315 sends a stop pumping signal to the main unit 225 of the controller 205 to stop the acid and / or disinfectant being pumped into the bathing water by the peristaltic pumps 290. Returning to Figures 6 and 7, Figures 6 and 7 also show the internal components of the main unit 225. The main unit 225 houses electronic circuitry that forms an electronic control unit 355 that functions to provide automatic management of the bathing water. The electronic control unit 355 can also provide water management on an as-and-when needed basis. The electronic control unit 335 comprises a power supply, relays, motor drivers and a voltage regulator (not shown). The electronic control unit 355 may also comprise a wireless transceiver (not shown) for wireless communication with a remote device (not shown), such as a mobile phone or laptop of the pool owner or maintenance person. Accordingly, the pool owner or maintenance person may control the chemical dosing via the remote device. Notifications of issues with the swimming pool 100 and / or low chemical supplies can also be sent to the remote device as needed. For example, a notification of the stop pumping signal may be sent to the remote device when the flow rate is too low. The cartridge 230 may also include a unique identification number (not shown) linked to a yearly service countdown timer (which helps prevent use of counterfeit cartridges). For example, the countdown times measures 365 days from installation of the cartridge 230, and sends a notification to the remote device towards the end of the 365 days indicating that the cartridge 230 should be changed before the end of the year. The yearly countdown service countdown timer may also be linked to a subscription service for automatic delivery of a new cartridge 230 each year. The pump motors 320 may be stepper motors and these stepper motors may be used to implement automatic ordering of new chemicals as needed. For example, the number of rotations of the stepper motor can be monitored and used to indicate how much of the chemical supplies are left. Low chemical supply notifications can then be sent to the remote device. The electronic control unit 355 is connected to the socket 270 that receives the plug 265 of the cartridge 230. Thus, the electronic control unit 355 receives the signals indicative of the ORP of the water, the pH of the water, the flow rate of the water and temperature of the water, from the sensor probe 310 and flow meter 315. The ORP and pH may be simply compared to threshold levels. The flow rate and temperature of the bathing water may also be compared to a threshold level. If the measured ORP level is too low, the electronic control unit 355 can issue a control signal to the disinfectant pump motor 320 to start operation of that pump motor 320. The disinfectant pump motor 320 will drive the lower peristaltic pump 290 such that disinfectant is pumped from the disinfectant tank 150 into the bathing water thereby increasing the ORP of the bathing water. The pump 290 may be operated for a fixed period of time. If the dose of disinfectant is not enough to move the ORP level above the threshold, this will be detected in a subsequent measurement cycle and so more disinfectant will be added to the bathing water. Hence, the bathing water will continue to be treated with additional disinfectant until the ORP level is acceptable. If the measured pH level is too high, the electronic control unit 355 can issue a control signal to the acid pump motor 320 to start operation of that pump motor 320. The acid pump motor 320 will drive the upper peristaltic pump 290 such that acid is pumped from the acid tank 155 into the bathing water thereby decreasing the pH of the bathing water. The pump 290 may be operated for a fixed period of time. If the dose of acid is not enough to drop the pH level below the threshold, this will be detected in a subsequent measurement cycle and so more acid will be added to the bathing water. Hence the bathing water will continue to be treated with additional acid until the pH level is acceptable. Fluid flow paths within the main unit 225 are shown most clearly in Figure 8A. There are the six side fluid couplings and six bottom fluid couplings on the main unit 225 which are linked together by hosing 285 to form six coupling pairs. Of the six coupling pairs, one pair includes a main unit acid upstream inlet 380 and a main unit acid upstream outlet 385 connected by a hose 285 thereby forming a main unit acid upstream fluid flow path, one pair includes a main unit acid downstream inlet 390 and a main unit acid downstream outlet 395 connected by a hose 285 thereby forming a main unit acid downstream fluid flow path, one pair includes a main unit disinfectant upstream inlet 400 and a main unit disinfectant upstream outlet 405 connected by a hose 285 thereby forming a main unit disinfectant upstream fluid flow path, and one pair includes a main unit disinfectant downstream inlet 410 and a main unit disinfectant downstream outlet 415 connected by a hose 285 thereby forming a main unit disinfectant downstream fluid flow path. Of the other two coupling pairs on the main unit 225, one includes a main unit water upstream inlet 420 and a main unit water upstream outlet 425 connected by a hose 285 thereby forming a main unit water upstream fluid flow path, and the other includes a main unit water downstream inlet 430 and a main unit water downstream outlet 435 connected by a hose 285 thereby forming a main unit water downstream fluid flow path. Figure 8B shows the fluid flow paths external to the controller 205 that connect the acid tank 155, the disinfectant tank 150 and the pool return inlet 135 to and from the six fluid couplings provided on the bottom of the main unit 225. Hosing 440 connects: the acid tank 155 to the main unit acid upstream inlet 380; the disinfectant tank 150 to the main unit disinfectant upstream inlet 400; the pool return inlet 135 to the main unit water upstream inlet 420; the main unit acid downstream outlet 395 to the pool return inlet 135; the main unit disinfectant downstream outlet 415 to the pool return inlet 135; and the main unit water downstream outlet 435 to the pool return inlet 135. Accordingly, when the main unit 225 and the cartridge 230 of the controller 205 are fastened together, there are three separate fluid flow paths - one for the acid, one for the disinfectant, and one for the bathing water being tested. In the acid flow path, acid flows from the acid tank 155 to the main unit acid upstream inlet 380, through to and out of the main unit acid upstream outlet 385 that connects with the cartridge acid inlet 325. The acid passes through the upper peristaltic pump 290, through the cartridge acid outlet 330 and into the connected main unit acid downstream inlet 390. The acid then passes out of the main unit acid downstream outlet 395 and to the pool return inlet 135. In the disinfectant flow path, disinfectant flows from the disinfectant tank 150 to the main unit disinfectant upstream inlet 400, through to and out of the main unit disinfectant upstream outlet 405 that connects with the cartridge disinfectant inlet 335. The disinfectant passes through the lower peristaltic pump 290, through the cartridge disinfectant outlet 340 and into the connected main unit disinfectant downstream inlet 410. The disinfectant then passes out of the main unit disinfectant downstream outlet 415 and to the pool return inlet 135. In the water flow path, bathing water flows from the recirculation path to the main unit water upstream inlet 420, through to and out of the main unit water upstream outlet 425 that connects with the cartridge water inlet 345. The water passes through the flow meter 315 and the test chamber 305, through the cartridge water outlet 350 and into the connected main unit water downstream inlet 430. The water then passes out of the main unit water downstream outlet 435 and to the pool return inlet 135. As discussed above, the acid and disinfectant are pumped around their respective fluid flow paths by the controlled peristaltic pumps 290. Bathing water flows along the water flow path under the control of the main swimming pool pump 140 of the recirculation system 115. Turning now to Figures 9A-D, a particular embodiment of the fluid couplings 245 between the main unit 225 and the cartridge 230 is shown. These figures are sections that show two of the fluid couplings 245; although the other four fluid couplings 245 are not shown, they have a corresponding design. The fluid couplings 245 have co-operating male parts 500 and female parts 505. In this embodiment the male parts 500 are provided by the cartridge 230 and the female parts 505 are provided by the main unit 225 (see also Figures 6 and 7), although other arrangements may be used. The advantage of this placement is that the O-ring of the male part 500 tends to wear down faster and so the male parts 500 are in need of more regular maintenance than the female parts 505. As such, placing all of the male parts 500 on the cartridge 230 enables easy, all-in-one replacement of these parts when swapping out the cartridge 230. Figures 9A and 9B show the male parts 500 and female parts 505 when the cartridge 230 is disconnected from the main unit 225. Figure 9B shows an enlargement of detail H in Figure 9A. In this state, the male parts 500 and female parts 505 automatically seal to stop water and / or chemicals (e.g., the acid and / or disinfectant) from leaking through the couplings 245. This is achieved using spring-biased valves. Advantageously, these spring-biased, self-sealing valves can enable the swimming pool recirculation system 115 to continue running when servicing the controller 205, if desired, thereby reducing disruption. The female part 505 has a valve 510 provided within its bore 515. A slide 520 is provided that has a base 525 at the open (outer) end of the female part 505 and a stem 530 that protrudes through a valve seat 535 provided in the bore 515 of the female part 505. An O-ring 540 is provided on the stem 530 that is urged against the valve seat 535 by a helical spring 545 (represented by the dotted lines in the female part 505) wound around the stem 530 on the other side of the valve seat 535. This seals the female part 505 when the cartridge 230 is disconnected from the main unit 225, stopping fluid flow through slots 555 (the slots 555 are not shown in Figure 9B). The fluid flow towards the female part 505 is shown by the upper left dashed arrow in Figure 9B. The stem 530 terminates with a blind end 550 at the valve seat 535 end. Slots 555 are provided in the side of the slide 520 adjacent the blind end 550. The male part 500 comprises an outer wall 560 that encircles a telescoping slide 565 that has an open end 570 at the distal (outer) end of the male part 500 and a blind end 575 at the proximal end of the male part 500. Slots 580 (not shown in Figure 9B) are provided in the side of the slide 565 adjacent the blind end 575. The outside of the blind end 575 is provided with an O-ring 585 and is biased by a helical spring 590 (represented by the dotted lines in the male part 500). The spring 590 presses on the blind end 575 to urge the O-ring 585 into a valve seat 595, thereby sealing the male part 500 when the cartridge 230 is disconnected from the main unit 225, stopping fluid flow through the slots 580. The fluid flow towards the male part 500 is shown by the lower right dashed arrow in Figure 9B. The valve seat 595 is formed by a shoulder 600 of the outer wall 560 of the male part 500 in a region where the internal bore of the male part 500 widens. Figures 9C and 9D show the fluid couplings 245 when the cartridge 230 is connected to the main unit 225. Figure 9D shows an enlargement of detail F in Figure 9C. As the cartridge 230 is pushed into engagement with the main unit 225, the male parts 500 of the fluid couplings 245 penetrate the female parts 505. The open ends 570 of the male slides 565 contact the bases 525 of the female slides 520. Continuing to press the cartridge 230 into the main unit 225 causes the slides 565, 520 to compress the helical springs 590, 545 such that the slides 565, 520 move back within their respective male and female parts 500, 505. It can be seen that the springs 590, 545 are compressed such that the O-rings 585, 540 of both the male parts 500 and female parts 505 are moved clear of the valve seats 595, 535. Additionally, the female slots 555 (indicated by the left hand dotted arrows in Figure 9D) in the female slides 520 move clear of the valve seat 535 such that fluid can flow into the female slides 520 and then into the male slides 565. Fluid can then exit the male slides 565 as the slots 580 (the slots 580 are indicated by the right hand dotted arrows in Figure 9D) in the male slides 565 are also moved clear of the valve seat 595 such that fluid may flow from the male slides 565 into the region where the bore of the male parts 500 widen. This (upstream) fluid flow direction is shown by the upper dashed arrows in Figure 9D. The lower dashed arrows in Figure 9D show the fluid flow in the reverse (downstream) direction from the male parts 500 provided on the cartridge 230 to the female parts 505 provided on the main unit 225. When the cartridge 230 is disconnected from the main unit 225, the male slides 565 and the female slides 520 move outwardly under the tension in the compressed helical springs 590, 545. This causes the O-rings 585, 540 to be urged against their respective valve seats 595, 535, thereby closing the valves and preventing fluid from leaking from the fluid couplings 245. To assist in connecting the cartridge 230 to the main unit 225, some of the female parts 505 and / or the male parts 500 of the fluid couplings 245 may have a degree of movement or float with respect to the main unit 225 or cartridge 230 that they are provided on. That is, the female parts 505 may be mounted to the main unit 225 in a way that permits some lateral movement, and / or the male parts 500 may be mounted to the cartridge 230 in a way that permits some lateral movement. This lateral movement is transverse to the flow directions of the fluid flow paths. The other female / male parts 505, 500 of the fluid couplings 245 are fixed to the main unit 225 or cartridge 230 that they are provided on such that they do not move with respect to the main unit 225 or cartridge 230. As an example of the degree of float, the male / female parts 500, 505 are surrounded by an annular gap 610 in the main unit / cartridge housing (e.g., see the solid arrows indicating the annular gap 610 surrounding the female parts 505 in Figure 9D). A shoulder 615 stops any axial movement of the floating male / female parts 500, 505 (i.e., in flow directions of the fluid flow paths). Thus, the cartridge 230 may be connected to the main unit 225 even when the fluid couplings 245 are not precisely aligned, for example due to manufacturing intolerances, and avoids the need for costly high-precision manufacturing of the male / female parts 500, 505. In one exemplary layout, Figures 6 and 7 show the main unit fluid couplings comprising four smaller fixed female parts 505a (no float), and two larger floating female parts 505b. The cartridge fluid couplings comprise four corresponding smaller floating male parts 500a (for connection with the four fixed females 505a), and two corresponding larger fixed male parts 500b (for connection with the two floating females 505b). Since the fixed parts 505a, 500b are not surrounded by an annular gap 610, they cover a smaller surface area of the outer surface of the main unit 225 or cartridge 230 they are fixed as compared to the floating parts 505b, 500a. As such, the combination of fixed and floating parts on each of the main unit 225 and cartridge 230 helps provide a space saving fluid coupling configuration. Figures 10A-10D show how the cartridge 230 is coupled to the main unit 225 using a rack and pinion mechanism 700 that ensures a good watertight connection between the fluid couplings 245. Figures 11A-11D show how the cartridge 230 is removed from the main unit 225 using the rack and pinion mechanism 700. Figures 12A-12B show the rack and pinion mechanism 700 in more detail. Advantageously, the rack and pinion mechanism 700 reduces the effort necessary to connect and remove the cartridge 230 from the main unit 225. The rack and pinion mechanism 700 also helps overcome issues with detritus and calcification build up on the cartridge 230 and main unit 225 that can hinder the connection / removal process. Figure 10A shows that the main unit 225 is provided with two sets of three aligned posts 235 that extend from the main unit 225 towards the cartridge 230. As can be seen in Figure 6, these posts 235 are received within six holes 240 provided in the cartridge 230. When the cartridge 230 is attached to the main unit 225, each set of three posts 235 passes through the associated holes 240 such that the distal ends 705 of the posts 235 pass into the interior of the cartridge 230. With the cartridge 230 held in place, a Torx key 710 (or a thumbwheel, not shown) may be turned to lock the cartridge 230 into place, as shown in Figure 10B (e.g., in the direction of arrow 715). Before the Torx key 710 is turned, the three posts 235 of each set of posts 235 are located between a series of three ramped supports 720 provided in the cartridge 230. Each set of three ramped supports 720 is provided on a rack 725, while the Torx key 710 is connected to a pair of pinions 730, with each pinion 730 driving one of the racks 725. Hence, turning the Torx key 710 actuates the rack and pinion mechanism 700 such that the ramped supports 725 move relative to the posts 235. The distal end 705 of each post 235 includes a cylindrical stub 735 that extends laterally from the post 235, as seen best in Figure 10A. When the cartridge 230 is held against or close to the main unit 225 ready to be attached to the main unit 225, the stubs 737 are aligned with but separated from the ramped supports 720 (see Figure 10B). Turning the Torx key 710 moves the ramped supports 720 towards the stubs 735. Eventually, the stubs 735 will contact the ramps 740 of the ramped supports 720 and ride along the ramps 740, thereby drawing the cartridge 230 into the main unit 225 and ensuring a firm connection between the fluid couplings 245. The ramps 740 of each ramped support 720 end with a lip and a concave top section 745 that is shaped and sized to receive the associated stub 735 and offer some resistance to the stub 735 moving free of the concave top section 745, thereby locking the cartridge 230 to the main unit 225 (see Figure 10C). Once the cartridge 230 is fastened to the main unit 225, the Torx key 510 may be removed, as shown in Figure 10D. Removal of the cartridge 230 from the main unit 225 is shown in Figures 11 A-11D. To remove the cartridge 230 from the main unit 225, the removable cover 210 is first taken off (the removable cover 210 is already removed in Figures 11 A-11D). As shown in Figure 11A, the Torx key 710 is inserted so that it can drive the rack and pinion mechanism 700. The Torx key 710 is turned in the opposite direction, as shown by arrow 750 in Figures 11 B.1 and 11 B.2 (Figures 11 B.1 and 11 B.2 are the same except that a section of the cartridge housing is removed in Figure 11 B.2 to more clearly show the rack and pinion mechanism 700). The Torx key 710 is turned, firmly at first, to allow the stubs 735 to ride over the lips of the concave top sections 745, as best seen between Figures 11 B.2 to 11C. Eventually, the stubs 735 will move clear of the ramped supports 720 such that the posts 235 may be withdrawn from the holes 240 and the cartridge 230 removed from the main unit 225, as shown in Figure 11D. The electrical cable 260 should be unplugged from the socket 270 before the cartridge 230 is fully removed from the main unit 225. Figures 12A and 12B show the rack and pinion mechanism 700 components in more detail. Figure 12A shows the pair of pinions 730 that engage with the Torx key 710. Figure 12A also shows annular gaps 610 around male parts 500 on the cartridge 230. Figure 12B shows the lip and a concave top section 745 of the ramps 740 resisting the associated stub 735 from moving free so as to lock the cartridge 230 to the main unit 225. When attaching the cartridge 230 to the main unit 225, the drive shaft 250 of each pump motor 320 must be received within and engaged by the drive socket 255 of the peristaltic pump 290 in the cartridge 230. The drive shaft 250 had a D-shape that is mirrored by the drive socket 255, such that the drive shaft 250 can turn the drive socket 255 and hence the peristaltic pump 290. To allow the cartridge 230 to be securely attached to the main unit 225, the D-shapes of the drive shaft 250 and drive socket 255 must be aligned to allow the drive shaft 250 to be received fully in in the drive socket 255. Figure 13 shows that the main unit 225 and the cartridge 230 are provided with D-shaped indicators 800 to show how the drive shaft 250 and drive socket 255 must be aligned prior to attaching the cartridge 230 to the main unit 225. The drive socket 255 of the cartridge 230 may be aligned using a plate alignment tool (not shown), for example, a plastic plate, that slots into recesses 805 of the drive socket 255. The swimming pool controller 205 may be mounted to a wall via a bracket fitting (not shown) on the rear of the controller 205. The bracket fitting mates with a complimentary wall fitting. Also, to allow access to components within the main unit 225, the main unit 225 has a removable front housing plate 900. A gasket 905 is positioned within a lip 910 of the main unit housing so as to provide a water resistant seal for the main unit 225, thereby stopping fluids from entering the interiors of the main unit 225 and causing water damage. Alternatives A person skilled in the art will appreciate that the above embodiments may be varied in many different respects without departing from the scope of the present invention that is defined by the appended claims. Each of the below variations is compatible with each and every other variation below, unless stated otherwise. The swimming pool control system shown in the figures and described above comprises two treatment fluids - an acid for adjusting the pH level of the water, and a disinfectant for treating the water. However, the swimming pool control system can also be operated with just one of these treatment fluids. In which case, the swimming pool controller 205 only requires two fluid flow paths instead of three (one path for the treatment fluid and the other path for the bathing water). As such, the cartridge 230 here will comprise four fluid couplings 245, one peristaltic pump 290, and one drive socket 255 for that peristaltic pump 290. The main unit 225 will comprise four of the side fluid couplings 245 and four of the bottom fluid couplings 275, as well as one pump motor 320 and drive shaft 250. In other examples, the swimming pool control system may control more than two treatment fluids, e.g., salt may also be used to treat the bathing water, in which case the number of fluid flow paths and components of the controller 205 will increase accordingly. In addition, in the figures and description above, the acid and disinfectant are described as fluids. However, the acid and / or disinfectant could be a solid tablet housed within the acid tank 155 and / or disinfectant tank 150 and a liquid (such as water) added to dissolve the solid tablet(s). The swimming pool controller 205 shown in the figures and described above comprises two pump motors 320 and drive shafts 250 provided in the main unit 225. However, these two pump motors 320 and drive shafts 250 (or other number of pump motors 320 and drive shafts 250, depending on the number of treatment fluids being controlled in the system) can instead be provided in the cartridge 230. In this example, the pump control signals from the electronic control unit 355 of the main unit 225 are provided to the pump motors 320 via the electrical cable 260. I.e., when the plug 265 of the electrical cable 260 is plugged into the socket 270 of the main unit 225, the pump control signals are passed across to the pump motors 320 inside the cartridge 230, whilst the water measurement signals (and / or flow rate signals) are passed in the other direction to the electronic control unit 355 of the main unit 225. So far, the swimming pool controller 205 has been described as comprising the electrical cable 260 for providing the water measurement signals, flow rate signals and / or pump control signals. An optical cable may instead be used for providing the water measurement signals, flow rate signals and / or pump control signals. Instead of, or additional to, wired communication, a wireless communication may be used. For example, the cartridge 230 may comprise a wireless transmitter coupled to the sensor probe 310 and flow meter 315. The wireless transmitter wirelessly transmits the water measurement signals and / or flow rate signals over to a wireless receiver of the main unit 225. The wireless receiver is coupled with the electronic control unit 355 so as to pass the signals onto the electronic control unit 355 for pump control. Depending on whether the pump motors 320 and drive shafts 250 are provided in the main unit 225 or the cartridge 230, the pump control signals can be sent by wired or wireless connection. For example, where the pump motors 320 and drive shafts 250 are provided in the main unit 225 (like in the examples shown in the figures), the pump control signals are provided to the pump motors 320 via an electrical cable coupling the electronic control unit 355 and the pump motors 320 inside the main unit 225. However, if the pump motors 320 and drive shafts 250 are provided within the cartridge 230 (not shown in the figures), then the pump control signals are sent wirelessly from the main unit 225 to the cartridge 230. In this case, the main unit 225 also comprises a wireless transmitter, and the cartridge 230 also comprises a wireless receiver (or the main unit 225 and the cartridge 230 each comprise a wireless transceiver). The wireless transmitter of the main unit 225 wirelessly transmits the pump control signals across to the wireless receiver of the cartridge 230 in response to receiving the wireless water measurement and / or flow rate signals from the cartridge 230. The pump control signals received at the wireless receiver in the cartridge 230 are then passed to the pump motors 320 via an electrical cable coupling the wireless receiver and the pump motors 320 within the cartridge 230. In wireless communication examples, the cartridge 230 may comprise its own power supply to provide power to one or more of the sensor probe 310, the flow meter 315, the wireless transmitter, the wireless receiver and the pump motors 320 (depending on the positioning of the components in the main unit / cartridge). For example, this power supply is an electrical generator that is driven by the water flow along the water path. The flow meter 315 is described as part of the swimming pool controller 205 throughout the figures and above description, but is an optional component of the controller 205. The cartridge 230 of the swimming pool controller 205 has been described as including peristaltic pumps 290. However, any other suitable pump may be used in the controller. For example, a diaphragm pump, a piston pump or a gear pump to name a few. Furthermore, the peristaltic pumps 290 have been described as being provided at the top and bottom of the cartridge 230 in the above examples. However, the peristaltic pumps 290 could instead be provided at different locations in the cartridge 230, e.g., side by side, instead of upper and lower, etc. Similarly, the acid and disinfectant flow paths have been described as the top and bottom flow paths respectively in the above examples (e.g., see Figures 8A and 8B). However, these acid and disinfectant flow paths (and the water flow path) can also be provided in different orientations within the controller 205. In the above description (see Figures 6 and 7 in particular), all of the male parts 500 of the fluid couplings 245 are provided by the cartridge 230 and all of the female parts 505 of the fluid couplings 245 are provided by the main unit 225. However, as previously stated, other arrangements may be used. For example, the controller 205 may instead comprise all of the female parts 505 on the cartridge 230 and all of male parts 500 on the main unit 225. Alternatively, there may be a mix of both male parts 500 and female parts 505 on each of the cartridge 230 and the main unit 225. For example, Figure 12A shows four male parts 500 and two female parts 505 on the cartridge 230 (and the main unit 225 would have four corresponding female parts 505 and two corresponding male parts 500 (not shown)). The main unit 225 of the controller 205 is shown and described above as comprising four sections of the treatment fluid flow paths - the main unit acid upstream flow path, the main unit acid downstream flow path, the main unit disinfectant upstream flow path, and the main unit disinfectant downstream flow path - which link to the treatment tanks 150, 155 (e.g., see Figure 8B). However, in some examples (not shown), the main unit 225 need not comprise these four sections of the treatment paths. Instead, the acid tank 155 may connect directly to the cartridge acid inlet 325, the cartridge acid outlet 330 may connect directly to the pool return inlet 135, the disinfectant tank 150 may connect directly to the cartridge disinfectant inlet 335, and the cartridge disinfectant outlet 340 may connect directly to the pool return inlet 135, so as to form the acid and disinfectant flow paths. The swimming pool controller 205 shown in the figures and described above comprises a rack and pinion mechanism 700 for fastening the cartridge 230 and the main unit 225 together, the rack and pinion mechanism 700 actuated by the manual turning of a thumbwheel or Torx key 710. However, the rack and pinion mechanism 700 could also be 5 actuated by a motor or a thumbwheel etc. Other suitable fastenings could also be used to fasten the cartridge 230 and the main unit 225 together. For example, the main unit 225 could comprise latches on the top and bottom of the main unit 225 which latch into latch retainers on the cartridge 230. Other fitting examples between the main unit 225 and the cartridge 230 include a snap connection, a screw fit, Velcro fastenings, cam mechanisms 10 and clamp mechanisms to name few. The main embodiment described and shown here is a swimming pool controller 205. However, such a controller 205 is not just compatible for use with swimming pools 100. It may also be used to control spas, Jacuzzis, hot tubs, natural pools and other bathing facilities. 15

Claims

1. A cartridge for a water treatment controller, the cartridge comprising:a treatment fluid inlet and a treatment fluid outlet connected by a treatment fluid flow path;a treatment fluid pump mechanism located on the treatment fluid flow path, wherein the treatment fluid pump mechanism is operable to pump a treatment fluid along the treatment fluid flow path from the treatment fluid inlet to the treatment fluid outlet;a water inlet and a water outlet connected by a water flow path;a water test chamber located on the water flow path such that water flowing along the water flow path flows into and out of the water test chamber;a test probe configured to measure a property of water in the water test chamber and to provide a measurement signal indicative of the measured property; anda fastener fitting for allowing the cartridge to be releasably fastened to a controller unit of the water treatment controller.

2. The cartridge of claim 1, wherein the treatment fluid pump mechanism comprises a transmission coupling for coupling with a complementary transmission coupling of the controller unit such that the complementary transmission coupling may drive the transmission coupling which in turn causes the treatment fluid pump mechanism to pump the treatment fluid along the treatment fluid flow path.

3. The cartridge of claim 1 or claim 2, wherein the treatment fluid pump mechanism further comprises a pump motor configured to cause the treatment fluid pump mechanism to pump the treatment fluid along the treatment fluid flow path in response to the pump mechanism receiving a pump control signal.

4. The cartridge of any preceding claim, wherein one of:the cartridge is configured to provide the measurement signal to a wireless transmitter of the cartridge, the wireless transmitter configured to wirelessly transmit the measurement signal for reception by a wireless receiver of the controller unit, orthe cartridge is configured to provide the measurement signal to a measurement signal connector of the cartridge, the measurement signal connector configured to convey the measurement signal for reception by the controller unit.

5. The cartridge of any preceding claim, wherein the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet each comprise a self-sealing valve configured to:seal the valve, thereby stopping fluid flow into, and out of, the respective treatment fluid and water paths when the fastener fitting is not fastened to the controller unit of the water treatment controller; andopen the valve, thereby allowing fluid flow into, and out of, the respective treatment fluid and water paths when the fastener fitting is fastened to the controller unit of the water treatment controller.

6. The cartridge of any preceding claim, wherein the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet each comprise a male-type connector or a female-type connector.

7. The cartridge of any preceding claim, wherein one or more of the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet are fixed to the cartridge; and / orwherein one or more of the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet have a degree of float so as to allow lateral movement of the treatment fluid inlet, the treatment fluid outlet, the water inlet and the water outlet.

8. The cartridge of any preceding claim further comprising a flow meter located on the water path, the flow meter configured to measure a flow rate of the water and to provide a flow rate measurement signal indicative of the measured flow rate, and optionally, wherein the flow meter is located on the water path between the water inlet and the water test chamber.

9. The cartridge of any preceding claim further comprising a power supply configured to provide power to the test probe and the pump motor, and optionally, wherein the power supply is an electrical generator driven by the flow of water along the water path.

10. The cartridge of any preceding claim, wherein the treatment fluid pump mechanism is a peristaltic treatment fluid pump mechanism.

11. The cartridge of any preceding claim, wherein the test probe is configured to measure one or more of: the pH of the water, the oxygen reduction potential of the water, and the temperature of the water.

12. A water treatment controller unit comprising:an upstream water inlet and an upstream water outlet connected by an upstream water flow path;a downstream water inlet and a downstream water outlet connected by a downstream water flow path;a controller configured to receive a measurement signal and to output a pump controller signal in response to the received measurement signal, the pump controller signal outputted to a wireless transmitter for onward wireless transmission to a pump mechanism or outputted to a measurement signal connector for onward wired transmission to the pump mechanism;a fastener fitting for allowing a cartridge to be releasably fastened to the water treatment controller unit.

13. The water treatment controller unit of claim 12 further comprising:an upstream treatment fluid inlet and an upstream treatment fluid outlet connected by an upstream treatment fluid flow path; anda downstream treatment fluid inlet and a downstream treatment fluid outlet connected by a downstream treatment fluid flow path.

14. The water treatment controller unit of claim 12 or claim 13 further comprising a pump motor of the pump mechanism, the pump motor provided with a transmission coupling for coupling with a complementary transmission coupling of the cartridge, andwherein the pump controller signal causes the pump motor to drive the transmission coupling for driving the complementary transmission coupling of the cartridge.

15. The water treatment controller unit of any one of claims 12-14, wherein the upstream water outlet and the downstream water inlet each comprise a self-sealing valve configured to:seal the valve, thereby stopping fluid flow into, and out of, the respective water paths when the fastener fitting is not fastened to the cartridge of the water treatment controller unit; andopen the valve, thereby allowing fluid flow into, and out of, the respective water paths when the fastener fitting is fastened to the cartridge of the water treatment controller unit.

16. The water treatment controller unit of any one of claims 12-15, wherein the upstream water outlet and the downstream water inlet each comprise a male-type connector or a female-type valve connector.

17. The water treatment controller unit of any one of claims 12-16, wherein the upstream water outlet and / or the downstream water inlet are fixed to the water treatment controller unit; and / orwherein the upstream water outlet and / or the downstream water inlet have a degree of float so as to allow lateral movement of the upstream water outlet and / or the downstream water inlet.

18. The water treatment controller unit of any one of claims 12-17, wherein the upstream treatment fluid inlet comprises a connector configured for connection to a treatment fluid supply, and / or wherein the upstream water inlet comprises a connector configured for connection to a water supply.

19. A water treatment controller comprising a cartridge and a controller unit, the cartridge comprising:a cartridge treatment fluid inlet and a cartridge treatment fluid outlet connected by a cartridge treatment fluid flow path;a treatment fluid pump mechanism located on the cartridge treatment fluid flow path, wherein the treatment fluid pump mechanism is operable to pump a treatment fluid along the cartridge treatment fluid flow path from the cartridge treatment fluid inlet to the cartridge treatment fluid outlet;a cartridge water inlet and a cartridge water outlet connected by a cartridge water flow path;a water test chamber located on the cartridge water flow path such that water flowing along the cartridge water flow path flows into and out of the water test chamber;a test probe configured to measure a property of water in the water test chamber and to provide a measurement signal indicative of the measured property to a controller of the controller unit; anda cartridge fastener fitting;the controller unit comprising:a controller upstream water inlet and a controller upstream water outlet connected by a controller upstream water flow path;a controller downstream water inlet and a controller downstream water outlet connected by a controller downstream water flow path; anda controller unit fastener fitting, wherein the cartridge fastener fitting and the controller unit fastener fitting co-operate to allow the cartridge to be fastened to and unfastened from the controller unit;wherein the treatment fluid pump mechanism further comprises a pump motor located in the controller unit or in the cartridge; andwherein, when the cartridge is fastened to the controller unit:the controller upstream water outlet makes fluid connection with the cartridge water inlet, and the cartridge water outlet makes fluid connection with the controller downstream water inlet, such that water can flow along the controller upstream water flow path, the cartridge water flow path and the controller downstream water flow path;the test probe and the controller are communicatively coupled so that the measurement signal provided by the test probe is received by the controller, and the controller and the pump motor are communicatively coupled so that a pump control signal outputted by the controller is received by the pump motor; andthe controller is configured to produce the pump controller signal to control the pump motor in response to the received measurement signal, the pump control signal causing the pump motor to drive the treatment fluid pump mechanism to pump the treatment fluid along the cartridge treatment fluid flow path.

20. The water treatment controller of claim 19, wherein the controller unit further comprises:a controller upstream treatment fluid inlet and a controller upstream treatment fluid outlet connected by a controller upstream treatment fluid flow path;a controller downstream treatment inlet and a controller downstream treatment fluid outlet connected by a controller downstream treatment fluid flow path;and when the cartridge is fastened to the controller unit:the controller upstream treatment fluid outlet makes fluid connection with the cartridge treatment fluid inlet, and the cartridge treatment fluid outlet makes fluid connection with the controller downstream treatment fluid inlet, such that the treatment fluid can flow along the controller upstream treatment fluid flow path, the cartridge treatment fluid flow path and the controller downstream treatment fluid flow path.

21. The water treatment controller of claim 19 or claim 20, wherein one or more of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet each comprise a self-sealing valve configured to:seal the valve, thereby stopping fluid flow into, and out of, the respective water flow paths and treatment fluid flow paths when the cartridge fastener fitting is not fastened to the controller unit fastener fitting; andopen the valve, thereby allowing fluid flow into, and out of, the respective water flow paths and treatment fluid flow paths when the cartridge fastener fitting is fastened to the controller unit fastener fitting.

22. The water treatment controller of any one of claims 19 - 21, wherein the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet each comprise a male-type connector or a female-type valve connector.

23. The water treatment controller of any one of claims 19-22, wherein one or more of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, and the cartridge water outlet are fixed to the cartridge, and wherein one or more of the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet are fixed to the controller unit; and / orwherein one or more of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet have a degree of float so as to allow lateralmovement of the cartridge treatment fluid inlet, the cartridge treatment fluid outlet, the cartridge water inlet, the cartridge water outlet, the controller upstream water inlet, the controller upstream water outlet, the controller downstream water inlet and the controller downstream water outlet.

24. The water treatment controller of claims 22 or 23 when dependent on claim 20, wherein a male-type connector is configured to mate with a corresponding female-type connector, and wherein each self-sealing valve comprises a plate that is biased to seal the valve; andwherein, when the cartridge is fastened to the controller unit, the male-type connectors mates with the female-type connectors so as to move the plates to an open position, thereby allowing fluid flow into, and out of, the respective water flow paths and treatment fluid flow paths.

25. The water treatment controller of any one of claims 19-24, wherein the cartridge further comprises a cartridge wireless transmitter, and the controller unit further comprises a controller unit wireless receiver; andwherein the test probe and the controller being communicatively coupled comprises the test probe being communicatively coupled to the cartridge wireless transmitter, the wireless receiver being communicatively coupled to the controller, and the cartridge wireless transmitter being configured to wirelessly transmit the measurement signal to the controller wireless receiver, so that the measurement signal provided by the test probe is received by the controller.

26. The water treatment controller of any one of claims 19-24, wherein the cartridge further comprises a cartridge measurement signal connector, and the controller unit further comprises a controller measurement signal connector; andwherein the test probe and the controller being communicatively coupled comprises the test probe being communicatively coupled to the cartridge measurement signal connector, the controller electrical signal connector being communicatively coupled to the controller, and the cartridge measurement signal connector being configured to transmit the measurement signal to the controller measurement signal connector by a physical connection, so that the measurement signal provided by the test probe is received by the controller.

27. The water treatment controller of any one of claims 19-26, wherein the controller upstream water inlet is configured for connection to a water supply, and wherein one of:the cartridge treatment fluid inlet is configured for connection to a treatment fluid supply, orthe controller upstream treatment fluid inlet is configured for connection to a treatment fluid supply.

28. The water treatment controller of any one of claims 19-27, wherein the treatment fluid pump mechanism is a peristaltic treatment fluid pump mechanism.

29. The water treatment controller of any one of claims 19-28, wherein the cartridge further comprises a flow meter located on the cartridge water path, the flow meter configured to measure a flow rate of the water and to provide a flow rate measurement signal indicative of the measured flow rate to the controller.

30. The water treatment controller of any one of claims 19-29, wherein the cartridge fastener fitting and the controller fastener fitting comprise a rack and pinion mechanism; andwherein fastening the cartridge and controller unit together causes a rack and a pinion of the rack and pinion mechanism to engage, rotating the pinion to thereby draw the cartridge and the controller unit closer together.

31. The water treatment controller of claim 30, wherein the controller unit further comprises posts extending from the controller unit, and the cartridge further comprises recesses configured to at least partially receive the posts when the cartridge and the controller unit are fastened together, the rack and pinion mechanism configured to drive the posts to ride along ramps of the rack to draw the cartridge and controller unit closer together.s

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