An overflow valve for a drainage hole and a method for preventing water overflow from a drainage hole

Abstract

An overflow valve (100) for a drainage hole, the overflow valve (100) comprising - an elongated buoyant member (10) comprising a top (12), a bottom (14), and two or more tracks (16) arranged along the elongated buoyant member (10) between the top (12) and the bottom (14); wherein the elongated buoyant el-5 ement (10) has a positive buoyancy in water, - two or more gliding rods (20) configured for engaging the two or more tracks (16); - a first stopping member (30) configured for being connected to a frame of the drainage hole, the first stopping member (30) comprising a hole (32); 10 wherein the elongated buoyant member (10) is slidable along the two or more gliding rods (20) with changing water level, the elongated buoyant member (10) being slidable between two states: - a blocked state, where the top (12) engages the hole (32) thereby preventing water overflow, and 15 - an open state, where the top (12) and the hole (32) are apart.

Description

[0001] An overflow valve for a drainage hole and a method for preventing water overflow from a drainage hole

[0002] Field of the Invention

[0003] The present invention relates to an overflow valve for a drainage hole for preventing a drainage hole from overflowing. The invention further relates to an overflow valve for monitoring the conditions of and water quality in the drainage hole.

[0004] The present invention, furthermore, relates to a method for preventing water overflow from a drainage hole.

[0005] Background of the Invention

[0006] Sewers and other conduit systems for carrying off water typically comprises a hole or an opening for the removal of water and wastewater from enclosed volumes or surfaces, such as buildings or roads, to avoid flooding. A pipe or a conduit is used to carry away waste matter and water such as rainwater from the enclosed volumes or surface.

[0007] These drainage holes may further provide access to and be used as an access point for an underground sewer system, where the drainage holes enable pipe cleaning, blockage removal and allow condition assessment inspections and maintenance of the pipes by maintenance crews.

[0008] Drainage holes are often exposed to clogging and lack of precise monitoring of the condition of the sewer or conduit system, which lead to inefficient water management in the system and increased flood risk during periods of e.g., heavy rain, where excess water enters the sewer system, or where the main line gets stopped up causing the drainage hole to overflow. The overflow of a drainage hole may release raw sewage, also called sanitary sewer overflows (SSOs), which can contaminate water, causing serious water quality problems, and back-up into homes, causing property damage. The SSOs are further a risk to public health, since the overflows are made of human and industrial waste carrying bacteria and parasites, which may cause illnesses.

[0009] In addition, many systems require manual inspections to assess the condition of the sewer or conduit system, which is time consuming and ineffective. There is therefore a need for a method and a system that can prevent a drainage hole from overflowing and monitor the condition of the sewer or conduit system without the need of manual inspections.

[0010] Object of the Invention

[0011] One objective of the present disclosure is to provide an overflow valve that can prevent a drainage hole from overflowing, and which may further monitor the conditions of and / or water quality in the drainage hole without the need of manual inspections.

[0012] Another object is to provide a method for preventing a water overflow drainage hole.

[0013] Description of the Invention

[0014] One objective of the invention is achieved by an overflow valve for a drainage hole. The overflow valve comprising

[0015] - an elongated buoyant member comprising a top, a bottom, and two or more tracks arranged along the elongated buoyant member between the top and the bottom; wherein the elongated buoyant element has a positive buoyancy in water,

[0016] - two or more gliding rods configured for engaging the two or more tracks; - a first stopping member configured for being connected to a frame of the drainage hole, the first stopping member comprising a hole;

[0017] wherein the elongated buoyant member is slidable along the two or more gliding rods with changing water level, the elongated buoyant member being slidable between two states:

[0018] - a blocked state, where the top engages the hole thereby preventing water overflow, and

[0019] - an open state, where the top and the hole are apart.

[0020] Thereby the elongated buoyant member can move between the open state, the blocked state and any intermediate states with a changing water level in the drainage hole.

[0021] When the water level in the drainage hole increases the elongated buoyant member slides along the two or more gliding rods towards the first stopping member, and when the water level in the drainage hole reaches a maximum, the elongated buoyant member is in the blocked state, where the top of the elongated buoyant member engages and blocks the hole in the first stopping member, thereby stopping water inflow to the drainage hole and preventing water overflow from the drainage hole. Thus, the overflow valve automatically closes off the drainage hole, as the water pressure from beneath the elongated buoyant member presses the top against the hole of the first stopping member, when the water level in the drainage hole reaches a critical level that may result in an overflow from the drainage hole.

[0022] When the water level in the drainage hole decreases the elongated buoyant member slides along the two or more gliding rods away from the first stopping member, moving the top of the elongated buoyant member away from the hole in the first stopping member, where the elongated buoyant member is in the open state, thereby allowing a water inflow to the drainage hole. Thus, when the water pressure from beneath the elongated buoyant member decreases, then the overflow valve automatically opens, and the drainage hole can again receive a water inflow.

[0023] The water inflow to the drainage hole may be a water inflow from the surroundings above the drainage hole, such as rainwater and / or seawater from e.g., a storm.

[0024] The two or more gliding rods provides a trajectory for the movement of the elongated buoyant member in the drainage hole, and the two or more gliding rods may be attached to the first stopping member, thereby controlling the trajectory of the elongated buoyant member relative to the hole of the first stopping member. The two or more gliding rods may further be slidably connected to the two or more tracks.

[0025] The first stopping member may further comprise fasteners for attaching the overflow valve to a frame of the drainage hole, thereby ensuring the overflow valve is stable and stays in position within the drainage hole. The overflow valve can, thus, be installed in existing drainage holes, and may be integrated in existing sewer systems without the need of a greater redesign or reconstruction.

[0026] The drainage hole may be a manhole, a utility hole, a maintenance hole, or any other sewer hole for sewer systems configured for carrying away water from enclosed volumes or surfaces. These types of holes, in particular manholes, are typically used as an access point for an underground sewer system, and their primary function is to provide access to pipes for cleaning, removing blockages, and allow condition assessment inspections and maintenance by maintenance crews. However, the drainage hole may also be a drainage hole for a house drain system, and any other drainage hole for a conduit system configured for carrying away water from enclosed volumes or surfaces. The overflow valve may be installed in a drainage hole having a diameter in the range of 5 to 1500 mm and preferably in the range of 15 to 800 mm. At smaller diameters than the mentioned numbers, the flow past the elongated buoyant member will be rather low and at larger diameters than the mentioned diameters it may be necessary to apply additional fastening means such as additional anchors to ensure that the overflow valve can withstand the force generated from the water pressure.

[0027] The two or more tracks may be parallel to each other and thus the two or more gliding rods must in this case be parallel in the same direction. If the overall direction of the drainage hole is parallel with the gravitation vector, then the two or more tracks and the two or more gliding rods will typically be parallel to the gravitation vector as it will enable the elongated buoyant member to slide easier up and down with changes to the water level. The overflow valve will work even if the overflow wall is installed in a drainage hole which has a general orientation which is angled relative to the gravitation vector, however the risk of the elongated buoyancy member not moving downwardly with decreasing water height will increase with increasing angle relative to the gravitation vector.

[0028] The two or more tracks and the two or more gliding rods may extend along a substantially straight line.

[0029] The drainage hole may be a drainage well.

[0030] In some embodiments, the overflow valve may have dimensions fitting the standard dimensions of public drainage holes to enable installation in existing sewer systems.

[0031] The two or more tracks of the elongated buoyant member may be shaped in the elongated buoyant member as two or more indents, wherein the two or more gliding rods are arranged in the two or more indents, thereby providing a larger contact surface between the elongated buoyant member and the two or more gliding rods, which ensures a tighter grip between the elongated buoyant member and the gliding rods. Thereby, the elongated buoyant member is held firmly and trapped between the two or more gliding rods.

[0032] The elongated buoyant element has a positive buoyancy in water. Thereby enabling the elongated buoyant member to float on the water surface in the drainage hole. The buoyancy can be controlled by changing the density of the elongated buoyant element such that the elongated buoyant element is sufficiently below the water surface in order to measure with one or more sensors.

[0033] Preferable the elongated buoyant member has a buoyancy in water that allows approximately , 14, 1 / 2, or between and 14 of the elongated buoyant member to be submerged in water. In a preferred embodiment, the elongated buoyant member has buoyancy in water that allows approximately 14 of the elongated buoyant member to be submerged in water. This enables as this allow a sensor unit arranged in the bottom of the elongated buoyant member to be in contact with the water, which is a requirement for the sensor unit to be able to measure the various different water quality parameters such as pH-value and temperature.

[0034] A further advantage of a partially water submerged elongated buoyant member is that the one or more sensors may be arranged partly above and / or partly below the water depending on the parameter to be measured in the drainage hole, thereby enabling accurate measurement and data transmission.

[0035] In an embodiment, the top of elongated buoyant member may have oblique edges or a substantially spherical shape or a substantially cone shape. This prevents clogging of the overflow valve by e.g., leaves, branches, trash, waste matter, and sediments, because the sloping surfaces of the top allows the clogging materials to be automatically removed from the top, as the clogging materials glide along the sloping surfaces. Thereby, providing a self-cleaning overflow valve and ensuring a reliable operation without the risk of clogging.

[0036] In another embodiment, the elongated buoyant member may comprise a coating providing the elongated buoyant member with a reduced surface friction, such as a rubber coating, natural rubber coating, an elastomer coating or a polymer coating providing the elongated buoyant member with a reduced surface friction. Thereby preventing clogging materials and other residues from getting stuck on the top of the elongated member and ensuring a reliable operation without the risk of clogging. The coating further ensures that the elongated buoyant member glides more smoothly along the two or more gliding rods.

[0037] In another embodiment, the bottom of the elongated buoyant member may have oblique edges or a substantially spherical shape or a substantially cone shape or a shape similar to the shape of the top. Thereby, the bottom of the elongated buoyant member may always be under water. This is advantageous in embodiments where the bottom comprises a sensor unit comprising one or more sensors for measuring water level and / or water quality such as pH-value, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), nutrients, total nitrogen (TN), Total phosphorus (TP), temperature, organic material, microbiological parameters, metal content, organic micropollutants, oil content, micro plastics, nano plastics, grease content, pharmaceutical pollution, and / or turbidity, because the sensor unit may always be in contact with the water in the drainage hole, thereby obtaining accurate measurements of water level and water quality, and transmitting data to a central control unit for remote reading of the drainage hole condition.

[0038] The one or more sensors may measure one or more of the water quality parameters mentioned above but is not limited to these. Measuring these water quality parameters may be advantageous for the following reasons:

[0039] - The pH-value indicates how acidic or alkaline the wastewater is. This is important as extreme pH values can damage aquatic organisms and affect water treatment processes;

[0040] - The biochemical oxygen demand (BOD) measures the amount of oxygen consumed by microorganisms during break down organic material in the water. A high BOD value indicates high levels of organic contamination;

[0041] - The chemical oxygen demand (COD) measures the total amount of chemical substances in waste water that can be oxidized and gives an indication of the total amount of organic and inorganic contamination;

[0042] - The suspended solids (SS) is a measure of the amount of suspended solids in the waste water which may lead to sludge loading and clogging in water treatment plants;

[0043] - Nutrients is a measure of any kind of nutrients for plants or algae or similar and will help determine whether there is a nearby large polluter of nutrients;

[0044] - The total nitrogen (TN) is a measure of the nitrogen content, including ammonia, nitrite, nitrate and organic nitrogen, which is important as excess nitrogen may lead to eutrophication of aquatic environments;

[0045] - The total phosphorus (TP) is a measure of the phosphorus content, phosphorus is also a nutrient that can lead to eutrophication and is therefore monitored to prevent algae growth in the aquatic environments receiving the water;

[0046] - The temperature affects the activity of microorganisms in wastewater and may also affect the solubility of gases such as oxygen in the water; - The microbiological parameters is a measure of the presence of pathogens, thereby monitoring pathogens such as bacteria, viruses and parasites, especially E. coli, which is an indicator of fecal contamination;

[0047] - The metal content is a measure of the metal content, monitoring heavy metals such as mercury, lead, cadmium, copper and zinc is essential as they may be toxic to the environment and human health;

[0048] - The organic micropollutants monitors the presence of pesticides, solvents, medicaments, and other chemicals which can be harmful in low concentrations;

[0049] - Micro plastics content and / or nano plastics content may accumulate in nature hence it is positive to get an estimate of this kind of pollution,

[0050] - Pharmaceutical pollution may have a negative effect on any downstream digester or any downstream sewage treatment plant, or purification plant, or sewage work or the pharmaceutical pollution may pollute nature in general;

[0051] - The oil and grease content may cause problems in water treatment plants and contaminate aquatic environments; and / or

[0052] - The turbidity is measure of the clarity of rainwater, which may be affected by suspended particles and which is important for assessing the quality and need for further treatment.

[0053] In one embodiment, the bottom may comprise one or more sensor channels, wherein one or more sensors may be arranged within the one or more sensor channels. This provides an improved flow of water through or past the one or more sensors, because the water in the drainage hole is pushed into the sensor channels, thereby providing a better contact between the one or more sensors and the water for better and more reliable measurements of water quality parameters. The sensor channels, furthermore, protects the one or more sensor arranged in the one or more sensor channels from leaves, branches, trash, or any other waste matter in the drainage hole, which may damage the one or more sensors is the sensor were arranged exteriorly on the surface of the bottom.

[0054] The one or more sensors may comprise be a level-activated sensor, such as a level-activated conditioning meter, which is activated when the water level in the drainage hole reaches a pre-determined water level. The level-activated sensor can monitor on or more parameters such as water level, water flow, and water quality. The level-activated sensor may be activated via a mechanical reed switch ensuring that the sensor is only active at relevant water levels, thereby saving power and prolonging battery life, as the sensors only uses power when necessary.

[0055] The one or more sensors may further register how many times the water level in the drainage hole reaches and / or exceeds a pre-determined water level, e.g., by means of a RFID-chip. Thereby providing a simple and inexpensive way of monitoring the water level in the drainage hole. The one or more sensors may further measure the local flow in the sewer. By combining data from the flow measurement with the water level measurements, the overflow valve can provide detailed information on the operation of the sewer and any potential problems that need attending by a maintenance team.

[0056] In an embodiment, the overflow valve may further comprise a clogging indicator for monitoring whether the top of the elongated buoyant body is stuck under water. The clogging indicator comprises a first contact sensor for sensing connection with water, the first contact sensor may be positioned at a lower part of the elongated buoyant body i.e. on the part of the elongated buoyant body which will be in contact with water if the elongated buoyant body floats in water.

[0057] The clogging indicator may further comprise a second contact sensor for detecting contact with water, wherein the second contact sensor is on a top part of the elongated buoyant body i.e. on the part of the elongated buoyant member which will not be in contact with water if the elongated buoyant body floats in water if the drainage hole is not clogged or the elongated buoyant body is stuck in a lowermost position. Thus, if the elongated buoyancy member for some reason gets stuck while water levels are rising, then the clogging indicator will register water at the first and second contact sensor hence indicating that the elongated buoyant body is below water.

[0058] The clogging indicator may further comprise a third contact sensor configured to detect contact between the elongated buoyant member and an upper part of the overflow valve preferably the first stopping member. The third contact sensor may be positioned on the first stopping member,

[0059] If the first contact sensor detects contact with water, then the elongated buoyant member is in an open state, where water can flow into the drainage hole as the top of the elongated buoyant member and the hole is apart. If the first contact sensor detects water and the third contact sensor detects a contact between elongated buoyant member and an upper part of the overflow valve preferably the first stopping member, then the elongated buoyant member is in the blocked state and water cannot flow through the drainage hole.

[0060] If the first contact sensor does not detect water and the third contact sensor detects a contact between elongated buoyant member and an upper part of the overflow valve preferably the first stopping member, then the elongated buoyant member has been stuck and maintenance is required to unstuck the elongated buoyant member.

[0061] If the first contact sensor and the second contact sensor detect water, then the elongated buoyant member is stuck at a lower position and as a result water is very likely overflowing from the drainage hole or at least there is a great risk of overflowing. Hence service is required within a limit amount of time.

[0062] The clogging indicator may be adapted to send an alarm to a central control unit enabling a rapid response from a maintenance team. Thus, the condition of overflow valve does not require regularly manual inspections by a maintenance, thereby providing a more efficient monitoring of drainage hole and sewer conditions.

[0063] In another embodiment, the overflow valve may further comprise means for sending a signal to a central control unit in case the elongated buoyant member is stuck in the blocked state, such that a maintenance team may be sent to release the elongated buoyant member. The means for sending a signal may be a communication unit comprising at least one antenna for sending a wireless signal to central control unit, since the elongated buoyant member and the communication unit may be completely under water, then overflow valve may include a relay unit for relaying the wireless signal in order to assure longer range, wherein the relay unit is configured such that the antenna of the relay unit is above the water line to ensure longer range.

[0064] The means for sending a signal may be a communication unit comprising a wired connection to the central control unit.

[0065] The overflow valve according to the present invention may, thereby, combine several functions in one device, including preventing overflow from a drainage hole, precise real-time monitoring of the condition and / or water level of the drainage hole and sewer system, reliable operation, and flexible installation. The overflow valve, thus, improves the safety, efficiency and maintenance of sewer systems, especially during extreme weather conditions

[0066] In an aspect of the invention, the overflow valve further comprises a second stopping member, wherein the two or more gliding rods and the elongated buoyant member is arranged between the first stopping member and the second stopping member.

[0067] Thereby providing a base for the elongated buoyant member, which defines an end position for the open state, where the top and the hole are separated by a maximum distance. The elongated member is, thus, confined between of the first and second stopping member and the tow ore more gliding rods.

[0068] When the water level in the drainage hole decreases to a level below the second stopping member, the elongated buoyant member is stopped by the second stopping member and the bottom of the elongated buoyant member rests on the second stopping member. Thereby preventing the elongated buoyant member from traveling too far down the pipe or conduit of the drainage hole, which might carry the risk of the elongated buoyant member getting stock in and blocking the piping.

[0069] A further advantage of the second stopping member is that it provides locking frame which ensure the stability of the overflow valve.

[0070] In an aspect of the invention, the first stopping member comprises a first side facing a lid of the drainage hole and a second side facing the elongated buoyant member, wherein the second side comprises a sealing coating along a circumference of the hole.

[0071] Thereby ensuring a watertight and secure seal between the elongated buoyant member and the first stopping member in the blocked state such that water cannot penetrate the overflow valve in the blocked state from either above or below the overflow valve.

[0072] In an aspect of the invention, the sealing coating is rubber, natural rubber, an elastomer or a polymer with sealing properties.

[0073] Thereby providing a watertight and secure seal between the elongated buoyant member and the first stopping member.

[0074] In an aspect of the invention, the hole is substantially circular. This is advantageous as the hole the hole comprises not corners, where e.g., leaves, branches, trash, waste matter, and other sediments can get stuck and clock the overflow valve.

[0075] In an aspect of the invention, the overflow valve comprises two gliding rods, preferably three gliding rods, and more preferably four gliding rods, and / or wherein the elongated buoyant member comprises two tracks, preferably three tracks, and more preferably four tracks.

[0076] Thereby, the elongated buoyant member is trapped and held firmly between the two or more gliding rods. This further ensures a controlled and stable movement of the elongated buoyant member along the gliding rods.

[0077] In an aspect of the invention, the elongated buoyant element comprises two or more connectable modules.

[0078] Each connectable module may comprise a specific function such as one or more sensors for measuring water quality parameters, water level, and or valve clogging, which may require placement at different positions on the elongated buoyant member for optimal effect. Thereby, the elongated buoyant member can be assembled from two or more connectable modules which may have different function to provide an elongated buoyant member for a specific requirement matching the needs of draining hole in which the overflow valve is installed.

[0079] Furthermore, the connectable modules may be produced as standardised connectable modules, thus, by varying the number of connectable modules, the length of the elongated buoyant member may be changed. Thereby providing an elongated buoyant member with a length suitable for the dimensions of a specific drainage whole, to provide a more stable movement of the elongated buoyant member in the overflow valve.

[0080] In an embodiment, the elongated buoyant element may comprise an upper module configured for engaging the hole, a lower module, and one or more middle modules arranged between the upper module and the lower module, wherein the upper module, the lower module and the one or more middle modules are separate connectable modules. In a preferred embodiment, the elongated buoyant element may comprise an upper module configured for engaging the hole, a lower module, and a middle module. There may be two or more middle modules between the lower module and the upper module if it is required and each middle module may be designed for a specific purpose.

[0081] The upper module may comprise a communication unit including an antenna for wireless communication. Since the upper module is during normal use is the module closest to the top of the drainage hole then this will provide the best signal.

[0082] The different modules may be colour coded in accordance with their function such that a specific colour is associated with a specific function such as being carrier for a battery and / or computation unit and / or communication unit and / or specific sensors. A single module may have several colours or a specific pattern corresponding to a specific function or specific functions.

[0083] In an aspect of the invention, the at least one of the two or more connectable modules comprises a coating, wherein the coating is rubber, natural rubber, an elastomer, or a polymer.

[0084] Thereby providing the elongated buoyant member with a reduced surface friction, which prevents clogging materials, such as leaves, branches, trash, waste matter, and sediments, and other residues from getting stuck on the top of the elongated member and ensuring a reliable operation without the risk of clogging. Thereby, providing a selfcleaning overflow valve and ensuring a reliable operation without the risk of clogging.

[0085] The coating further ensures that the elongated buoyant member glides more smoothly along the two or more gliding rods due to the reduces surface friction.

[0086] Each connectable module may comprise one or more connection surfaces configured for facing and engaging a connection surface of another connectable module, wherein the one or more connection surfaces comprises a coating such as rubber, natural rubber, an elastomer, or a polymer. Thereby proving a watertight seal between two connected connectable modules. This is advantageous as the watertight seal may protect any electronics arranged in the connectable modules or within the connection e.g., electrical connections. In some embodiments, the connection surface may further comprise o-rings to provide a complete watertight connection seal between two connectable modules and protect any electrical connections.

[0087] In an embodiment, the upper module, the lower module, and / or the one or more middle modules comprises a coating, wherein the coating is rubber, natural rubber, an elastomer or a polymer.

[0088] In an aspect of the invention, the two or more connectable modules comprises a mechanical and / or and electrical connection configured for connecting the two or more connectable modules.

[0089] The mechanical connections may be a female lock connection and / or a male lock connection configured for receiving a female lock connection and / or a male lock connection on, respectively, on another connectable module. The male lock connection and the female lock connection may be configured for interlocking with each other by means of a rotation. Thereby providing a quick, easy, and simple mechanism for connecting two connectable modules.

[0090] The electrical connections enable an electrical contact between two connectable modules, such that for example a battery arranged in one connectable module may power a sensor arranged in another connectable module. The electrical contact may further be established through multiple connectable modules, thereby enabling electric communication between the several connectable modules. The electrical connection may, furthermore, also have character of a mechanical connection, thereby, the electrical connections may also function as a mechanical connection for connecting two or more connectable modules. Thus, in an embodiment, the electrical connection and the mechanical connection is the same connection.

[0091] In an embodiment, at least one connection surface of the two connection surfaces facing each other in an elongated buoyant member may comprise an o-ring for providing a complete watertight connection seal between two connectable modules, thereby protecting the electrical connections arranged within the connection between to connectable modules. In another embodiment, each connection surface of the connectable modules may comprise an o-ring, wherein the o-ring of one connection surface is displaced relative to o-ring of the connection surface of an adjacent connectable module. The two o-rings displaced relative to each other in connection between two adjacent connectable modules may, thereby, surround an electrical connection arranged between the two o-rings. Thus, an o-ring may be arranged on each side of an electrical connection, thereby providing a completely watertight connection seal between two connectable modules, which protects any electrical connections arranged within the connection between two connectable module.

[0092] In an aspect of the invention, one of the two or more connectable modules is an upper module configured for engaging the hole, wherein the upper module is made of an elastomer.

[0093] Thereby providing the upper module comprising top of the elongated buoyant member with an elasticity, which when pressed against the hole in the first stopping member in the blocked state provides a watertight seal between the elongated buoyant member and the first stopping member preventing water from inflow from and outflow to the surroundings from the drainage hole. The elasticity further prevents materials such as leaves, branches, trash, waste matter, and other sediments from disrupting the water seal, as the elasticity of the upper module may deform around such materials.

[0094] In some embodiment, the entire elongated buoyant member is made of an elastomer.

[0095] In another embodiment, the lower module and / or the one or more middle module may also be made of an elastomer.

[0096] In an aspect of the invention, the one of the two or more connectable modules comprises the top of the elongated buoyant member, wherein the top has oblique edges or a substantially spherical shape or a substantially cone shape or a shape complementary to the hole of the first stopping member.

[0097] Thereby preventing clogging of the overflow valve by e.g., leaves, branches, trash, waste matter, and other sediments, as the sloping surfaces of the top allows the clogging materials to automatically be removed from the top, as the clogging materials glide off the sloping surfaces. Thereby, providing a self-cleaning overflow valve and ensuring a reliable operation without the risk of clogging.

[0098] In an embodiment, the upper module comprises the top of the elongated buoyant member having oblique edges or a substantially spherical shape or a substantially cone shape or a shape complementary to the hole of the first stopping member. In an aspect of the invention, one of the two or more connectable modules is a lower module comprising the bottom of the elongated buoyant member, wherein the bottom comprises a sensor unit comprising one or more sensors for measuring water level and water quality such as pH-value, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), nutrients, total nitrogen (TN), Total phosphorus (TP), temperature, organic material, microbiological parameters, metal content, organic micropollutants, oil content, micro plastics, nano plastics, grease content, pharmaceutical pollution and / or turbidity.

[0099] By arranging the sensor unit in a lower module, the sensor unit is in contact with the water in the drainage hole, which is a requirement for the sensor unit to be able to measure the various different water quality parameters such as pH-value and temperature. The lower module may furthermore be partially or fully submerged in water, thereby the one or more sensors may be arranged partly or fully above and / or below the water depending on the parameter to be measured in the drainage hole, thereby enabling accurate measurement and data transmission.

[0100] In an embodiment, bottom of the lower module comprises one or more sensor channels, wherein the one or more sensors may be arranged withing the one or more sensor channels, thereby protecting the one or more sensors and providing better and more reliable measurements of water quality parameters.

[0101] The one or more sensors may be a level-activated sensor, such as a level-activated conditioning meter, which is activated when the water level in the drainage manhole reaches a pre-determined water level. The level-activated sensor can monitor one or more parameters such as water level, water flow, and water quality. The level-activated sensor may be activated via a mechanical reed switch ensuring that the sensor is only active at relevant water levels, thereby saving power and prolonging battery life, as the sensors only uses power when necessary.

[0102] In an aspect of the invention, at least one of the two or more connectable modules comprises one or more batteries for powering the sensor unit.

[0103] Thereby, multiple connectable modules comprising one or more batteries may be connected in the elongated buoyant member to provide the battery power needed for the sensor unit of a specific configuration of the elongated buoyant member. In an embodiment, the one or more middle modules may comprise one or more batteries for powering the sensor unit.

[0104] In an aspect of the invention, the overflow valve further comprises a friction element, the friction element clamps one of the two or more gliding rods between the elongated buoyant member and the first stopping member, wherein the friction member is displaced towards the first stopping member with an increasing water level.

[0105] The friction member may be displaced towards the first stopping member by the elongated buoyant member with an increasing water level. However, when the water level decreases the friction member maintains it position on the gliding rod and does not slide down the gliding rod along with the elongated buoyant member. Thereby, the friction member always manually indicates the highest registered water level in the drainage hole. This is advantageous, as it allows maintenance personal to quickly and precisely carry out inspections without the need of electronic equipment. After maintenance personal has inspected the drainage hole, they may release the friction member to reset it, thereby the friction member may again be displaced towards the first stopping member by the elongated buoyant member with an increasing water level to manually register a new highest water level in the drainage hole.

[0106] Another objective of the invention is achieved by a method for preventing water overflow from a drainage hole. The method comprises steps of:

[0107] - providing an overflow valve according to any one of claims 1 to 14 to the drainage hole; and

[0108] - sliding the elongated buoyant member between

[0109] - a blocked state, where the top of the elongated buoyant member engages the hole of the first stopping member with an increasing water level in the drainage hole, thereby preventing water overflow, and

[0110] - an open state, where the top disengages the hole with a decreasing water level in the drainage hole, thereby allowing water inflow.

[0111] Wherein the step of sliding is performed as a function of water level in the drainage hole.

[0112] All effect and advantageous described above for the overflow valve also applies for the method. The elongated buoyant member can, thereby, move between the open state, the blocked state and any intermediate states with a changing water level in the drainage hole.

[0113] When the water level in the drainage hole increases the elongated buoyant member slides towards the first stopping member, and when the water level in the drainage hole reaches a maximum, the elongated buoyant member is in the blocked state, where the top of the elongated buoyant member engages and blocks the hole in the first stopping member, thereby stopping water inflow to the drainage hole and preventing water overflow from the drainage hole. Thus, the overflow valve automatically closes off the drainage hole, as the water pressure from beneath the elongated buoyant member presses the top against the hole of the first stopping member, when the water level in the drainage hole reaches a critical level that may result in an overflow from the drainage hole.

[0114] When the water level in the drainage hole decreases the elongated buoyant member slides away from the first stopping member, moving the top of the elongated buoyant member away from the hole in the first stopping member, where the elongated buoyant member is in the open state, thereby allowing a water inflow to the drainage hole. Thus, when the water pressure from beneath the elongated buoyant member decreases, then the overflow valve automatically opens, and the drainage hole can again receive a water inflow.

[0115] Description of the Drawing

[0116] Various examples are described hereinafter with reference to the figures. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. It should also be noted that the figures are only intended to facilitate the description of the examples. They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. In addition, an illustrated example need not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

[0117] Exemplary embodiments of the invention are described in the figures, whereon:

[0118] Fig. 1 illustrates a side view of an overflow valve according to an embodiment of the present invention. Fig. 2 illustrates a top view of an overflow valve according to an embodiment of the present invention.

[0119] Fig. 3 illustrates a perspective view of an overflow valve according to an embodiment of the present invention.

[0120] Fig. 4 illustrates two different embodiments of an elongated buoyant member;

[0121] Fig. 5 illustrates a connection between two connectable modules; and

[0122] Fig. 6 illustrates an embodiment lower part of the elongated buoyancy member.

[0123] Detailed Description of the Invention

[0124] Exemplary examples will now be described more fully hereinafter with reference to the accompanying drawings. In this regard, the present examples may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the examples are merely described below, by referring to the figures, to explain aspects.

[0125] Throughout the specification, when an element is referred to as being “connected” to another element, the element is “directly connected” to the other element, “electrically connected”, “fluidic connected” or “communicatively connected” to the other element with one or more intervening elements interposed there between.

[0126] The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the terms “comprises" "comprising" "includes" and / or "including" when used in this specification specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0127] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the present specification. Figures 1-3 illustrates different views of an overflow valve 100 for a drainage hole (not shown) according to an embodiment of the present invention. The drainage hole may be a manhole, a utility hole, a maintenance hole, or any other sewer hole for sewer systems configured for carrying away water from enclosed volumes or surfaces. However, the drainage hole may also be a drainage hole for a house drain system, and any other drainage hole for a conduit system configured for carrying away water from enclosed volumes or surfaces.

[0128] The overflow valve 100 comprises an elongated buoyant member 10, which comprises a top 12, a bottom 14, and two or more tracks 16 arranged along the elongated buoyant member 10 between the top 12 and the bottom 14. The overflow valve 100 further comprises two or more gliding rods 20, configured for engaging the two or more tracks 16, wherein the elongated buoyant member 10 is slidable along the two or more gliding rods 20 with changing water level in the drainage hole.

[0129] The two or more tracks 16 of the elongated buoyant member 10 may be formed in the elongated buoyant member 10 as two or more indents, wherein the two or more gliding rods 20 are arranged in the two or more indents, thereby providing a larger contact surface between the elongated buoyant member 10 and the two or more gliding rods 20, which ensures a tighter grip between the elongated buoyant member 10 and the gliding rods 10. Thereby, the elongated buoyant member 10 is held firmly and stably between the two or more gliding rods 20.

[0130] In an embodiment, the overflow valve 100 may comprise two gliding rods 20, preferably three gliding rods 20, and more preferably four gliding rods 20, and / or the elongated buoyant member 10 may comprise two tracks 16, preferably three tracks 16, and more preferably four tracks 16. Thereby ensuring a controlled and stable movement of the elongated buoyant member 10 along the gliding rods 20, as the elongated buoyant member 10 is held more firmly and stably in the overflow valve 100 with and increasing number of gliding rods 20.

[0131] The overflow valve 100 furthermore comprises a first stopping member 30 configured for being connected to a frame of the drainage hole, where the first stopping member 20 comprises a hole 32. The two or more gliding rods 20 may be attached to the first stopping member 30, such that two or more gliding rods 20 provides a trajectory for the movement of the elongated buoyant member 10 in the drainage hole. Thereby controlling the trajectory of the elongated buoyant member 10 relative to the hole 32 of the first stopping member 30.

[0132] In an embodiment, the hole 32 may be substantially circular and / or the top 12 of elongated buoyant member 10 may have oblique edges or a substantially spherical shape or a substantially cone shape. Thereby, the top 12 may have a shape complementary to the shape of the hole 32. This prevents clogging of the overflow valve by e.g., leaves, branches, trash, waste matter, and other sediments, because the sloping surfaces of the top 12 allows the clogging materials to glide away from the top 12 along the sloping surfaces and the hole 32 does not comprise any corners where the clogging materials can get stock.

[0133] In the overflow valve 100, the elongated buoyant member 10 is slidable between two states:

[0134] - a blocked state, where the top 12 engages the hole 32 thereby preventing water overflow, and

[0135] - an open state, where the top 12 and the hole 32 are apart.

[0136] The elongated buoyant member 10 can, thus, move between the open state, the blocked state and any intermediate states with a changing water level in the drainage hole. When the water level in the drainage hole increases the elongated buoyant member 10 slides along the two or more gliding rods 20 towards the first stopping member 30, and when the water level in the drainage hole reaches a maximum, the elongated buoyant member 10 is in the blocked state, where the top 12 engages and blocks the hole 32, thereby stopping water inflow to the drainage hole and preventing water overflow from the drainage hole. When the water level in the drainage hole decreases the elongated buoyant member 10 slides along the two or more gliding rods 20 away from the first stopping member 30, moving the top 12 away from the hole 32, where the elongated buoyant member 10 is in the open state, thereby allowing a water inflow to the drainage hole.

[0137] The first stopping member 30 may comprise a first side 34 facing a lid of the drainage hole and a second side 36 facing the elongated buoyant member 10, wherein the second side 36 comprises a sealing coating 38 along a circumference of the hole 32. The sealing coating 38 may be rubber, natural rubber, an elastomer or a polymer with sealing properties. This ensures a watertight and secure seal between the elongated buoyant member 10 and the first stopping member 30 in the blocked state such that water cannot penetrate the overflow valve 100 in the blocked state from either above or below the overflow valve 100.

[0138] In another embodiment, the elongated buoyant member 10 may be made of an elastomer. The elasticity of the elongated buoyant member 10 may allow the elongated buoyant member 10 to deform around clogging materials caught in the hole 32 or on the elongated buoyant member 10 to ensure a watertight seal between the elongated buoyant member 10 and the first stopping member 30 in the blocked state.

[0139] In another embodiment, the elongated buoyant member 10 may comprise a coating providing the elongated buoyant member with a reduced surface friction, such as a rubber coating, natural rubber coating, an elastomer coating or a polymer coating. Thereby preventing clogging materials and other residues from getting stuck on the top 12 and ensuring that the elongated buoyant member 10 glides more smoothly along the two or more gliding rods 20.

[0140] The first stopping member 30 may further comprise mounting means for attaching the overflow valve 100 to a frame of the drainage hole. In some embodiments, the overflow valve 100 may have dimensions fitting the standard dimensions of public drainage holes to enable installation in existing sewer systems.

[0141] In an embodiment, the bottom 14 of the elongated buoyant member 10 may have oblique edges or a substantially spherical shape or a substantially cone shape or a shape similar to the shape of the top 12. Thereby, the bottom 14 may always be under water.

[0142] The bottom 14 may further comprise a sensor unit comprising one or more sensors for measuring water level and / or water quality such as pH-value, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), total nitrogen (TN), Total phosphorus (TP), temperature, microbiological parameters, metal content, organic micropollutants, oil content, grease content, and / or turbidity. The one or more sensors may be level-activated sensors, such as a level-activated conditioning meter, which is activated when the water level in the drainage hole reaches a pre-determined water level. The level-activated sensors may be activated via a mechanical reed switch ensuring that the sensor is only active at relevant water levels, thereby saving power and prolonging battery life. The one or more sensors may further register how many times the water level in the drainage hole reaches and / or exceeds a pre-determined water level, e.g., by means of a RFID-chip. The one or more sensors may further measure the local flow in the sewer.

[0143] In and embodiment, the bottom 14 may comprise one or more sensor channels 70, wherein one or more sensors are arranged within the one or more sensor channels 70, this is illustrated in figure 6. This provides an improved flow of water through or past the one or more sensors, because the water in the drainage hole is pushed into the sensor channels 70, thereby providing a better contact between the one or more sensors and the water for better and more reliable measurements of water quality parameters. The sensor channels 70, furthermore protects the one or more sensor arranged in the one or more sensor channels from leaves, branches, trash, or any other waste matter in the drainage hole, which may damage the one or more sensors.

[0144] In another embodiment, the overflow valve 100 may comprise means for sending a signal to a central control unit in case the elongated buoyant member 10 is stuck in the blocked state, such that a maintenance team may be sent to release the elongated buoyant member 10.

[0145] The elongated buoyant element 10 may further have a positive buoyancy in water. Preferable the elongated buoyant member 10 has a buoyancy in water that allows approximately , 14, 1 , or between and 14 of the elongated buoyant member to be submerged in water. In a preferred embodiment, the elongated buoyant member has buoyancy in water that allows approximately 14 of the elongated buoyant member to be submerged in water. This enables that a sensor unit arranged in the bottom 14 to be in contact with the water, which is a requirement for the sensor unit to be able to measure the various different water quality parameters such as pH-value and temperature.

[0146] The overflow valve 100 may further comprise a second stopping member 40, wherein the two or more gliding rods 20 and the elongated buoyant member 10 is arranged between the first stopping member 30 and the second stopping member 40. The second stopping member 40, then act as a base for the elongated buoyant member 10, which defines an end position for the open state, where the top 12 and the hole 32 are separated by a maximum distance. The elongated buoyant member 10 is, thus, confined between of the first stopping member 30 and second stopping member 40 and the tow ore more gliding rods 20. The overflow valve 100 may furthermore comprise a friction element, the friction element clamps one of the two or more gliding rods 20 between the elongated buoyant member 10 and the first stopping member 30. The friction member is then displaced towards the first stopping member 30 with an increasing water level, and when the water level decreases again the friction member maintains its position on the gliding rod 20 and does not slide back down the gliding rod along 20 with the elongated buoyant member 10. Thereby, the friction member always manually indicates the highest registered water level in the drainage hole.

[0147] Two different embodiments of an elongated buoyant member 10 is illustrated in figure 4A and 4B. Both embodiments of the elongated buoyant member 10 illustrates an elongated buoyant member 10 comprising two or more connectable modules 50, where each connectable module 50 may comprise a specific function, such as comprising one or more sensors for measuring water quality parameters, water level, and / or valve clogging. Measurement of these parameter may require the one or more sensors to be arranged at different positions on the elongated buoyant member 10 for optimal effect.

[0148] The elongated buoyant member 10 can, thus, be assembled from two or more connectable modules 50 which may have different functions to provide an elongated buoyant member 10 suitable for a specific purpose which matches the needs of draining hole in which the overflow valve 100 is installed.

[0149] Furthermore, by varying the number of connectable modules 50, the length of the elongated buoyant member may be changed 10.

[0150] In an embodiment, the elongated buoyant element 10 may comprise an upper module 52 configured for engaging the hole 32, a lower module 56, and one or more middle modules 54 arranged between the upper module 52 and the lower module 56.

[0151] In an embodiment, at least one of the two or more connectable modules 50 may comprise a coating, wherein the coating is rubber, natural rubber, an elastomer or a polymer. Thereby providing the elongated buoyant member 10 with a reduced surface friction.

[0152] The two or more connectable modules 50 may further comprises a mechanical connection 64 and / or and electrical connection 62 configured for connecting the two or more connectable modules 50. The mechanical connection 64 may be a female lock connection 66 and / or a male lock connection 66 configured for receiving a female lock connection 66 and / or a male lock connection 68, respectively, on another connectable module. The male lock connection 66 and the female lock 68 connection may be configured for interlocking with each other by means of a rotation.

[0153] The electrical connections 62 enable an electrical contact between two connectable modules 50, such that for example a battery arranged in one connectable module 50 may power a sensor arranged in another connectable module 50. The electrical contact may further be established through multiple connectable modules 50, thereby enabling electric communication between the several connectable modules 50. The electrical connection 62 may, furthermore, also have character of a mechanical connection 64. thereby, the electrical connections 62 may also function as a mechanical connection 64 for connecting two or more connectable modules 50. Thus, in an embodiment, the electrical connection 62 and the mechanical connection 64 is the same connection.

[0154] In an embodiment, each connectable module 50 may comprise one or more connection surfaces 58 configured for facing and engaging a connection surface 58 of another connectable module 58, wherein the one or more connection surfaces 58 may comprise a coating such as rubber, natural rubber, an elastomer, or a polymer. Thereby proving a watertight seal between two connected connectable modules 50 protecting any electronics arranged in the connectable modules 50 or any electrical connections 62 between to connectable modules 50.

[0155] Figure 5 illustrates an embodiment of a connection between two connectable modules 50, wherein, the connection surfaces 58 further comprises o-rings 60 to provide a complete watertight connection seal between two connectable modules 50. At least one connection surface 58 of the two connection surfaces 58 facing each other in an elongated buoyant member 10 may comprise an o-ring 60. In an embodiment, each connection surface 58 of a connectable module 50 may comprise an o-ring 60, wherein the o-ring 60 of one connection surface 58 is displaced relative to o-ring 60 of the connection surface 58 of an adjacent connectable module 50. The two o-rings 60 displaced relative to each other in connection between two adjacent connectable modules 50 may, thereby, surround an electrical connection 62 arranged between the two o-rings 60. Thus, an o-ring 60 may be arranged on each side of an electrical connection 62, thereby providing a completely watertight connection seal between two connectable modules 50, which protects any electrical connections arranged within the connection between two connectable modules 50.

[0156] The upper module 52 may be configured for engaging the hole 32, wherein the upper module 52 is made of an elastomer to allows the upper module 52 to deform around any clogging material and provide a watertight seal with the first stopping member 30 in the blocked state.

[0157] In an embodiment, the lower module 56 and / or the one or more middle module 52 may also be made of an elastomer.

[0158] The upper module 52 may comprise the top 12 of the elongated buoyant member 10, and the top 12 may have oblique edges or a substantially spherical shape or a substantially cone shape or a shape complementary to the hole 32 of the first stopping member 30. Figure 4A and 4B illustrates upper modules 52 with different shapes of the top 12 of the elongated buoyant member 10.

[0159] The lower module 56 may comprise the bottom 14 of the elongated buoyant member 10, wherein the bottom 14 comprises a sensor unit comprising one or more sensors for measuring water level and water quality such as pH-value, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), total nitrogen (TN), Total phosphorus (TP), temperature, microbiological parameters, metal content, organic micropollutants, oil content, grease content, and / or turbidity. By arranging the sensor unit in a lower module 56, the sensor unit is in contact with the water in the drainage hole, which is required for the sensor unit to be able to measure the various different water quality parameters such as pH-value and temperature.

[0160] In an embodiment, bottom 14 of the lower module 56 comprises one or more sensor channels 70, wherein the one or more sensors may be arranged withing the one or more sensor channels 70. This is illustrated in figure 6.

[0161] At least one of the two or more connectable modules 50 may comprise one or more batteries for powering the sensor unit. Thereby, multiple connectable modules 50 comprising one or more batteries may be connected in the elongated buoyant member 10 to provide the battery power needed for the sensor unit. In an embodiment, the one or more middle modules may comprise the one or more batteries.

[0162]

Claims

CLAIMS1. An overflow valve (100) for a drainage hole, the overflow valve (100) comprising - an elongated buoyant member (10) comprising a top (12), a bottom (14), and two or more tracks (16) arranged along the elongated buoyant member (10) between the top (12) and the bottom (14); wherein the elongated buoyant element (10) has a positive buoyancy in water,- two or more gliding rods (20) configured for engaging the two or more tracks (16);- a first stopping member (30) configured for being connected to a frame of the drainage hole, the first stopping member (30) comprising a hole (32); wherein the elongated buoyant member (10) is slidable along the two or more gliding rods (20) with changing water level, the elongated buoyant member (10) being slidable between two states:- a blocked state, where the top (12) engages the hole (32) thereby preventing water overflow, and- an open state, where the top (12) and the hole (32) are apart.

2. An overflow valve (100) according to claim 1 , wherein the overflow valve (10) further comprises a second stopping member (40), wherein the two or more gliding rods (20) and the elongated buoyant member (10) is arranged between the first stopping member (30) and the second stopping member (40).

3. An overflow valve (100) according to claims 1 or 2, wherein the first stopping member (30) comprises a first side (34) facing a lid of the drainage hole and a second side (36) facing the elongated buoyant member (10), wherein the second side (36) comprises a sealing coating (38) along a circumference of the hole (32).

4. An overflow valve (100) according to claim 3, wherein the sealing coating (38) is rubber, natural rubber, an elastomer or a polymer with sealing properties.

5. An overflow valve (100) according to any one of the preceding claims, wherein the hole (32) is substantially circular.

6. An overflow valve (100) according to any one of the preceding claims, wherein the overflow valve (100) comprises two gliding rods (20), preferably three gliding rods (20), and more preferably four gliding rods (20), and / or wherein the elongated buoyantmember (10) comprises two tracks (16), preferably three tracks (16), and more preferably four tracks (16).

7. An overflow valve (100) according to any one of the preceding claims, wherein the elongated buoyant element (10) comprises two or more connectable modules (50).

8. An overflow valve (100) according claim 7, wherein at least one of the two or more connectable modules (50) comprises a coating, wherein the coating is rubber, natural rubber, an elastomer or a polymer.

9. An overflow valve (100) according claims 7 or 7, wherein the two or more connectable modules (50) comprises a mechanical and / or and electrical connection configured for connecting the two or more connectable modules (50).

10. An overflow valve (100) according to any one of claims 7 to 9, wherein one of the two or more connectable modules (50) is an upper module (52) configured for engaging the hole (32), wherein the upper module (52) is made of an elastomer.

11. An overflow valve (100) according to any one of claims 7 to 10, wherein one of the two or more connectable modules (50) comprises the top (12) of the elongated buoyant member (10), wherein the top (12) has oblique edges or a substantially spherical shape or a substantially cone shape or a shape complementary to the hole (32) of the first stopping member (30).

12. An overflow valve (100) according to any one of claims 7 to 11 , wherein one of the two or more connectable modules (50) is a lower module (56) comprising the bottom (14) of the elongated buoyant member (10), wherein the bottom (14) comprises a sensor unit comprising one or more sensors for measuring water level and water quality such as pH-value, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), nutrients, total nitrogen (TN), Total phosphorus (TP), temperature, organic material, microbiological parameters, metal content, organic micropollutants, oil content, micro plastics, nano plastics, grease content, pharmaceutical pollution and / or turbidity.

13. An overflow valve (100) according to claim 12, wherein at least one of the two or more connectable modules (50) comprises one or more batteries for powering the sensor unit.

14. An overflow valve (100) according to any one of the preceding claims, wherein the overflow valve (100) further comprises a friction element, the friction element clamps one of the two or more gliding rods (20) between the elongated buoyant member (10) and the first stopping member (30), wherein the friction member is displaced towards the first stopping member (30) with an increasing water level.

14. A method for preventing water overflow from a drainage hole, the method comprises steps of:- providing an overflow valve (100) according to any one of claims 1 to 13 to the drainage hole; and- sliding the elongated buoyant member (10) between- a blocked state, where the top (12) of the elongated buoyant member (10) engages the hole (32) of the first stopping member (30) with an increasing water level in the drainage hole, thereby preventing water overflow, and - an open state, where the top (12) disengages the hole (32) with a decreasing water level in the drainage hole, thereby allowing water inflow.

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