Sanitary flushing system and method of flushing a pipe of the sanitary flushing system

Abstract

The invention relates to a sanitary flushing system comprising a water line (1) in which water is guided in a flow direction (F), a flushing fitting (4) which can be actuated to flush the water line (1), a control unit (5) for actuating the flushing fitting (4), a first temperature sensor (6) for measuring a first water temperature (T1), and a second temperature sensor (7) for measuring a second water temperature (T2), wherein the measurement values of the measured temperatures can be transmitted from the temperature sensors (6, 7) to the control unit (5), wherein, during a flushing process during which the flushing fitting is open such that the water line (1) is flushed, a temperature difference (dT) between the first water temperature (T1) and the second water temperature (T2) can be determined by the control unit (5), and wherein the flushing fitting (4) is closed when the temperature difference (dT) reaches a threshold value (dTS).

Description

[0001] The present invention relates to a hygienic flushing system according to the preamble of claim 1 and a method for a hygienic flushing system according to claim 10. STATE OF THE ART

[0002] If water pipes are not used for an extended period, such as several days or weeks, the water can become contaminated due to physical, chemical, and biological processes. This contamination problem is particularly prevalent in buildings that are unoccupied for long periods. During this time, the water stagnates in the pipes. This can occur, for example, in schools, universities, hotels, barracks, stadiums, and similar facilities. However, the problem also arises in single-family and multi-family homes.

[0003] Water contamination due to stagnation can be prevented by regularly flushing the water supply system with a so-called hygienic flush. Flushing systems that perform hygienic flushing automatically or semi-automatically are known from the prior art.

[0004] A key objective of hygienic flushing systems is to replace all the water, meaning the entire pipe volume, during a single flush. With current systems, the practice of running the flush for a longer time as a precaution has led to unnecessary water loss.

[0005] EP 2 500 475 proposes a temperature-controlled flushing process, whereby the flushing continues until a substantially constant water temperature is measured. The problem with this method is that the criterion of a constant water temperature is highly unreliable for determining the exchange of the pipe contents due to temperature fluctuations in the fresh water. Therefore, the method according to EP 2 500 475 results in an unreliable flushing process. Another hygienic flushing system is disclosed in DE 10 2019 201 263A1. PRESENTATION OF THE INVENTION

[0006] Based on this prior art, the invention is based on the objective of providing a hygienic flushing system that overcomes the disadvantages of the prior art. In particular, a preferred objective of the present invention is to provide a hygienic flushing system with which it can be more easily determined whether the entire volume of a pipeline to be flushed has been flushed.

[0007] This problem is solved by the subject matter of claim 1. Accordingly, a hygienic flushing system comprises a water pipe in which water flows in one direction, a flushing valve that can be controlled to flush the water pipe, a control unit for controlling the flushing valve, a first temperature sensor for measuring a first water temperature T1, and a second temperature sensor for measuring a second water temperature T2. The second temperature sensor is arranged downstream of the first temperature sensor in the direction of water flow. The measured temperatures can be transmitted from the temperature sensors to the control unit. During a flushing process in which the flushing valve is open so that the water pipe is flushed, a temperature difference dT between the first water temperature T1 and the second water temperature T2 is determined by the control unit.The flushing valve closes when the temperature difference dT reaches a threshold value dTS.

[0008] In other words, the temperature difference dT must equal the threshold value dTS for the flushing process to be completed. This criterion allows for the creation of a simple and reliable flushing system. Temperature measurement confirms that the temperature, or water temperature, has equalized between the two measuring points in the pipeline, indicating a complete exchange of the flushing water.

[0009] Monitoring the water temperature also offers the advantage that a well-functioning flushing system can be provided using cost-effective components. In particular, the use of expensive sensors, such as flow sensors, etc., is eliminated.

[0010] A further advantage is that the measured temperatures can also be used for other purposes, such as assessing water quality.

[0011] A further advantage is that existing buildings can be easily retrofitted with a hygienic flushing system according to the invention. Furthermore, by measuring the temperature differential, it is not necessary to know the exact volume or length of the piping, which means that the system can be easily retrofitted even in existing buildings where the pipe layout is usually unknown.

[0012] The temperature difference dT between the first temperature T1 and the second temperature T2 is expressed mathematically as follows: dT = T 1 − T 2

[0013] The two temperatures T1 and T2 are preferably measured continuously during a rinsing process. The measurement of both temperatures is preferably performed simultaneously. Furthermore, the temperature difference dT during a rinsing process is also preferably calculated continuously. The comparison between the temperature difference dT and the threshold value dTS is also performed continuously.

[0014] Alternatively, it is also conceivable that the measurement of the two temperatures T1 and T2, the calculation of the temperature difference dT, and the comparison between the temperature difference dT and the threshold value dTS are performed periodically at predetermined time intervals. These time intervals can be a few seconds.

[0015] The choice of threshold value essentially determines the duration of the flushing process. With a low threshold, the first temperature is very close to the second, meaning the water in the pipe is essentially the same temperature, so it can be assumed with a high degree of certainty that the pipe has been completely flushed. With a high threshold, the temperature difference between the first and second temperatures is greater, and it can no longer be said with absolute certainty that the pipe has been completely flushed. The choice of threshold value is crucial for the degree of flushing of the pipe. An optimal threshold value has the advantage that the pipe is completely flushed and that not too much fresh water is wasted. The threshold value depends primarily on the boundary conditions regarding temperatures.In particular, the threshold value depends on the temperature difference between the ambient temperature and the water temperature. For a cold water pipe and a room temperature of 22°C, the threshold value can be in the range of 0 to 10 Kelvin, especially 0 to 5 Kelvin. However, for a hot water pipe, the threshold value can also be higher than 10 Kelvin.

[0016] During stagnation, the temperature in the water pipe eventually reaches the ambient temperature, depending on the pipe's installation method and design. Typically, during this stagnation, the second temperature, T2, is essentially the ambient temperature.

[0017] Before the flushing process, the flushing valve is closed. To initiate the flushing process, the flushing valve is opened, and the water already in the water pipe flows out through the flushing valve, while fresh water flows into the water pipe through the inlet.

[0018] Preferably, the threshold value dTS is calculated during the flushing process as a function of the measured first temperature T1 and / or as a function of the measured second temperature T2 at the start of the flushing process. The phrase "at the start of the flushing process" means that the second temperature T2 is measured at the moment the flushing valve is opened; or that the temperature T2 is measured within a narrow time window of a maximum of 20 seconds after the flushing valve is opened. However, this time window can also be shorter, for example, a maximum of 15 seconds or a maximum of 10 seconds. The second temperature, measured at the start of the flushing process and then used to calculate the threshold value dTS, is designated as T2_t0.

[0019] This calculation allows the threshold to be set based on the actual temperature conditions, providing a very accurate system with regard to the flushing volume.

[0020] The threshold value dTS is calculated continuously or at fixed intervals by the control unit during the rinsing process. Continuous calculation means that the threshold value is determined continuously. Calculation at fixed intervals means that the threshold value is calculated periodically, for example, at intervals of 5 seconds between each calculation. The calculated threshold value dTS is used for the comparison between the temperature difference and the threshold value described above. The comparison between the temperature difference dT and the threshold value dTS can also be performed continuously or at fixed intervals.

[0021] In a first embodiment claimed in claim 1, the threshold value dTS is formed as the difference between the first water temperature T1 and the second water temperature T2_t0 at the start of the rinsing process and by multiplying the difference value by a quotient Q. Expressed in a mathematical formula, this means: dTS = T 1 − T 2 _t 0 * Q

[0022] The quotient can be set to 0.25, for example. Using a cold water pipe as an example, the first temperature T1 = 12°C and the second temperature is initially equal to the ambient temperature, for example T2_t0 = 25°C. This results in a difference value as follows: T 1 − T 2 _t 0 = 12 ° − 25 ° = − 13 ° .

[0023] The threshold value dTS then results as follows: TS = T 1 − T 2 _t 0 * Q = 12 ° − 25 ° * 0.25 = − 3.25 ° .

[0024] Consequently, the rinsing process lasts until the temperature difference between the first temperature T1 and the second temperature T2 reaches the threshold value dTS = -3.25°.

[0025] The use of the quotient Q is particularly advantageous because a threshold value can be determined at which optimal flushing with respect to the volume flushed out is achieved. This means that optimal volume flushing is achieved, where the required volume is flushed out without wasting too much water.

[0026] The choice of the value of the quotient Q depends primarily on the characteristics of the pipe system, particularly its length and diameter, as well as the pipe material and wall thickness. Due to the flow profile of the water in the pipe, approximately twice the pipe volume must be exchanged to replace all the water in turbulent flow conditions, which can also influence the quotient Q. The lower the quotient Q, the greater the exchange volume, and vice versa.

[0027] Preferably, the quotient Q is greater than 0. In particular, the quotient Q is between 0.1 and 1, especially between 0.15 and 0.5, and most preferably 0.25. These ranges have proven advantageous for typical diameters in the range of 15 to 40 millimeters and pipe lengths in the range of 10 to 50 meters.

[0028] In a second embodiment claimed in claim 1, instead of the second water temperature T2_t0 at the start of the rinsing process, an ambient temperature measured by a further temperature sensor is used. The ambient temperature is represented by the variable T3. In this case, the threshold value dTS is calculated using the quotient as follows: dTS = T 1 − T 3 * Q

[0029] During a flushing process, the first temperature drops very quickly because fresh water flows into the pipe. The second temperature drops slowly because the water already in the pipe, which is warmer than the fresh water, flows through it.

[0030] Preferably, the first temperature sensor is arranged in the area of ​​a pipe inlet of the water pipe.

[0031] Preferably, the hygienic flushing system further comprises at least one dispensing fitting connected to the water line, with which a dispensing process can be carried out to draw water from the water line. A dispensing fitting could be, for example, a toilet cistern, a faucet, a shut-off valve, or a shower. Other sanitary fittings are also conceivable. The at least one dispensing fitting can be located at a line outlet, i.e., where the flushing fitting is advantageously located. It would also be conceivable to locate the at least one dispensing fitting somewhere between the line inlet and outlet.

[0032] In one variant, the dispensing tap and the rinsing tap can be provided by a single tap.

[0033] In one variant, the second temperature sensor is preferably located near the tap. If multiple taps are installed, the second temperature sensor is preferably located near the tap that is furthest downstream of the water line. The phrase "near the tap" means that the second temperature sensor is located either directly at the tap or at a distance of no more than 3 meters along the water line from the tap.

[0034] In another variant, the second temperature sensor is preferably located near the flushing tap. The phrase "near the flushing tap" means that the second temperature sensor is located directly at the flushing tap or at a distance of no more than 3 meters along the water pipe from the flushing tap.

[0035] The triggering of the rinsing process is preferably characterized by, that a rinsing process is triggered if the second temperature T2 remains essentially constant for a predetermined period of time, and / or that a rinsing process is triggered if the second temperature T2 exceeds a limit value, and / or that a rinsing process is triggered after a predetermined period of time has elapsed since the last rinsing process.

[0036] The predetermined duration is preferably greater than 48 hours or greater than 72 hours.

[0037] The limit for the second temperature is in the range of 20°C to 30°C for cold water pipes, particularly at 25°C. The limit for the second temperature is in the range of 45°C to 60°C for hot water pipes, particularly at 50°C.

[0038] Preferably, the control unit further comprises a timing element that records the time elapsed after a rinsing process. During a dispensing operation, it is determined whether the aforementioned threshold value is reached, and upon reaching the threshold value, the elapsed time is reset to zero and the process restarts. Another rinsing process is triggered after a predetermined time period has elapsed since the zero value. This time period can be selected according to the aforementioned time period.

[0039] This has the advantage that if a complete exchange of the rinsing water is achieved during a dispensing process, the time for a time-controlled rinsing process can start again from the beginning.

[0040] Preferably, the temperature sensors are connected wirelessly or via a wired connection to the control unit for transmitting the measured temperatures. The measured temperatures are transmitted as analog or digital signals.

[0041] Preferably, the flushing fitting has an electrically controllable valve element, wherein the valve element can be controlled by the control unit such that the valve element opens at the start of a flushing process and closes at the end of the flushing process. The valve element is preferably wirelessly or via a wired connection to the control unit for transmitting a control command. The control command for closing the flushing fitting is given when the temperature difference dT has reached the aforementioned threshold value dTS.

[0042] Preferably, the temperature sensors for measuring the water temperature are arranged such that the water temperature can be measured directly or indirectly. In an indirect measurement, the temperature of the outside of the pipe is recorded, which allows a conclusion to be drawn about the water temperature. In a direct measurement, the temperature sensors protrude into the pipe and are in direct contact with the water.

[0043] The temperature sensor for measuring the ambient temperature is preferably arranged in an area of ​​a room through whose walls the water pipe extends or into which the water pipe empties.

[0044] Preferably, the temperature sensor is a PT1000 element or an NTC element.

[0045] A procedure for flushing a water line of a hygienic flushing system according to the above description includes the following steps: Initiating a flushing process by opening the flushing valve so that the water line is flushed, determining a temperature difference dT between the first water temperature and the second water temperature by the control unit during the flushing process, and closing the flushing valve when the temperature difference dT reaches a threshold value dTS according to claim 10.

[0046] Further embodiments are specified in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Preferred embodiments of the invention are described below with reference to the drawings, which serve only for illustration and are not to be interpreted restrictively. The drawings show: Fig. 1 is a schematic view of a hygienic flushing system according to an embodiment of the present invention; and Fig. 2 is a schematic representation of temperature profiles during a flushing process of the hygienic flushing system according to Figure 1. DESCRIPTION OF PREFERRED EXECUTION FORMS

[0048] In the Figure 1 A hygienic flushing system is schematically depicted. In the embodiment shown, the hygienic flushing system comprises a water pipe 1 in which water is guided in a flow direction F, a flushing fitting 4 for flushing the water pipe 1, a control unit 5 for controlling the flushing fitting 4, a first temperature sensor 6 for measuring a first water temperature T1, and a second temperature sensor 7 for measuring a second water temperature T2.

[0049] Water pipe 1 has an inlet 2, an outlet 3 with a flushing valve 4, and another outlet 3 with a tap 9. Fresh water flows into water pipe 1 via inlet 2. During a flushing cycle, the flushing valve 4 is activated by the control unit 5, opening the valve so that water can flow out of water pipe 1 via outlet 3. Fresh water then flows in via inlet 2, thus replacing the water in water pipe 1.

[0050] Additional taps may be connected to water line 1. These additional taps may be located anywhere between line inlet 2 and line outlet 3, or directly at line outlet 3.

[0051] The two temperature sensors 6 and 7 are spaced apart. Depending on the installation, the distance is several meters or even several dozen meters. The first temperature sensor 6 is located upstream of the second temperature sensor 7 in the direction of flow F. During a flushing process, the fresh water therefore first passes the first temperature sensor 6 and then the second temperature sensor 7. The first temperature sensor 6 detects a first water temperature T1, and the second temperature sensor 7 detects a second water temperature T2. Typically, the second temperature sensor 7 is located near the tap 9 or the flushing tap 4.

[0052] The temperature values ​​measured by temperature sensors 6 and 7 are transmitted by these two sensors to the control unit 5, which then processes the temperature values ​​T1 and T2 as described below. For this purpose, temperature sensors 6 and 7 provide control signals that can be received by the control unit 5.

[0053] In the Figure 2 Typical temperature profiles are shown. The x-axis represents time t in seconds and the y-axis represents temperature in °C.

[0054] The upper representation according to the Figure 2This shows the temperature profile of the first temperature T1 and the second temperature T2 during a water draw. Typically, a water pipe maintains a constant temperature when no water is being drawn. In this case, the first temperature T1 and the second temperature T2 are initially in equilibrium at approximately 25°C. In practice, this means that without water being drawn, the two temperatures T1 and T2 typically correspond to the ambient temperature. However, depending on the application, the first temperature T1 can also differ from the ambient temperature. When a flushing cycle begins, the first temperature T1 drops very quickly because fresh water flows into the pipe. After a certain period, the first temperature T1 remains essentially constant, at approximately 12°C in this example. In contrast, the second temperature T2 decreases more slowly.

[0055] During a flushing process in which water line 1 is flushed, a temperature difference dT between the first water temperature T1 and the second water temperature T2 is determined by the control unit 5. The flushing valve 4 is then closed when the temperature difference dT reaches a threshold value dTS. This is shown in the lower diagram of the Figure 2 The threshold value dTS is shown here according to a particularly preferred embodiment, which is described below. The curve dT shows the difference between the temperature T1 and the temperature T2 over time t. As soon as the curve dT reaches the threshold value dTS, the flushing process is interrupted by closing the flushing valve 4. This is shown in the illustration of the Figure 2 This is the case when the trend curve dT intersects the threshold curve dTS. The point of intersection is denoted by the reference symbol S.

[0056] The threshold value dTS is determined during the flushing process, depending on the measured first temperature T1 and / or the measured second temperature T2 at the start of the flushing cycle. At the start of the flushing cycle, the second temperature T2 is measured and recorded as T2_t0. T2_t0 represents the second water temperature at the time the flushing cycle begins. Typically, T2_t0 is stored in the control unit. The temperature T2_t0 measured at the start of the flushing cycle is used as a constant in the calculation formula during the continuous determination of the threshold value dTS.

[0057] The phrase "at the start of the rinsing process" is preferably to be understood as meaning that the second temperature is measured when the rinsing tap is opened, or immediately afterwards, or a few seconds thereafter.

[0058] In a second embodiment, it would also be possible to measure the ambient temperature with another sensor and to use the ambient temperature T3 instead of T2_t0 in the calculations. The threshold value dTS is then calculated as the difference between the first temperature T1 and the ambient temperature T3: dTS = (T1 - T3)*Q.

[0059] In the Figure 2 The effective discharge volume EA and the target discharge volume SA are shown. At the intersection point S of the two lines A and S, the effective discharge volume EA equals the target discharge volume SA.

[0060] In the illustrated embodiment, the threshold value dTS is calculated as the difference between the first water temperature T1 and the second water temperature T2_t0, i.e., the second water temperature at the start of the rinsing process, and is determined by multiplying this difference value by a quotient Q. In this example, the second water temperature T2 is measured immediately at or after the start of the rinsing process to determine the threshold value. Figure 2 The temperature is set at time t=0 seconds and defined as T2_t0. In this example, the first water temperature T1 is measured throughout the entire rinsing process. Expressed mathematically, this means that the threshold value dTS is determined as follows: dTS = T 1 − T 2 _t 0 * Q = 12 − 25 * Q

[0061] The quotient Q is typically greater than 0. A preferred quotient, according to the example, is 0.25. This results in the following numerical example: At different times after the start of the rinsing process, the threshold value dTS, according to the example, is as follows: Figure 2 The following are numerical examples: Time 0 seconds: dTS = ( T1 - T2_t0 ) * Q = (25 - 25) * 0.25 = 0K Time 10 seconds: dTS = ( T1 - T2_t0) * Q = ( 14 - 25) * 0.25 = -2.75 K Time 20 seconds: dTS = (T1 - T2_t0) * Q = (13 - 25) * 0.25 = -3K Time 60 seconds: dTS = ( T1 - T2_t0 ) * Q = ( 12 - 25 ) * 0.25 = -3.25 K

[0062] During each flushing cycle, the temperature T1 typically reaches an equilibrium because the incoming fresh water usually has a constant temperature. This also causes the threshold value dTS to assume a constant value after a certain time. In the example shown, the initial temperature T1 reaches a constant value approximately 40 to 60 seconds after the start of the flushing cycle. Since, according to the example, the initial temperature T1 assumes a constant value, the calculated threshold value dTS also becomes constant. According to the example, the threshold value dTS is -3.25 K after 40 to 60 seconds from the start of the flushing cycle, and the flushing cycle ends as soon as the measured temperature difference between T1 and T2 reaches -3.25 K.

[0063] The threshold value dTS is preferably calculated continuously throughout the entire rinsing process, or at predetermined intervals of a few seconds. This ensures that temperature changes in the initial temperature can be taken into account.

[0064] The calculation could also be done in reverse, which can be expressed in formulas as follows: dT = T2 - T1 and dTS = (T2_t0 - T1) * Q.

[0065] According to the second embodiment described above, the mathematical formulas for calculating the temperature difference dT and for calculating the threshold value dTS can be formulated as follows: dT = T 1 − T 2 dTS = T 1 − T 3 * Q

[0066] Accordingly, for the calculation of the threshold value dTS according to the first embodiment, the temperature T2_t0 measured at the start of the rinsing process or the ambient temperature T3 can be used.

[0067] Several options are available for triggering the rinsing process, namely that a rinsing process is triggered if the second temperature T2 remains essentially constant for a predetermined period of time and / or that a rinsing process is triggered if the second temperature T2 exceeds a limit value and / or that a rinsing process is triggered after a predetermined period of time has elapsed since the last rinsing process.

[0068] In a particularly preferred embodiment, the control unit 5 further comprises a timer. After a flushing process, the timer records the elapsed time. During a dispensing operation, it determines whether the threshold value dTS is reached. Upon reaching the threshold value dTS, the elapsed time is reset to zero and the process restarts. A further flushing process is then triggered after a predetermined time has elapsed since the reset. This control system prevents unnecessary flushing if the system has already been flushed by a dispensing operation.

[0069] The temperature sensors 6 and 7, as well as the flushing valve 4, are connected to the control unit 5 either via wired or wireless connections. These connections are designated by reference numeral 8. The temperature values ​​described above are transmitted as control signals from the temperature sensors 6 and 7, along with control commands, to the flushing valve 4 via this connection. REFERENCE MARK LIST

[0070] 1 Water pipe 2 Pipe inlet 3 Pipe outlet 4 Flushing valve 5 Control unit 6 First temperature sensor 7 Second temperature sensor 8 Connections 9 Tap T1 first temperature T2 second temperature T2_t0 second temperature at start of rinsing process T3 ambient temperature dT temperature difference dTS threshold Q quotient S intersection point EA effective discharge volume SA target discharge volume

Claims

1. Hygiene flushing system comprising a water pipe (1) in which water is conveyed in a flow direction (F), a flush fitting (4) which can be controlled to flush the water pipe (1), a control unit (5) for controlling the flush fitting (4), a first temperature sensor (6) for measuring a first water temperature (T1), and a second temperature sensor (7) for measuring a second water temperature (T2), wherein the second temperature sensor (7) is arranged downstream of the first temperature sensor (6) when viewed in the flow direction (F) of the water, wherein the measured values of the measured temperatures can be transmitted from the temperature sensors (6, 7) to the control unit (5), wherein during a flushing process during which the flush fitting is open so that the water pipe (1) is flushed, a temperature difference (dT) between the first water temperature (T1) and the second water temperature (T2) can be determined by the control unit (5), and wherein the flush fitting (4) can be closed when the temperature difference (dT) reaches a threshold value (dTS), characterized in that the threshold value (dTS) can be calculated as the difference value between the first water temperature (T1) and the second water temperature (T2_t0) at the start of the flushing process and by multiplying the difference value by a quotient (Q); or that the threshold value (dTS) can be calculated as the difference value between the first water temperature (T1) and the ambient temperature (T3) measured by a further temperature sensor at the start of the flushing process and by multiplying the difference value by a quotient (Q).

2. Hygiene flushing system according to claim 1, characterized in that the threshold value (dTS) can be calculated during the flushing process as a function of the measured first water temperature (T1) and / or as a function of the second temperature (T2_t0) measured at the start of the flushing process.

3. Hygiene flushing system according to claim 1 or 2, characterized in that the quotient (Q) is greater than 0, and / or that the quotient (Q) is between 0.1 and 1, in particular between 0.15 and 0.5, and particularly preferred at 0.25.

4. Hygiene flushing system according to one of the preceding claims, characterized in that the threshold value (dTS) can be determined continuously or at fixed intervals during a flushing process.

5. Hygiene flushing system according to one of the preceding claims, characterized in that the hygiene flushing system further comprises at least one tap fitting (9) via which water can be tapped from the water pipe (1), wherein the second temperature sensor (T2) is arranged in the region of the tap fitting (9).

6. Hygiene flushing system according to one of the preceding claims, characterized in that the second temperature sensor (T2) is arranged in the region of the flush fitting (4).

7. Hygiene flushing system according to one of the preceding claims, characterized in that a flushing process can be triggered if the second temperature (T2) remains essentially constant for a predetermined period of time and / or in that a flushing process can be triggered when the second temperature (T2) exceeds a limit value and / or in that a flushing process can be triggered after a predetermined period of time has elapsed after the last flushing process.

8. Hygiene flushing system according to one of the preceding claims, characterized in that the control unit (5) further comprises a time measuring element which detects the time elapsed after a flushing process, wherein during a tapping process it can be determined whether said threshold value (dTS) is reached, and wherein the elapsed time can be reset to zero when the threshold value (dTS) is reached and can be restarted, and wherein a further flushing process can be triggered after a predetermined period of time has elapsed from the zero position.

9. Hygiene flushing system according to one of the preceding claims, characterized in that the temperature sensors (6, 7) are connected in a wireless or wired manner to the control unit (5) for transmitting the measured temperature values; and / or that the flush fitting (4) comprises an electrically controllable valve element, wherein the valve element can be controlled by the control unit (5) in such a way that the valve element is opened at the start of a flushing process and is closed at the end of the flushing process; wherein the valve element is preferably connected in a wireless or wired manner to the control unit (5) for transmitting a control command; and / or that the temperature sensors (6, 7) are arranged such that the water temperature can be measured directly or indirectly; and / or that the temperature sensors (6, 7) are a PT1000 or an NTC element.

10. Method for flushing a water pipe of a hygiene flushing system according to one of the preceding claims wherein an opening of the flush fitting (4) triggers a flushing process so that the water pipe (1) is flushed, wherein during the flushing process a temperature difference (dT) between the first water temperature (T1) and the second water temperature (T2) is determined by the control unit (5), and wherein the flush fitting (4) is closed when the temperature difference (dT) reaches a threshold value (dTS), characterized in that the threshold value (dTS) is calculated as a difference value between the first water temperature (T1) and the second water temperature (T2_t0) at the start of the flushing process and by multiplying the difference value by a quotient (Q); or that the threshold value (dTS) is calculated as a difference value between the first water temperature (T1) and the ambient temperature (T3) measured by a further temperature sensor at the start of the flushing process and by multiplying the difference value by a quotient (Q).

11. Method according to claim 10, characterized in that the threshold value (dTS) is determined during the flushing process as a function of the measured first temperature (T1) and / or the second temperature (T2_t0) measured at the start of the flushing process.

12. Method according to claim 10 or 12, characterized in that the quotient (Q) is greater than 0, and / or that the quotient (Q) is between 0.1 and 1, in particular between 0.15 and 0.5, and particularly preferred at 0.25.

13. Method according to one of the preceding claims 10 to 12, characterized in that the hygiene flushing system further comprises at least one tap fitting (9) via which water can be tapped from the water pipe (1), wherein the second temperature sensor (T2) is arranged in the region of the tap fitting (9).

14. Method according to one of the preceding claims 10 to 13, characterized in that a flushing process is triggered when the second temperature (T2) remains essentially constant for a predetermined period of time and / or that a flushing process is triggered when the second temperature (T2) exceeds a limit value and / or that a flushing process is triggered after a predetermined period of time has elapsed after the last flushing process.

15. Method according to one of the preceding claims 10 to 14, characterized in that the control unit (5) further comprises a time measuring element which detects the time elapsed after a flushing process, wherein in case of a tapping process it is determined whether said threshold value (dTS) is reached, and wherein the elapsed time is reset to zero when the threshold value (dTS) is reached and restarted, and wherein a further flushing process is triggered after a predetermined time period has elapsed from the zero setting; and / or that the flush fitting (4) comprises an electrically controllable valve element, wherein the valve element is controlled by the control unit (5) in such a way that the valve element is opened at the start of a flushing process and closed at the end of the flushing process; wherein the valve element is preferably connected in a wireless or wired manner to the control unit (5) for transmitting a control command; and / or that the temperature sensors (6, 7) are arranged such that the water temperature is measured directly or indirectly.

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