- operating the central pump such that water is conveyed from the upstream side to the downstream side and into the high-pressure conduit system;
- monitoring the flow of water from the upstream side to the downstream side and into the high-pressure conduit system for a predetermined seventh period of time;
- operating a first group of the consumer assemblies such that the inlet valve is open during the seventh period of time, so that water is supplied to the buffer tank of the consumer assemblies of the first group;
- operating a second group of the consumer assemblies such that water is supplied from the buffer tank via the supply device of the consumer assemblies of the second group with the flow of supplied water through the supply device being monitored during the seventh period of time;
- monitoring the level in the buffer tanks of the consumer assemblies of the first and the second group of consumer assemblies during the seventh period of time;
- determining from the change of the monitored level in the buffer tank of the consumer assemblies of the first and the second group of consumer assemblies the total change of the amount of water received in the buffer tanks of the consumer assemblies in the seventh period of time;
- determining by the control unit from the monitored flow of water from the upstream side to the downstream side the total amount of water supplied by the central pump to the consumer assemblies in the seventh period of time;
- determining from the monitored flow of supplied water from the buffer tanks through the supply device of the consumer assemblies of the second group of consumer assemblies the amount of water supplied by the consumer assemblies in the seventh period of time; and
- providing a sixth failure signal when the change of the amount of water received in the buffer tanks in the seventh period of time differs from the total amount of water supplied by the central pump minus the amount of water supplied by the second group of consumer assemblies in the seventh period of time by more than a first predetermined value.

In this preferred embodiment the central pump is operated such that water is supplied to at least a first group of the consumer assemblies and its buffer tanks. However, it is of course conceivable, that the first group includes each of the consumer assemblies so that each consumer assembly is supplied with water via the in the central pump. During the same period of time, i.e., the seventh period of time, in which the first group of consumer assemblies is supplied with water, at least a second group of the consumer assemblies is operated such that water from its buffer tanks is supplied via the supply device.

Furthermore, during the seventh period of time that the flow through the central pump is monitored and integrated in the same is done in relation to the flows from the buffer tanks to the respective supply device is of the consumer assemblies. Moreover, the change of the level in the buffer tanks is monitored as well.

In case the sum of the amount of water supplied by the supply devices and the amount of water resulting from the changes of the level in buffer tanks does not correspond to the amount of water supplied by the central pump, a leak must be present either in the high-pressure conduit system or in one of the monuments. Hence, when there is a mismatch a sixth failure signal will be generated and preferably transmitted via the aircraft data network. In addition, it is of course also conceivable that in case the amounts match with each other, a test-passed signal is generated.

In a further preferred embodiment, each of the plurality of consumer assemblies comprises a buffer tank connected to the high-pressure conduit system and each consumer assembly is configured to supply water from the buffer tank via the supply device, wherein the method according to the disclosure herein further comprises the following steps:

- operating the supply device of one of the consumer assemblies such that water from the buffer tank of the one consumer assembly is supplied via the supply device for an eighth period of time;
- monitoring the filling level in the buffer tank of the one consumer assembly during the eighth period of time; and
- providing a seventh failure signal when the change of filing level in the buffer tank of the one consumer assembly during the eighth period of time is below a second predetermined value.

With this preferred embodiment the supply device and the connection between the buffer tank and the supply device is checked whether there is any kind of blockage. In such case the drop of the filling level in the respective buffer tank would remain below a predetermined value. If this has been detected, a seventh failure signal is generated and transmitted via the aircraft data network. On the other hand, if the decrease in filling level is above the second predetermined value, a test-passed signal may be generated. Therefore, with this preferred embodiment it is possible to check whether the supply devices of the consumer assemblies are operating properly.

In another preferred embodiment the method of the disclosure herein comprises the following steps:

- pressurizing gas, preferably ambient air, in at least one consumer assembly in its line connecting the high-pressure conduit system to the supply device;
- monitoring the pressure in the line connecting the supply device to the high-pressure conduit system of the at least one consumer assembly for a predetermined nineth period of time; and
- providing an eighth failure signal when the pressure in the line connecting the supply device to the high-pressure conduit system of the at least one consumer assembly drops below a predetermined sixth pressure within the nineth period of time.

With this preferred embodiment it can be tested, preferably, when the supply device such as a toilet or a faucet are in a closed position, whether there is a leak in the conduits of a consumer assembly. In this regard it is to be noted that this method can also be applied in case of consumer assemblies having a buffer tank. Then the line being pressurized connects the supply device indirectly with the high-pressure conduit system. It is further preferred, when a pump provided in the line connecting the supply device with the high-pressure conduit system is employed to the pressurize the gas.

Furthermore, it is to be noted that for conducting this preferred embodiment of the method of the disclosure herein it is a requirement that the conduits in the consumer assembly in question are drained so that gas in these conduits can be pressurized.

When it is detected that the gas pressure in the pressurized conduit drops below the predetermined threshold, a corresponding failure signal is generated and transmitted through the aircraft data network (ADN).

In a further preferred embodiment at least one of the plurality of consumer assemblies comprises a buffer tank connected to the high-pressure conduit system and the at least one consumer assembly being configured to supply water from the buffer tank via the supply device, wherein a pump is provided in a line connecting the buffer tank and the supply device of the at least one consumer assembly and wherein the method further comprises the following steps:

- operating the pump of the at least one consumer assembly such that water in the line connecting the buffer tank and the supply device of the at least one consumer assembly is pressurized to a predetermined seventh pressure;
- monitoring the pressure in the line connecting the buffer tank and the supply device of the at least one consumer assembly for a predetermined tenth period of time; and
- providing a nineth failure signal when the pressure in the line connecting the buffer tank and the supply device of the at least one consumer assembly drops below a predetermined eighth pressure within the tenth period of time.

In this preferred embodiment the consumer assembly in question is tested by pressurizing the water in the conduits whether there is a leak. In case a pressure drop is detected after the pump was switched off this indicates the presence of a leak. In such case the corresponding failure signal is transmitted through the aircraft data network (ADN).

In another preferred embodiment a pump is provided in a line connecting the supply device of at least one consumer assembly to the high-pressure conduit system and the method further comprises the following steps:

- operating the pump such that water is conveyed in the line connecting the supply device of the at least one consumer assembly to the high-pressure conduit system;
- monitoring the pressure in the line connecting the supply device of the at least one consumer assembly to the high-pressure conduit system for a predetermined eleventh period of time; and
- providing a tenth failure signal when the pressure in the line connecting the supply device of the at least one consumer assembly to the high-pressure conduit system remains below a predetermined nineth pressure within the eleventh period of time.

With this embodiment it is tested with whether the pump of the consumer assembly in question is operating properly, i.e., whether it is capable of building up a sufficient pressure in the conduit between the high-pressure conduit system and the supply device. In case a sufficient pressure level cannot be reached, a corresponding failure signal will be generated and transmitted via the aircraft data network (ADN). Here, it is to be noted that this method can also be applied in case of consumer assemblies having a buffer tank. Then the line being pressurized connects the supply device indirectly with the high-pressure conduit system.

In a further preferred embodiment, a pump is provided in a line connecting the supply device of at least one consumer assembly to the high-pressure conduit system and wherein the method further comprises the following steps:

- operating the pump such that water is conveyed in the line connecting the supply device of the at least one consumer assembly to the high-pressure conduit system;
- monitoring the flow in the line connecting the supply device of the at least one consumer assembly to the high-pressure conduit system for a predetermined twelfth period of time; and
- providing an eleventh failure signal when the flow in the line connecting the supply device of the at least one consumer assembly to the high-pressure conduit system remains below a predetermined second flow level within the twelfth period of time.

With this embodiment it is tested with whether the pump of the consumer assembly in question is also operating properly and whether, i.e., whether it is capable of providing a sufficient flow in the conduit between the high-pressure conduit system and the supply device, or whether there is a blockage in that conduit. In case such sufficient flow level cannot be reached, a corresponding failure signal will be generated and transmitted via the aircraft data network (ADN). This method can also be applied in case of consumer assemblies having a buffer tank. Then the line being pressurized connects the supply device indirectly with the high-pressure conduit system.

With regard to the disclosure herein and the preferred embodiments explained above it is to be noted that although some embodiments are merely described as being preferred, they are to be considered as a disclosure herein even when taken in isolation.

Furthermore, as can be taken from the above, some of the above embodiments of the method may be applied for on-board water supply systems without buffer tanks. In particular, this applies to those embodiments where the pressure in the high-pressure conduit system is monitored. Hence, the buffer tanks in the consumer assemblies are optional, even though it is preferred that each of the consumer assemblies are provided with such buffer tanks.

BRIEF DESCRIPTION OF DRAWINGS

Moreover, the above object is solved by an onboard water supply and distribution system of an aircraft which is configured to perform any of the above methods.

In the following, the disclosure herein will further be described with regard to the example embodiment shown in the drawings, wherein:

FIG. 1 shows an example embodiment of an aircraft having on-board water supply and distribution system;

FIG. 2 shows a schematic drawing of an example embodiment of an on-board water supply and distribution system of an aircraft;

FIG. 3 shows a schematic drawing of an example embodiment of a consumer assembly of the on-board water supply and distribution system of FIG. 2;

FIG. 4 shows a flow chart of a first example embodiment of a method of the disclosure herein;

FIG. 5 shows a flow chart of a second example embodiment of a method of the disclosure herein; and

FIGS. 6a and 6b show schematic drawings of an embodiment of a pressure reservoir in the high-pressure conduit system.

DETAILED DESCRIPTION

As can be taken from FIGS. 1 and 2 the example embodiment of a water supply and distribution system 1 is generally arranged on-board an aircraft 3 and configured such that it supplies a plurality of consumer assemblies 5 which comprise supply devices 7 such as sinks and toilets in a lavatory or steam ovens and sinks in a galley, with potable water as will be described in detail below. FIG. 1 only schematically shows the arrangement of the system 1 in the aircraft 3, and several types of arrangements are conceivable.

The water supply and distribution system 1 comprises a central water tank 9 which is provided with a connector 11 at its bottom. The connector 11 is connected to a supply line 13 which extends to a fill/drain coupling 15 with a valve 17 being arranged in the supply line 13 adjacent to the fill/drain coupling 15. The valve 17 is connected to a control unit 19 of the system 1 and can remotely be controlled such that it can be switched between a closed and an open position. As can further be taken from FIG. 2, the supply line 13 also connects the connector 11 with a central pump 21. Preferably, the central pump 21 is configured as a positive displacement pump and further preferred as a gear pump or a diaphragm pump.

Furthermore, the central pump 21 is also connected to the control unit 19 and can be operated in a supply mode where it conveys and pressurizes water or other media such as ambient air from its upstream side 23 and the supply line 13 to its downstream side 25 that is connected to a high-pressure conduit system 27 which will be described in detail below. The downstream side 25 of the central pump 21 is equipped with a flow sensor 29 and a pressure sensor 31 which are both connected with the control unit 19 and which are capable of monitoring the flow rate of the water conveyed by the central pump 21 and the pressure the water supplied by the pump 21 has.

In addition, it is to be noted that it is preferred that either the central pump 21 is provided with a backflow prevention mechanism (not shown), which prevents water and/or a gas to flow in an opposite direction from the downstream side 25 to the upstream side 23 when the pump 21 is not operated, or an additional backflow prevention valve (not shown) is provided which is closed, when the central pump 21 is not operated and prevents water and/or a gas to flow from the downstream side 25 to the upstream side 23.

The high-pressure conduit system 27 comprises a plurality of conduits connecting the downstream side 25 of the central pump 21 with the consumer assemblies 5. In addition, in this preferred embodiment, the high-pressure conduit system 27 comprises a pressure reservoir 33 that is configured such that that it applies a pressure at a reservoir pressure level to the high-pressure conduit system 27. The reservoir pressure level being the level the pressure has after operation of the central pump 21 has been stopped so that the reservoir pressure level is the level the pressure in the high-pressure conduit system 27 has at that point in time where the central pump 21 was stopped. The pressure reservoir 33 can be in the form of a tank containing a gas volume and an elastic membrane that separates the gas volume from a further volume being connected to the high-pressure conduit system and receiving water and/or gas such as ambient air from the conduit system, i.e., the pressure reservoir 33 can be configured in a similar form as in conventional compressors. However, any spring element with reversible spring-back behavior may be employed to bias a membrane or a piston which are part of the reservoir 33. Metallic or rubber bellows may also be used. Further, an arrangement with a spring-loaded piston that exerts a pressure on a cylinder connected to the high-pressure conduit system 27 is also conceivable. Finally, the piston in such an arrangement may also be coupled with a linear actuator rather than a spring.

A further embodiment of a pressure reservoir 33 in the high-pressure conduit system 27 is shown FIGS. 6a and 6b. In this embodiment the component of the high-pressure conduit system having compressibility is an elastic hose element 33′. When the water in them high pressure conduit system 27 is not pressurized, the elastic hose element 33′ is not deformed (see FIG. 6a). However, the elastic hose element 33′ has spring back behavior so that it deforms when the water in the high-pressure conduit system 27 is pressurized by the central pump 21, as can be seen in FIG. 6b. In this configuration it applies a pressure on to the water in the system 27 when operation of the pump 21 is stopped, i.e., it acts to maintain the pressure in the system. The consumer assembly 5 shown in FIG. 3 is configured as a lavatory with a sink 35 provided with a faucet 37 and a toilet 39 as supply devices 7. Here, it is to be noted that other forms of consumer assemblies are conceivable such as galleys having sinks etc. and that the disclosure herein is not limited to consumer assemblies in the form of lavatories. In particular, since galleys are provided with buffer tanks that have a larger capacity than those of lavatories, the buffer tanks of galleys may play a more important role in the method of the disclosure herein, as will become clear below.

Furthermore, the consumer assembly 5 comprises a buffer tank 41 having an inlet 43 and an outlet 45, the inlet 43 being provided with an inlet valve 47 which is connected to a control device 49 which in turn is connected to the control unit 19 so that each of the consumer assemblies 5 can be controlled by and can send signals to the control unit 19 via a data network.

The position of the inlet valve 47 can be controlled by the control device 49. The outlet 45 is connected to the faucet 37 and the toilet 39 via a micro pump 51. As can further be taken from FIG. 3, the line connecting the micro pump 51 with the toilet 39 is also provided with a valve 53 that is controlled by the control device 49. Similarly, the line connecting the micro pump 51 with the faucet 37 is also provided with a valve 55 connected to and controlled by the control device 49. Finally, in the lines connecting the outlet of the micro pump 51 with the valves 53, 55 on the toilet 39 and the faucet 37 combined sensors 56 are provided which sensors 56 are configured such that they monitor both the pressure and the flow rate in the line between the respective valve 53, 55 and the micro pump 51. However, it is also conceivable, that a sole combined sensor 56 is provided on the outlet of micro pump 51 so that the output pressure as well as the flow rate which the water is supplied by the micro pump 51 can be monitored by the control unit 19.

The buffer tank 41 of each consumer assembly 5 is provided with a level sensor 57 which is connected to the control device 49 and, hence, also to the control unit 19. The level sensor 57 is configured such that it provides a signal to the control device 49 indicating the fill level in the buffer tank 41.

A similar manner, the central tank 9 is provided with a level sensor 59 that is connected to the control unit 19 so that the fill level in the central tank 9 can also electronically be determined by the control unit 19.

Finally, the inlet 43 of the buffer tank 41 of each of the consumer assemblies 5 is connected to the downstream side 25 of the central pump 21 via the high-pressure conduit system 27 and the inlet valve 47, so that the buffer tanks 41 can be supplied with water by the central pump 21.

The control unit 19 of the system 1 in combination with the control device 49 of each of the consumer assemblies 5 are configured such that they operate the system 1 and especially the central pump 21 in this example embodiment in the following manner:

During normal operation the central pump 21 is constantly or intermittently operated in a supply mode so that water from the central tank 9 is delivered to the consumer assemblies 5 and their buffer tanks 41, which are connected to the downstream side 25 of the pump 21 via the high pressure conduit system 27, so that the buffer tanks 41 of the consumer assemblies 5 are filled. In particular, in this step the inlet valves 47 of those consumer assemblies 5 the buffer tanks 41 of which shall be filled are at the same time or a subsequently brought into its open position. The level in the buffer tanks 41 may be monitored by the level sensors 57. Further, the water may be supplied from the buffer tank 41 to the faucet 37 or the toilet 39 by operating the micro pump 51 and opening the respective valves 53, 55.

In addition, to ensure that the above described system is properly operating and no leaks or blockages are present in the entire system or at least that such leaks or blockages are detected at an early stage, the following safety procedures may be performed by the control unit 19 and the control devices 49 of the consumer assemblies 5 when starting the aircraft or during operation, with the control unit 19 and the control devices 49 being configured correspondingly:

Procedure/Logic 1:

- Operating the central pump 21 such that a gas such as ambient air, drawn in by the pump 21, e.g., via the fill drain coupling 15 or via an overflow line in the central water tank 9, and supplied to the high-pressure conduit system 27 is pressurized to a predetermined pressure monitored by the control unit 19 via the pressure sensor 31;
- operating the consumer assemblies 5 by the control devices 49 such that in each of the consumer assemblies 5 the inlet valve 47 is in a closed position, so that air is prevented from passing from the high-pressure conduit system 27 into the buffer tank 41;
- monitoring the pressure in the high-pressure conduit system 27 with the pressure sensor 31 for a predetermined period of time;
- providing a corresponding failure signal by the control unit 19 to the aircraft data network ADN of the aircraft 3 when the pressure in the high-pressure conduit system 27 drops below a predetermined pressure within the period of time. In particular, a test-passed signal may be transmitted in case the pressure does not drop below the predetermined pressure within the period of time.

With this procedure it can simply be determined whether there is a leak in the high-pressure conduit system 27 without the high-pressure conduit system being filled with water. In turn, it is to be noted that this procedure can only be carried out when the central tank 9 and the high-pressure conduit system 27 must be drained.

Procedure/Logic 2:

- Monitoring the level in the central tank 9, e.g., via the level sensor 59, when the central pump 21 is not operated so that it does not convey water from the upstream side 23 to the downstream side 25; and
- providing a corresponding failure signal by the control unit 19 when the level in the central water tank decreases by more than a predetermined amount within a predetermined period of time.

This procedure allows to determine whether the central tank 9 and the supply line 13 to the central pump 21 comprise any leakages. In case the level in the central tank 21 decreases by more than the predetermined amount, the corresponding failure signal is generated and supplied to the aircraft data network ADN.

Procedure/Logic 3:

- Pressurizing gas, preferably ambient air, in the high-pressure conduit system 27 to a predetermined third pressure, preferably by the central pump 21;
- operating the consumer assemblies 5 such that in each of the consumer assemblies 5 the connection between the buffer tank 41 of the consumer assembly 5 and the high-pressure conduit system 27 is in a closed position by closing the valve 47;
- monitoring the pressure in the high-pressure conduit system 27 for a predetermined period of time by the pressure sensor 31; and
- providing a corresponding failure signal by the control unit 19 to the aircraft data network ADN when the pressure in the high-pressure conduit system 27 drops below a predetermined pressure within the period of time.

With this procedure it can also simply be determined whether there is a leak in the high-pressure conduit system 27. However, this test may also be performed during normal operation, because different from Procedure 1 it is not required that the high-pressure conduit system is filled with gas instead of water.

Furthermore, approaches other than the central pump 29 may by employed as the source for pressurized gas. In particular, a ground pressure source may be used or the high-pressure conduit system 27 may be configured such that it comprises an interface which can connected to an interface of the cabin pressurization system or, as an alternative, it may also be connected to an interface of the bleed air system.

Procedure/Logic 4:

- Operating the central pump 21 such that water is conveyed from the upstream side 23 to the downstream side 25, into the high-pressure conduit system 27 and into the buffer tank 41 of one of the consumer assemblies 5;
- monitoring by the control devices 49 whether the level in the buffer tank 41 of the one of the consumer assemblies 5 increases by more than a predetermined first filling level difference via the level sensors 57;
- providing a corresponding failure signal when the level in the buffer tank 41 of the one of the consumer assemblies 5 has not increased by the predetermined filling level difference within a predetermined period of time, preferably wherein the flow of water from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27 is monitored by the control unit 19 and the flow sensor 29 so that the predetermined period of time is calculated by the control unit 19 based on the monitored flow of water from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27.

Firstly, this procedure allows to determine whether in at least one of the consumers assemblies 5 a leak is present. Further, this procedure generally allows, in combination with Procedure 1 or 3, to determine in which path to the consumer assemblies 5 a leak is present when a failure signal was generated by Procedure 1 or 3. For this purpose, the procedure has to be carried out with the buffer tank 41 of each of the consumer assemblies 5 subsequently being filled until a failure signal is generated (see Procedure 6). Moreover, if Procedures 1 or 2 do not identify a leak, but the time required for achieving a certain difference in the filling level in this procedure is above the predefined limit, a partial or total blockage can also be present (upstream or downstream the pump).

Procedure/Logic 5:

- Operating the central pump 21 by the control unit 19 such that water is conveyed from the upstream side 23 to the downstream side 25, into the high-pressure conduit system 27 and into the buffer tank 41 of at least one of the consumer assemblies 5;
- monitoring whether the level in the buffer tank 41 of the at least one of the consumer assemblies 5 increases by more than a predetermined filling level difference via the control device 49 and the level sensor 57;
- stopping operation of the central pump 21 by the control unit 19 and preferably closing the inlet valve 47, when the level in the buffer tank 41 of the at least one of the consumer assemblies 5 has increased by more than the predetermined filling level difference; further the valves 53, 55 in the conduits to the supply devices 37, 39 are also closed;
- monitoring whether the level in the buffer tank 41 of the at least one of the consumer assemblies 5 decreases by more than a predetermined filling level difference by the level sensor 57 and the control device 49; and
- providing a corresponding failure signal to the aircraft data network ADN by the control unit 19 when the level in the buffer tank 41 of the at least one of the consumer assemblies 5 has decreased by more than the predetermined filling level difference within a predetermined period of time.

This procedure allows to check whether there is any leakage in the monument comprising that consumer assembly 5 the level in the buffer tank 41 is monitored.

Procedure/Logic 6:

- Operating the central pump 21 such that water is conveyed from the upstream side 23 to the downstream side 25, into the high-pressure conduit system 27 and into the buffer tank 41 of each of the consumer assemblies 5, wherein the buffer tanks 41 are subsequently filled such that at one point in time only one of the consumer assemblies 5 is supplied with water;
- monitoring whether the level in the buffer tank 41 of each of the consumer assemblies 5 increases by a predetermined first filling level difference; and
- providing the fourth failure signal when for at least one of the consumer assemblies 5 the time between the start of the filling of its buffer tank 41 and of reaching the predetermined first filling level difference exceeds the predetermined period of time.

Again, the flow of water from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27 can be monitored by the control unit 19 and the flow sensor 29 so that the predetermined period of time is calculated by the control unit 19 based on the monitored flow of water from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27.

When combined with Procedure 5, this procedure allows to check whether any blockages are in the path between the central pump 21 to the buffer tank 41 each of the consumer assemblies 5, because the respective test is conducted for each of the consumer assemblies 5 separately. However, for confirming that a leak or blockage is present in that region it is additionally required that a certain minimum pressure of the pump 21 is reached. Otherwise, the pump 21 could also be damaged or it could have a leak.

Procedure/Logic 7a:

- Operating the central pump 21 by the control unit 19 such that water is conveyed from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27;
- monitoring the pressure in the high-pressure conduit system 27 for a predetermined period of time by the control unit 19 via the pressure sensor 31; and
- providing a corresponding failure signal by the control unit 19 to the aircraft data network ADN when the pressure in the high-pressure conduit system 27 remains below a predetermined pressure within the third period of time.

When Procedures 5 and 6 have subsequently been conducted before and no failure signals were generated, i.e., no leaks and or blockages were detected downstream the central pump 21, this procedure allows to check whether any blockages are present in the path between the central tank 9 and the central pump 21 and whether the central pump 29 is operating properly.

Procedure/Logic 7b:

- Operating the central pump 21 by the control unit 19 such that water is conveyed from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27;
- monitoring the flow of water from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27 for a predetermined period of time by the control unit 19 and the flow sensor 29;
- providing a corresponding failure signal by the control unit 19 to the aircraft data network ADN when the flow of water from the upstream side 23 to the downstream side 25 and into the high-pressure conduit system 27 remains below a predetermined flow level within the predetermined period of time.

Similar to Procedure 7a, this procedure, when combined with Procedure 6, also allows to check whether any blockages are present in the path between the central tank 9 and the central pump 21 and whether the pump is operating in the right manner. Further it is to be noted, that the flow of water through the central pump 21 can be measured by the flow sensor 29 or inverse methods may also be used such as detecting the rotational speed of the central pump 21 to derive the flow if the pressure is measured by the pressure sensor 31 downstream the central pump 21.

Procedure/Logic 8:

- Operating the central pump such that water is conveyed from the upstream side to the downstream side and into the high-pressure conduit system;
- monitoring the flow of water from the upstream side to the downstream side and into the high-pressure conduit system for a predetermined eighth period of time;
- operating a first group of the consumer assemblies such that the inlet valve is open during the predetermined period of time, so that water is supplied to the buffer tank of the of the consumer assemblies of the first group;
- operating a second group of the consumer assemblies such that water is supplied from the buffer tank via the supply device 7 of the consumer assemblies of the second group with the flow of supplied water through the supply device being monitored during the eighth period of time, e.g. by monitoring the level change in the respective buffer tank 41, via operating parameters of the associated micro pump 51, with a flow sensor associated to the supply device or on the basis of a nominal flow value of the respective supply device;
- monitoring the level in the buffer tanks of the consumer assemblies of the first and the second group of consumer assemblies during the eighth period of time;
- determining from the change of the monitored level in the buffer tank of the consumer assemblies of the first and the second group of consumer assemblies the total change of the amount of water received in the buffer tanks (41) of the consumer assemblies in the eighth period of time;
- determining by the control unit 19 from the monitored flow of water from the upstream side 23 to the downstream side the total amount of water supplied by the central pump 21 to the consumer assemblies in the eighth period of time;
- determining from the monitored flow of supplied water from the buffer tanks (41) through the supply device of the consumer assemblies of the second group of consumer assemblies the amount of water supplied by the consumer assemblies in the eighth period of time; and
- providing a seventh failure signal when the change of the amount of water received in the buffer tanks in the eighth period of time differs from the total amount of water supplied by the central pump minus the amount of water supplied by the second group of consumer assemblies in the eighth period of time by more than a predetermined value.

This procedure also allows to determine whether in the path between the central pump 21 and the supply device of the one consumer assembly 5 leaks are present.

Procedure/Logic 9:

- Operating the supply device 7 of one of the consumer assemblies 5 such that water from the buffer tank 41 of the one consumer 5 assembly is supplied via the supply device 7, such as a faucet 37 or toilet 39, for a predetermined period of time;
- monitoring the filling level in the buffer tank 41 of the one consumer assembly 5 during the predetermined period of time; and
- providing a seventh failure signal when the change of filing level in the buffer tank 41 of the one consumer assembly 5 during the eighth period of time is below a second predetermined value.

With this preferred embodiment the supply device, i.e., the faucet 37 or the toilet 39, and the connection between the buffer tank 41 and the supply device 7 is checked whether there is any kind of blockage. In such case the drop of the filling level in the respective buffer tank 41 would remain below a predetermined value. If this is detected a further failure signal is generated and transmitted via the aircraft data network ADN. On the other hand, if the pressure drop is above the predetermined value, a test-passed signal may again be generated.

Therefore, with Procedure 9 it is possible to check whether the supply devices 7 of the consumer assemblies 5 are operating properly.

Procedure/Logic 10a:

- Pressurizing gas, such as ambient air, in at least one consumer assembly 5 in its line connecting the supply device 7, such as the faucet 37 or the toilet 39, to the high-pressure conduit system 27, which can also be the line with the pump 51 connecting the buffer tank 41 and the supply devices 7; in particular, the gas may be pressurized by the pump 51 of the consumer assembly 5;
- monitoring the pressure in the line connecting the supply device 7 of the consumer assembly 5 to the high-pressure conduit system 27 or the buffer tank 41 e.g. via at least one of the sensors 56 for a predetermined period of time; and
- providing an eighth failure signal when the pressure in the line connecting the supply device 5 of the consumer assembly 5 to the high-pressure conduit system 27 or the buffer tank 41 drops below a predetermined pressure within the period of time.

With this procedure it can be tested, preferably when the valve 53, 55 of the supply device 7 such as the toilet 39 or the faucet 37 are in a closed position, whether there is a leak in the conduits of the consumer assembly 5. When it is detected that the gas pressure in the pressurized conduit drops below the predetermined threshold, a corresponding failure signal is generated and transmitted through the aircraft data network (ADN).

Procedure/Logic 10b: