WATER SAVING SYSTEM TO BE USED IN ASSOCIATION WITH WATER

MIXING TAPS"

Field of the invention

The present invention refers to a water mixing system composed by one or more usual mixing taps associated to an accumulation system, and to a specific hydraulic set associated with each mixing tap, such that the whole system allows potable water savings in domestic water installations or in other water installations including mixing taps. Present invention is preferably used by the industry of civil construction, and more precisely on domestic water installations, or other water installations using water mixing systems .

Usual mixing taps for domestic use promote mixing of two water flows, one of hot water and the other of cold water, in order to allow the existence, at the outlet of the mixing tap, of a mixed water flow at a temperature that meets the needs of the user. The temperature of the water leaving the tap is between the temperatures of the inlet flows of cold and hot water entering the mixing tap. The usual mixing taps for domestic use promote, however, potable water losses. In fact, when the user wants hot or partially hot water at the outlet of the mixing tap, but no hot water exists at the mixing tap inlet, the cold or partially cold water at the outlet of the mixing tap under these circumstances does not meet the temperature needs of the user, and it is usually potable water that is directly discharged into the sewage system.

The reason for the non-existence of hot water at the mixing tap inlet is associated with the volume of the duct linking the hot water source (the water heater) to the mixing tap. A period of time exists between the hot or partially hot water demand at the mixing tap outlet, and the hot water existence at the inlet of the mixing tap.

The absence of hot water at the mixing tap inlet, which is relevant for the here proposed system, exists when a hot water demand exists after a period during which no hot water demands existed. This corresponds, therefore, to the situation when the hot water distribution duct is initially filled with cold or partially cold water. During the referred waiting time, the cold or partially cold potable water that leaves the mixing tap does not meet the user temperature needs, and it is usually directly discharged into the sewage system, which is a non-sense from the economical and environmental points of view.

A strong opportunity exists for alternative systems to the usual mixing systems, considering the water saving function, and allowing the use, as potable water, of the cold or partially cold water that, during a given initial period of time, enters the mixing system through the hot water inlet, which is usually directly discharged into the sewage system. Such alternative systems should be applicable to usual domestic installations or in other water installations including water mixing taps, like showers, baths, and lavatories, existing or new, and they should not have significant operation differences when compared with the traditional mixing systems.

Background of the invention

Up to present time some systems have been proposed to allow water savings in domestic or other water installations, the most relevant, accordingly to the present invention, being (by chronological order) :

Document US4750472 refers to a system based on a hot water closed circuit, a driven pump forcing the hot water circulation through the hot water distribution system, in order to guarantee the existence of hot water at the inlet (or nearly at the inlet) of the devices receiving hot water. This is a system trying to partially solve the same problem as that to be solved with the present invention, but the two systems are very different, as the system proposed in document US4750472 uses a pump driven by an electric motor to force the water to return to an accumulation reservoir under pressure or to the inlet of the indoor hot water distribution system. On the contrary, the present invention is a purely mechanical system, without use of any type of pump, and has thus the advantage of no needs of any additional electrical system and the associated electrical installation and electricity consumption. Document US4922943 refers to a system to the return and accumulation of the water leaving the domestic or industrial mixing taps, using the short time periods during which the exit water is not being used (such as, for example, in domestic bath applications, soaping and rub, in order to do not have to adjust the flow and the exit temperature for a new use after the short period during which the exit water was not used. Each hot water device using hot water incorporates an additional manually operated valve with two stable positions, through which is selected if the device should operate normally or if it should operate with the function of return and hot water saving. It is a system whose main objective is to save the water corresponding to the time periods of flow and temperature adjustment to the user needs, which is markedly different from the here proposed system. With the system proposed by US4922943, and taking as example the usual bath operation, only at the beginning of the bath operation the flow and temperature are adjusted to the user needs, and during the bath phases that do not require water the water leaving the tap is conducted to an accumulation system. The normal functions of the tap, water exit to the bath operations or the water accumulation function, are both set by the manually operated additional valve associated to each of the hot water using devices. In this way, water loss associated with the time period for flow and temperature adjustments to the user needs only occur once, at the beginning of the bath operation, and not at the beginning of each of the bath phases requiring hot or partially hot water. System proposed in document US4922943 requires a change on the devices using hot water, in order to include, each of them, an additional manually operated valve with two stable positions, and it is needed a high accumulation capacity reservoir as it is needed to accumulate not only the water corresponding to the initial adjustment of the system to the user needs, but also the water corresponding to the periods when water flows in the tap but it is not used by the user (periods during which the additional valve is commanded in order to direct the water leaving the tap to the accumulation system) . The here proposed system does not require any additional device on the equipments using hot water, it does not require the user operation to select when the water must follow for the normal use or to the accumulation system (the operation mode of the here proposed system is automatic, in terms of the hot water inlet temperature in the mixing system) , and the required accumulation capacity is only that corresponding to the water volume contained in the tube linking the hot water source and the mixing valve.

System proposed by document US5165456 does accumulation of the cold water during the waiting time for hot water at the exit of the used device, from which the water is sent through a mixing tap. However, system proposed by document US5165456 does not consider the integration of the mixing tap and the accumulation system as a whole, while this integration is a crucial part of the present invention. Due to that, with the system proposed by document US5165456 it is not possible to conduct the water entering the hot water inlet of the mixing tap to the accumulation system or to the exit of the mixing tap, depending on the temperature of the water entering the tap through the hot water inlet or on the level of charge of the accumulation system, and the water contained into the accumulation system is not used preferably to the cold water coming from the main cold water distribution system. Another fundamental difference is that with the system proposed by document US5165456 the water that is not lost is not accumulated under pressure, and it is to be used in any other applications or uses different from that which originates it and that do not require pressurized water. With the present invention, the water that is saved is accumulated under pressure and it is later used as cold water by the indoor cold water distribution system, or even to feed the cold water inlet of the mixing tap, that is, it is to be used by the usual appliances using pressurized cold water, including the mixing taps which eventually originated the previous water accumulation.

System proposed by document US6098213 accumulates the cold water when waiting for hot water at the inlet of the mixing tap. However, the system proposed by document US6098213 does not consider the integration of the mixing tap and of the accumulation system as a whole, this integration being crucial as proposed in the present invention. Once again, also with the system proposed by document US6098213 it is not meet the conduction of the water entering the tap through the hot water inlet to the accumulation system or to the exit of the mixing tap as function of the temperature of the water entering the mixer through the hot water inlet or the charge of the accumulation system, and the water contained into the accumulation system is not to be used preferably to the water coming from the main cold water distribution system. Also here a fundamental difference is that with the system proposed by document US6098213 the water that is not lost is not accumulated under pressure, and it is to be used in any other application or use different from that which originates it. With the present invention, the water that is saved is accumulated under pressure and it is later used as water for the appliances receiving cold water from the indoor cold water distribution system, including the mixing taps which eventually originated the previous water accumulation. With system proposed by document US6098213 water that is saved is to be used in applications/uses that do not require pressurized water, like WC cistern filling or manual irrigation .

System initially proposed by document PCT/IB2009/005378 evolved to system later proposed by document PCT/IB2009/055545. System originally proposed by document PCT/IB2009/005378 has essentially the same functioning principles of the system proposed by the document PCT/IB2009/055545. However, the system proposed by the document PCT/IB2009/055545 only requires two external hydraulic connections of the mixing tap (hot water inlet and cold water inlet), as it is also the case for the usual mixing taps and the new or existing installations including them, and the mixing tap of the system proposed by the document PCT/IB2009/005378 requires more than only the referred usual two external hydraulic connections. In order to allow only two external connections (hot water inlet and cold water inlet) of the mixing tap, it is necessary that the selection system of the cold water entering the mixing tap be considerably different from the cold water selector of the system originally considered in document PCT/IB2009/005378, and in this case the cold water selector system is mainly a pressure regulation, or pressure relief valve, which only permits that cold water from the main cold water distribution system enters the mixing tap if the water pressure in the accumulation system or in the indoor cold water distribution system decreases below a pre-established value. The system proposed by document PCT/IB2009/055545 has the advantage that the mixing tap only needs two external hydraulic connections (hot water inlet and cold water inlet), as it is the case for the usual mixing taps and the installations incorporating them, and the system can thus be easily incorporated in preexisting water installations or in new water installations.

System proposed by the present invention is, by its own turn, an evolution of the system proposed by document PCT/IB2009/055545. System proposed by document

PCT/IB2009/055545 has essentially the same functioning principles of the here proposed system. However, the present system has the main differences and advantageous characteristics of requiring only one accumulation reservoir per home or installation, and only one pressure relief valve per home or installation, forming the lonely accumulation system needed for home or installation, and it incorporates usual mixing taps and not special mixing taps specifically conceived to incorporate the mixing system with the water saving function as it is the case of previous systems proposed by documents PCT/IB2009/005378 and

PCT/IB2009/055545. The main core of the proposed system is a specific hydraulic set (presented in Figure 1) to meet the water saving function, which evaluates the temperature of the water coming from the indoor hot water distribution system, and if it is not hot enough to meet the user's requirements it is water that is directed towards the accumulation reservoir and not to the hot water inlet of the mixing tap. To meet the water saving function, each mixing tap requires one associated specific hydraulic set associated to it, which must be as nearest as possible to the mixing tap in order to obtain the best water saving performance. Another characteristic of the here proposed system is that the water accumulated under pressure in the accumulation reservoir can be used to feed any component needing cold water from the indoor cold water distribution system and not only to feed the cold water inlet of the mixing tap which originated the water storage, as it is the case for the systems proposed by documents PCT/IB2009/005378 and PCT/IB2009/055545. However, in the present invention as well as in the systems proposed by documents PCT/IB2009/005378 and PCT/IB2009/055545, the accumulated water in the accumulation reservoir is preferably used than the cold water coming directly from the main cold water distribution system.

General Description of the Invention

The present invention concerns a water mixing system composed by a usual mixing tap, a usual accumulation reservoir, a usual (absolute or differential) pressure relief valve, and a specific hydraulic set, in order to allow water savings in domestic water installations or other. The proposed system, accordingly to the present invention, has characteristics that give it the water saving function. The proposed mixing system uses usual mixing taps, one common accumulation reservoir per home or per water installation, one common (absolute or differential) pressure relief valve per home or per water installation, and a specific hydraulic component to meet the water saving function associated with each mixing tap. System presents considerable changes relative to its previous version as described by document PCT/IB2009/055545, with the objective of requiring only usual mixing taps, only one common accumulation reservoir per home or per water installation, and only one common (absolute or differential) pressure relief valve per home or per water installation. One specific hydraulic component to meet the water saving function is required associated to each mixing tap, which can be easily accommodated near the mixing tap as required for the better water saving performance of the system.

This system is characterized of being composed by:

a) One or more usual mixing taps, each commanded by the two handles setting the hot water (9) and cold water (10) inlets ;

b) One common usual accumulation reservoir (14) per home or per water installation, whose accumulation capacity depends of each particular water installation, as it must accumulate the potable water that were lost if the mixing system with the water saving function was not used;

c) One common usual pressure relief valve per home or per water installation, which includes spring (15), and pistons (16) and (17) linked through the rod (18) (pressure relief valve can be an absolute pressure relief valve, imposing a given pressure after it, as presented in Figure 2, or a differential pressure relief valve, imposing a pressure drop to the water across it, that is, a pressure after it which is a specified value below the pressure of the main cold water distribution system, this alternative form being presented on the right-hand side of Figure 2 ) ; and

d) One or more specific hydraulic sets as presented in Figure 1, each associated with one mixing tap, each specific hydraulic set including a dilatable bulb (2) assembled over a perforated disk (1), the bulb being attached to rod (3) that pushes the perforated sliding piston (4), which is linked through rod (6) to piston (7) which is pushed from the right to the left by the spring (5), and the check valve (8) .

Components referred in b) and c) form the accumulation system, and only one accumulation system is required per home or per water installation.

When opening the hot water inlet (9) of the mixing tap, but no hot water is available at inlet (11) of the mixing system, the cold or partially cold water entering the system through the hot water inlet (11) is conducted to the indoor cold water distribution system (12), or to the accumulation reservoir (14), where it remains stored under pressure. Only when hot water exists at the inlet (11) of the system, or when the accumulation reservoir (14) is fully charged with water, the water entering the system through the hot water inlet (11) is conducted to the discharge (20) of the mixing tap. Water retained in the accumulation reservoir (14) is in permanent contact with the indoor cold water distribution system (12), and it can thus be used to feed any appliance requiring cold water from the indoor cold water distribution system, or even to feed the cold water inlet (12) of the mixing tap, as if it was fresh water coming from the cold water distribution system. The accumulation reservoir (14) and the pressure relief valve are assembled to form the accumulation system, in a way such that the accumulation system gives preference to the use of the accumulated water in the accumulation reservoir (14) to feed the indoor cold water distribution system (12), that is, while water exists in the accumulation reservoir (14) it is conducted to the indoor cold water distribution system (12) or even to the cold water inlet (12) of the mixing tap preferably to the cold water coming from the main cold water distribution system ( 19 ) .

The system is operated by the user as a normal mixing tap through the operation over two handles setting the hot (9) and cold (10) water passages, that regulate the flow rates of hot (13) and cold (12) water inlets in the mixing tap, respectively, represented in Figure 3.

During the period of time when hot or partially hot water is expected at the tap exit (20), but no hot water exists at the hot water inlet (11) of the mixing system and the accumulation reservoir (14) is not fully charged with water, the cold or partially cold water that enters the system through the hot water inlet (11) is conducted to the indoor cold water distribution system or to the accumulation reservoir (14), and during this period of time there is no water discharge at the exit (20) of the mixing tap. Absence of hot water at the hot water inlet (11) is due to the volume of the duct linking the hot water source to the mixing tap, as a time delay exists between the hot water demand at the mixing tap and the existence of hot water at the inlet (11) of the mixing system. Volumetric capacity of the accumulation reservoir (14) is given mainly by the conjugation of two factors: the volume of water that one wants to save, and the volume of the duct linking the hot water source to the mixing tap .

Figures description

Figure 1 - Schematic representation of the proposed specific hydraulic set of the invention, associated to each mixing tap, the numbers referring to:

1 - Perforated and fixed disk;

2 - Dilatable bulb;

3 - Rod;

4 - Perforated piston;

5 - Spring;

6 - Rod linking pistons (4) and (7);

7 - Piston;

8 - Check valve; 11 - Hot water inlet in the mixing system;

12 - Cold or partially cold water exit towards the indoor cold water distribution system, or to the accumulation reservoir (14), which is permanently linked to the indoor cold water distribution system;

13 - Hot water exit of the specific hydraulic set towards the hot water inlet of the mixing tap.

Figure 2 - Schematic representation of the accumulation system, composed by the accumulation reservoir (14) and the pressure relief valve, working together with the usual mixing tap and the proposed specific hydraulic set in Figure 1, where the numbers refer to:

12 - Cold or partially cold water inlet or outlet from or to the indoor cold water distribution system, or cold water outlet towards the cold water inlet of the mixing tap (once the different elements of the system assembled, as presented in Figure 4, points 12 in Figures 1, 2 and 3 are a common shunt point of the system, pertaining to the indoor cold water distribution system) ;

14 - Accumulation reservoir;

15 - Spring;

16 - Piston;

17 - Piston;

18 - Rod linking pistons (16) and (17);

19 - Cold water inlet, from the main cold water distribution system.

[Elements (15), (16), (17) and (18) form the pressure relief valve of the accumulation system. If it is an absolute pressure relief valve, as presented in Figure 2 (main picture) and in the overall system in Figure 4, it imposes a given pressure to the indoor cold water distribution system (12), no matter what the pressure is inside the main cold water distribution system. However, if it is a differential pressure relief valve, as presented on the detail view on the right-hand side of Figure 2 and in the detail view on the right-hand side of Figure 4, it imposes a pressure on the indoor cold water distribution system which is a given value below the pressure in the main cold water distribution system, thus allowing a better performance of the system . ] .

Figure 3 - Usual mixing tap, where the numbers refer to:

9 - Hot water closure/opening inlet;

10 - Cold water closure/opening inlet;

12 - Cold water inlet;

13 - Hot water inlet;

20 - Mixed water exit for normal use.

Figure 4 - Schematic representation of the integrated system with the wanted potable water saving function, composed by the specific hydraulic set in Figure 1, the accumulation system in Figure 2, and the usual mixing tap in Figure 3. Reference numbers in Figure 4 refer to the same elements as indicated before, in Figures 1, 2 and 3, and they are thus addressed through the same reference numbers (once the different elements of the system assembled as in Figure 4, points 12 in Figures 1, 2 and 3 are a common shunt point of the system, pertaining to the indoor cold water distribution system) .

Figure 5 - Schematic representation of the cold and hot water distribution systems to guarantee the proposed system operation and the water saving function, where the numbers refer to:

9 - Indoor hot water distribution system, at pressure Ph>Pc;

12 - Indoor cold water distribution system, at pressure Pc<Pr, where Pr is the pressure of the main cold water distribution system (the accumulation reservoir is permanently linked to this system, as well as the cold water inlet of any system or device using cold water) ;

19 - Cold water inlet, from the main cold water distribution system, at pressure Pr;

21 - Water heater, or hot water source;

22 - Absolute or differential pressure relief valve.

The specific hydraulic set presented in Figure 1 must be placed as close as possible of the mixing tap presented in Figure 3, for a better water saving performance of the system, and it can be made 'invisible' if placed behind the water user pieces and/or even behind or inside its associated furniture. For a better performance, proposed system requires a specific hydraulic set as presented in Figure 1 for each usual mixing tap as presented in Figure 3.

The accumulation system presented in Figure 2 can reside in the most adequate place at home or of the water installation, and thus accumulation reservoir (14) can be large enough in order to allow accumulation of considerable volumes of water with only small increases in pressure. The accumulation system presented in Figure 2 needs not to be placed close to the specific hydraulic set presented in Figure 1, or close to the mixing tap schematically presented in Figure 3. Outlet/inlet (12) of the accumulation system of Figure 2 is permanently linked to the indoor cold water distribution system, and the cold water inlet (12) of any mixing tap or device using cold water is linked to this indoor cold water distribution system. The accumulation system presented in Figure 2 is essentially composed by one usual accumulation reservoir (14) and by one usual pressure relief valve, which can be an absolute pressure or a differential pressure relief valve, composed by elements (15), (16), (17) and (18), and this accumulation system needs to exist only once for a whole home or water installation. If it is an absolute pressure relief valve, as presented in Figure 2 and in the overall Figure 4, it imposes a given pressure Pc to the indoor cold water distribution system, no matter what is the pressure inside the main cold water distribution system. However, if it is a differential pressure relief valve, as presented on the detail view on the right-hand side of Figures 2 and 4, it imposes a pressure Pc on the indoor cold water distribution system which is a given value below the pressure Pr in the main cold water distribution system, thus allowing a better performance of the proposed system.

The expected operation of the system requires its installation through the links between the main cold water distribution system, and the indoor cold and hot water distribution systems as presented in Figure 5. Accordingly to this figure, cold water coming from the main cold water distribution system (19), at pressure Pr, feeds the water heater (21), and the water heater (21) releases hot water to the indoor hot water distribution system (11) at a pressure Ph which is only slightly below the pressure Pr of the main cold water distribution system (this difference of pressure is as small as possible, as imposed by the water heater) .

The proposed system does not present additional difficulties in what concerns its installation which can be divided in two major steps. In the first step, as illustrated in Figure 5: (a) A direct link of the inlet of water heater (21) to the main cold water distribution system (19), thus obtaining the indoor hot water distribution system (11) at the exit of the water heater; (b) The use of a pressure relief valve where cold water coming from the main cold water distribution system (19) enters, thus obtaining the indoor cold water distribution system (12) . Pressure relief valve needs to be regulated in order to guarantee that pressure of water in the indoor cold distribution system, Pc, is below the pressure in the indoor hot water distribution system, Ph. In the second step, as illustrated in Figure 4 as a whole, hot water inlet (11) of the mixing system is linked to the indoor hot water distribution system (11), outlet (12) of the specific hydraulic set in Figure 1 and cold water inlet (12) of the mixing tap in Figure 3 are linked to the indoor cold water distribution system (12), and outlet (13) of the specific hydraulic set in Figure 1 is linked to the hot water inlet (13) of the mixing tap in Figure (3)

It is clear from Figure 4 that the cold water to feed the inlet (12) of the mixing tap, or of any other components that need cold water, comes preferably from the accumulation reservoir (14) and not from the main cold water distribution system through inlet (19) . Only when the pressure in the accumulation reservoir (14) reaches a minimum value, thus meaning that it is almost empty of accumulated water, the cold water enters the mixing system coming directly from the main cold water distribution system through inlet (19) .

Detailed Description of the Invention

The temperature sensor element, which evaluates the temperature of the water at the hot water inlet (11) of the mixing system, is the dilatable bulb (2) in Figure 1, whose volume increase is converted in a horizontal linear deformation (length increase) from left to right, taking Figure 1 as reference.

Initially, the system is at the rest, and both inlets (13, 12) of the mixing tap are totally closed through closures (9, 10), respectively, and consequently there is no outlet water flow (20) leaving the mixing tap. In this non-flow situation, pressure pushing piston (7) to the right equals the pressure of the main cold water distribution system (12), the set formed by pistons (4) and (7) and rod (6) is moved to the right, piston (4) completely opens passage (13) in Figure 1, but no water flow exists through outlet (13) in Figure 1 since passage (9) in Figure 3 is closed. In this initial situation, accumulation reservoir (14) is not fully charged with water, and pressure in the indoor cold water distribution system is that imposed by the pressure relief valve .

If the user wants hot or partially hot water at the exit (20) of the mixing tap, passage (9) is opened , and pressure pushing the set formed by pistons (4) and (7) and rod (6) in Figure 1 to the right considerably decreases, noting that piston (4) is a perforated piston, and spring (5) forces the set formed by pistons (4) and (7) and rod (6) to move to the left, piston (4) closing the passage of the water entering through inlet (11) to the outlet (13) . This is the case when the water entering through inlet (11) is cold or partially cold, the bulb (2) does not increase in length and it does not push rod (3) to the right, and the cold or partially cold water entering through inlet (11) passes through the holes of fixed disk (1), through the holes of piston (4), through the check valve (8), and it is forced to the outlet (12) in Figure 1, thus entering the indoor cold water distribution system and then feeding equipments that need cold water, or then being conducted towards the accumulation reservoir (14) . Accumulation of the cold or partially cold water entering the system through the hot water inlet (11) occurs in this way. If the accumulation reservoir (14) is not completely charged with water or cold water demands exist from the indoor cold water distribution system, during this period no water is being discharged through exit (20) of the mixing tap even if passage (9) is open.

As the accumulation reservoir (14) receives water, pressure inside it increases, as well as pressure in the indoor cold water distribution system, thus also increasing the pressure at which water flow (12) in Figure 1 leaves towards the accumulation reservoir (14) and the indoor cold water distribution system, and also increases the action of this pressure pushing the set formed by pistons (4) and (7) and rod (6) to the right. When the accumulation reservoir is completely charged with water the set formed by pistons (4) and (7) and rod (6) moves to the right, and piston (4) opens passage (13) no matter what the temperature of the water leaving through passage (13) is, which is conducted to the inlet (13) of the mixing tap in Figure 3. Accumulation reservoir (14) has a given limit in its accumulation capacity, and no more water can be accumulated into it once reached this maximum capacity.

If the water entering through the hot water inlet (11) becomes hot, temperature of bulb (2) rises up and it increases in size, and its rod (3) moves to the right, thus forcing the set formed by pistons (4) and (7) and rod (6) to move to the right, and piston (4) opens passage (13) of the hot water entering through inlet (11) towards the inlet (13) of the mixing tap presented in Figure 3 .Water goes then to the mixing chamber of the mixing tap in Figure 3 where it is possibly mixed with the eventual cold water flow entering the mixing tap through its cold water inlet (12) in Figure 3, and then discharged for use through the exit (20) of the mixing tap. This is the normal functioning of the mixing system to satisfy the hot or partially hot water demands of the user.

In this way, water entering through the hot water inlet (11) of the system is directed to the mixing tap exit (20) if the accumulation reservoir (14) is completely filled with water or if the water entering the system through the hot water inlet (11) is sufficiently hot, as sensed by bulb (2) .

The cold or partially cold water accumulated into the accumulation reservoir (14) can be used to feed any equipments or appliances linked to the indoor cold water distribution system, including the cold water inlet (12) of the mixing tap in Figure 3.

When, at the end of one operation of the mixing tap, passage (9) is closed, the set formed by pistons (4) and (7) and rod (6) remains pushed to the right due to the action of the rod (3) of the bulb (2) when the water inside the specific hydraulic system in Figure 1 remains hot, or by the action of the pressure of the main cold water distribution system over piston (7), linked to piston (4) through rod (6) even if temperature of the bulb (2) decreases and its length consequently decreases. Even when the water contained inside the specific hydraulic set in Figure 1 cools down, the set formed by pistons (4) and (7) and rod (6) remains pushed to the right by the action of the pressure of the main cold water distribution system over piston (7), linked to piston (4) through rod (6) . For this non-flow situation, pressure at the hot water inlet (11) of the mixing system is that of the main cold water distribution system.

The cold water flow (12) entering the mixing tap in Figure 3 is always directed towards the exit (20) of the mixing tap, and the water saving function of the proposed system is related with the saving of the water entering the mixing system through the hot water inlet (11) only, when it is not hot but cold, or partially cold. Thus, the functioning of the system is analyzed considering what happens with the water flow entering the system through the hot water inlet (11) only. If it exists, the cold water flow (12) entering the mixing tap in Figure 3 is mixed with the eventual hot water flow entering through inlet (13) of the mixing tap in Figure 3, and the so mixed water leaves through the mixing tap exit (20) to satisfy the user needs.

The accumulation system in Figure 2 is such that the indoor cold water distribution system uses preferably the water accumulated into the accumulation reservoir (14) instead of the cold water coming from the main cold water distribution system through inlet (19) . If an absolute pressure relief valve is used, if pressure in the accumulation reservoir (14) and in the indoor cold water distribution system is higher than the pressure for which the pressure relief valve formed by elements (15), (16), (17) and (18) is regulated, this pressure acts over the right-hand side of piston (17) and the set formed by elements (16), (17) and (18) is forced to move to the left, against action of spring (15), and piston (17) closes the eventual passage of the water entering the system from the main cold water distribution system inlet (19) . If a differential pressure relief valve is used, if pressure in the accumulation reservoir (14) and in the indoor cold water distribution system is higher than the value for which the pressure relief valve formed by elements (15), (16), (17) and

(18) is regulated, this pressure and the spring (15) act over the right-hand side of piston (17), against action of pressure of the main cold water distribution system over the left-hand side of piston (16), and the set formed by elements

(16) , (17) and (18) is forced to move to the left, and piston

(17) closes the eventual passage of the water entering the system from the main cold water distribution system inlet

(19) . Under these conditions, no matter if an absolute pressure or a differential pressure relief valve is used, the indoor cold water distribution system receives water from the accumulation reservoir (14) or from the exits (12) of hydraulic sets like the one in Figure 1, and not cold water coming from the main cold water distribution system (19), thus giving to the proposed mixing system the possibility of use of the accumulated or non-rejected potable water.

After each operation the system is ready for a new operation, which begins from the initial step as described above.

In what concerns operation, the proposed system is operated in the same way as the usual mixing taps, the main difference being that when the water flow entering the mixing system through the hot water inlet (11) is being directed towards the accumulation reservoir (14) or to the indoor cold water distribution system there is none of such water being discharged through the main exit (20) of the mixing tap, thus avoiding water losses that otherwise were discharged directly into the sewage system.

The proposed system does not present additional difficulties in what concerns its installation, which can be divided in two major steps. In the first step, as illustrated in Figure 5: (a) A direct link of the inlet of water heater (21) to the main cold water distribution system (19), thus obtaining the indoor hot water distribution system (11) at the exit of the water heater; (b) The use of a pressure relief valve (22), formed by components (15), (16), (17) and (18), where cold water coming from the main cold water distribution system (19) enters, thus obtaining the indoor cold water distribution system (12) . Pressure relief valve (22) needs to be regulated in order to guarantee that pressure Pc of water in the indoor cold water distribution system is below the pressure Ph in the indoor hot water distribution system. In the second step, as illustrated in Figure 4 as a whole, hot water inlet (11) of the mixing system is linked to the indoor hot water distribution system, outlet (12) of the specific hydraulic set in Figure 1 and the cold water inlet (12) of the mixing tap in Figure 3 are linked to the indoor cold water distribution system, and outlet (13) of the specific hydraulic set in Figure 1 is linked to the hot water inlet (13) of the mixing tap in Figure (3) .