Abstract:
Provided herein is a water saving apparatus configured for purging water from a hot water supply line into a cold water supply line comprising a hot water cavity connected to said hot water supply line for allowing flow of water from said hot water supply line to said first cavity; a cold water cavity connected to said cold water supply line for allowing flow of water from said cold water supply line to said cold cavity and from said hot water cavity to said cold water supply line; a valve configured to block the flow of water between said hot water cavity and said cold water cavity in a first position thereof and to allow the flow of water from said hot water cavity through said cold water cavity and to said cold water supply line in a second position thereof for purging water from said hot water supply line.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of water conservation systems. More particularly, the invention relates to an apparatus for circulating water flowing in the hot water pipes until the water is warm. 
       BACKGROUND 
       [0002]    Many household hot water systems use a central storage-tank type water heater. Each such heater comprises a device for heating the water, and an insulated storage tank for the heated water. A typical household heating tank is equipped with a single storage tank heater from which hot water is piped to the various locations in the house. When hot water is not drawn from the central storage-tank type water heater, the pipes, with the water in them, leading from the heater, cool to the temperature of the surrounding environment, the ambient temperature. When a user opens a hot water faucet, water is received at the ambient temperature. Hot water of the desired temperature only reaches the faucet after the cooled water is removed from the pipes, and enough hot water has flowed through the pipes to warm the pipes. 
         [0003]    The initial water drawn from the hot water faucet, the cooled water at ambient temperature, is often wasted. Before taking a shower, a user will typically turn on the hot water faucet, allowing the received potable water to run down the drain in waste. When the water at ambient temperature is purged from the pipes, and hot water reaches the faucet, the user will adjust the temperature and enter the shower. Other users may turn on the hot water, allowing potable water to flow down the drain, while performing some unrelated task. Sometime later, after hot water has reached the faucet, the user will return to the shower, adjust the temperature, and begin the shower. This not only wastes potable water and energy related to water heating, but also increases the load on the sewage system being used because of the increase in volume of liquid sewage to be treated. 
         [0004]    According to some embodiments, a family of four people may waste more than 3 cubic meters of water a month waiting for hot water for a shower, for shaving, for washing dishes, etc. A larger family will waste even more potable water. It is therefore advantageous if the loss of this water can be prevented. 
         [0005]    The amount of water wasted while purging hot water pipes can be reduced through use of a demand-type water heater located close to the faucet. Multiple demand-type water heaters are often required if water wastage is to be eliminated because the various faucets are not always located close to each other. Further, demand-type water heaters are usually electric water heaters and are significantly less efficient than natural gas fired heaters of the storage tank type. 
         [0006]    Another method for reducing the amount of water wasted while purging pipes is the continuously circulating hot water systems. With these systems, the pipes leading from the hot water heater are arranged in a loop, passing near each faucet, with a return pipe to the hot water heater. A pump is inserted in the loop to keep hot water flowing through the loop, thereby keeping the pipes and the water in them at a high temperature. This system is not energy efficient because of the heat transfer from the pipes to the environment and the energy wasted in water circulation. Such a system is also difficult to retrofit to existing buildings. This system is nonetheless common in large buildings with many bathrooms such as hospitals or hotels. 
         [0007]    U.S. Pat. No. 5,277,219 shows a water saving system wherein an electric pump is used to pump ambient temperature water from the hot water pipe into the cold water pipe. A switch is pressed to turn on the pump when hot water is desired. The pump turns off when a temperature sensor detects that the cool water has been purged from the hot water pipe. A similar system is portrayed in U.S. Pat. No. 5,105,846 in which a timer shuts off the electric pump. Yet another such system is portrayed in U.S. Pat. No. 5,009,572. Nevertheless, such systems are somewhat complex to install, maintain, and operate. 
         [0008]    There is still a need in the art for water conservation systems that would allow better saving of water and energy. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to provide an apparatus for reserving the cooled water in the hot water supply line. 
         [0010]    It is another object of the present invention to provide hot water (or water at a predetermined temperature) per demand (for example, per demand of a user) without providing cold or not sufficiently warm water first. According to some embodiments, the apparatus is adapted to purge the hot water supply line from cold or not sufficiently warm water prior to allowing the water to be available to the user. The Apparatus thus facilitates saving water and energy. According to some embodiments, the apparatus and methods of the present invention, are adapted to purge the hot water supply line from cold or not sufficiently warm water by directing the cold or not sufficiently warm water to the cold water supply line, per demand. According to some embodiments, the apparatus and methods of the present invention, allow a user to control the apparatus and decide if and when to activate the purging of the hot water supply line from cold or not sufficiently warm water, as per his/her needs, habits, requirements, or the like. For example, a user may decide to activate (by using the activator) the purging of the hot water supply line prior going into the shower or the user may decide to automatically activate the purging of the hot water supply line every predetermined period of time. The user may also decide to stop the purging of the hot water supply line at any time for example if no hot water are available at all. The activator may be configured for manual or automatic operation. For example, the activator may be configured to automatically stop purging the hot water supply line upon detection that no hot water are available, for example after a predetermined period of time when no hot water were sensed. According to some embodiments, the apparatus may be configured to be positioned at any location (for example, between a hot water supply line and to a cold water supply line) and to be connected to the hot water supply line and to the cold water supply line. The apparatus may be positioned adjacent to a water faucet or remotely from one or more water faucets. 
         [0011]    It is still another object of the present invention to provide a method for reserving water, for example in households, industrial facilities, hospitals, offices and the like, without requiring a complex modification to the household water supply system. 
         [0012]    Other objects and advantages of the invention will become apparent as the description proceeds. 
         [0013]    According to some embodiments, there is provided an apparatus comprising a valve (for example, a thermostatically controlled valve) comprising an actuator (for example a thermally sensitive actuator) configured to bypass water from a hot water supply line to a cold water supply line 
         [0014]    until a certain condition is reached (for example the temperature of the water is at a predetermined value). The apparatus further comprises an activator configured to allow a user to control the valve and thus control the beginning and/or ending of the bypassing of water from the hot water supply line to the cold water supply line. 
         [0015]    According to some embodiments, there is provided an apparatus for purging water from a hot water supply line into the cold water supply line comprising: 
         [0016]    a first water port (for example, first water port  20 ) connected to the hot water supply line, for allowing flow of water from the hot water supply line to the apparatus; 
         [0017]    a second water port (for example, second water port  10 ) connected to the cold water supply line for allowing flow of water from the first water port to the cold water supply line, and or from the cold water supply line to the apparatus; 
         [0018]    a valve configured to stop the flow of water between the first water port and the second water port in a first position thereof and to open allow the flow of water from the first water port through the second water port and to the cold water supply line in a second position thereof for purging water from the hot water supply line; 
         [0019]    a mechanism configured to, directly or indirectly, shift the valve from the first position to the second position; 
         [0020]    an activator configured to operate the valve. 
         [0021]    According to some embodiments, operating the valve by the activator comprises shifting the valve from first position to a second position of the valve and/or from a second position to a first position of the valve. 
         [0022]    According to some embodiments, the mechanism comprises a thermal mechanism adapted to change one or more dimensions or form thereof as a function of temperature (for example, expand at higher temperatures and reduce its size at lower temperatures) and as a result actuates another element such as a valve. 
         [0023]    According to some embodiments, the valve activating mechanism comprises a manual actuator and a thermal mechanism adapted to move the valve between the two positions. 
         [0024]    According to some embodiments, the thermal mechanism, may include a pellet. The thermal pellet may include, for example wax, which may or may not include additives such as metal(s) particles, such as cupper and/or aluminum particles. 
         [0025]    In one embodiment, the thermal mechanism may include a bimetal element. 
         [0026]    In one embodiment, the mechanism comprises a timer. 
         [0027]    The activator may be a button, such as a push button and/or a pull button. In one embodiment, the activator is a cord. In one embodiment, the activator is a switch. In one embodiment, the activator is a lever. In one embodiment, the activator is a chain. In one embodiment, the activator is a push rod. 
         [0028]    According to one embodiment, the activator may be configured for manual operation. According to one embodiment, the activator may be configured for automatic operation. 
         [0029]    According to one embodiment, there is further provided a system for circulating water from a hot water supply line into the cold water supply line, the system comprising: 
         [0030]    an apparatus comprising: 
         [0031]    a first water port (for example, first water port  20 ) connected to the hot water supply line, for allowing flow of water from the hot water supply line to the apparatus; 
         [0032]    a second water port (for example, second water port  10 ) connected to the cold water supply line for allowing flow of water from the first water port to the cold water supply line; 
         [0033]    a valve configured to stop the flow of water between the first water port and the second water port in a first position thereof and to open allow the flow of water from the first water port through the second water port and to the cold water supply line in a second position thereof for purging water from the hot water supply line; 
         [0034]    a mechanism configured to, directly or indirectly, shift the valve from the first position to the second position; and 
         [0035]    an activator configured to operate the valve; and 
         [0036]    a water faucet connected to a third and a fourth water ports (such as water ports  21  and  11 ) of the apparatus. The water faucet may include a Thermal faucet. 
         [0037]    According to one embodiment, there is further provided a water saving apparatus configured for purging water from a hot water supply line into a cold water supply line comprising: 
         [0038]    a hot water cavity connected to the hot water supply line for allowing flow of water from the hot water supply line to the first cavity; 
         [0039]    a cold water cavity connected to the cold water supply line for allowing flow of water from the cold water supply line to the cold cavity and from the hot water cavity to the cold water supply line; 
         [0040]    a valve configured to block the flow of water between the hot water cavity and the cold water cavity in a first position thereof and to allow the flow of water from the hot water cavity through the cold water cavity and to the cold water supply line in a second position thereof for purging water from the hot water supply line; 
         [0041]    a mechanism configured to, directly or indirectly, shift the valve from the first position to the second position; and 
         [0042]    an activator configured to shift the valve from the first position to the second position per demand. 
         [0043]    According to one embodiment, there is further provided a water saving faucet comprising: 
         [0044]    a water saving apparatus for purging water from a hot water supply line into a cold water supply line, the apparatus comprises: 
         [0045]    a hot water cavity connected to the hot water supply line for allowing flow of water from the hot water supply line to the first cavity; 
         [0046]    a cold water cavity connected to the cold water supply line for allowing flow of water from the cold water supply line to the cold cavity and from the hot water cavity to the cold water supply line; 
         [0047]    a valve configured to block the flow of water between the hot water cavity and the cold water cavity in a first position thereof and to allow the flow of water from the hot water cavity through the cold water cavity and to the cold water supply line in a second position thereof for purging water from the hot water supply line; 
         [0048]    a mechanism configured to, directly or indirectly, shift the valve from the first position to the second position; and 
         [0049]    an activator configured to operate the valve per demand; and 
         [0050]    a mixing valve controlled by a handle, the mixing valve is configured to allow a user to adjust (by the handle) the water temperature and the amount of mixed water exiting the faucet. 
         [0051]    According to one embodiment, there is further provided a water saving system comprising: 
         [0052]    a water saving apparatus for purging water from a hot water supply line into a cold water supply line, the apparatus comprises: 
         [0053]    a hot water cavity connected to the hot water supply line for allowing flow of water from the hot water supply line to the first cavity; 
         [0054]    a cold water cavity connected to the cold water supply line for allowing flow of water from the cold water supply line to the cold cavity and from the hot water cavity to the cold water supply line; 
         [0055]    a valve configured to block the flow of water between the hot water cavity and the cold water cavity in a first position thereof and to allow the flow of water from the hot water cavity through the cold water cavity and to the cold water supply line in a second position thereof for purging water from the hot water supply line; 
         [0056]    a mechanism configured to, directly or indirectly, shift the valve from the first position to the second position; and 
         [0057]    a pump configured to increase hot water pressure in the hot water supply line upon indication of a decrease, below a predetermined value, in a differential pressure between the hot water supply line and the cold water supply line. 
         [0058]    Such pump may be adapted to operate to increase hot water pressure only when the differential pressure between hot and cold water decreases below a preset value. This way the pump is activated only when needed and energy is saved. The differential pressure may be detected by differential pressure sensor(s) connected to hot and cold water lines. 
         [0059]    According to some embodiments, the mechanism may include a thermal mechanism. According to some embodiments, the thermal mechanism may include a pellet. The thermal pellet may include, for example wax, which may or may not include additives such as metal(s) particles, such as cupper and/or aluminum particles. In one embodiment, the thermal mechanism may include a bimetal element. 
         [0060]    According to some embodiments, the thermal mechanism may be adapted to shift the valve from the second position back to the first position when the temperature of the water increases to a predetermined value, thereby the flow of water from the hot water cavity through the cold water cavity and to the cold water supply line is stopped. 
         [0061]    According to some embodiments, the mechanism may include a timer. The timer may stop the flow of water from the hot water cavity through the cold water cavity and to the cold water supply line after a predetermined period of time. 
         [0062]    According to some embodiments, the activator may be configured for manual operation. The activator may be selected from a group consisting of: a button, a cord, a switch, a lever and a chain. 
         [0063]    According to some embodiments, the valve may essentially be in a cylindrical shape and wherein the mechanism is a thermostatic working element, the valve is configured to change its position upon a change of temperature of the thermostatic working element and upon activation of the activator by a user, such that: in a first position of the apparatus, the valve blocks water flow between the hot water cavity and the cold water cavity, and upon activation of the activator, in a second position of the apparatus, the valve is positioned to allow water flow between the hot water cavity and the cold water cavity and thus allowing bypassing of water from the hot water supply line to the cold water supply line until water temperature increases to a predetermined value and the apparatus is shifted to a third position, wherein the valve blocks water flow between the hot water cavity and the cold water cavity and the water bypassing is stopped. 
         [0064]    According to some embodiments, the valve may essentially be in a hollow cylindrical shape and wherein the mechanism is a thermostatic working element and is located inside the valve, the valve comprises one or more openings, the valve and the thermostatic working element are configured to move (for example, along the length axis of the cylinder) with respect to one another upon activation of the activator and upon a change of temperature of the thermostatic working element, such that: in a first position of the apparatus, the valve blocks water flow between the hot water cavity and the cold water cavity, and in a second position of the apparatus and upon activation of the activator, the valve is positioned with respect to thermostatic working element to allow water flow (through the one or more openings thereof) between the hot water cavity and the cold water cavity and thus allowing bypassing of water from the hot water supply line to the cold water supply line until water temperature increases to a predetermined value and the apparatus is shifted to a third position, wherein the valve blocks water flow between the hot water cavity and the cold water cavity and the water bypassing is stopped. 
         [0065]    The third position may be achieved by the extraction of a pin from the thermostatic working element. 
         [0066]    According to some embodiments, upon a decrease of water temperature the pin is retracted back inside the thermostatic working element and the apparatus is configured to return to the first position. According to some embodiments, the apparatus further includes a spring configured to starch and facilitate the return of the apparatus to the first position. 
         [0067]    According to some embodiments, there is further provided a method for water saving by purging water from a hot water supply line into a cold water supply line using anyone of the apparatuses, faucets and/or systems described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0068]      FIG. 1 a    shows a cross section of a water saving apparatus, set in its first position, according to an embodiment of the invention. 
           [0069]      FIG. 1 b    shows a cross section of the water saving apparatus of  FIG. 1   a,  set in its second position, according to an embodiment of the invention. 
           [0070]      FIG. 1 c    shows a cross section of the water saving apparatus of FIGS,  1   a - b,  set in its third position, according to an embodiment of the invention. 
           [0071]      FIG. 2 a    shows a cross section of a water saving apparatus, set in its first position, for continuously circulating hot water systems, according to some embodiments of the invention. 
           [0072]      FIG. 2 b    shows a cross section of the water saving apparatus of  FIG. 2 , set in its second position, according to some embodiments of the invention. 
           [0073]      FIG. 3 a    shows an exploded view of a typical mixing faucet. 
           [0074]      FIG. 3 b    shows an exploded view of a mixing faucet including a water saving unit, according to some embodiments of the invention. 
           [0075]      FIG. 4 a    shows a cross section of a water saving unit in a first position, according to some embodiments of the invention. 
           [0076]      FIG. 4 b    shows a cross section of the water saving unit of  FIG. 4 a    in a second position, according to some embodiments of the invention. 
           [0077]      FIG. 4 c    shows a cross section of the water saving unit of  FIGS. 4 a - b    in a third position, according to some embodiments of the invention. 
           [0078]      FIG. 5 a    shows a cross section of a thermostatic working unit in a first position, according to some embodiments of the invention. 
           [0079]      FIG. 5 b    shows an isometric view of the thermostatic working unit of  FIG. 5 a    in the state position, according to some embodiments of the invention. 
           [0080]      FIG. 5 c    shows a cross section of the thermostatic working unit in a second position, according to some embodiments of the invention. 
           [0081]      FIG. 5 d    shows an isometric view of the cross section of the thermostatic working unit of  FIG. 5 c    in the second position, according to some embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0082]      FIG. 1 a    shows a cross section of a water saving apparatus  100 , set in its first position, according to embodiments of the invention. Apparatus  100  may be configured to be positioned between water supply lines, hot and cold (not shown) and a faucet (tap) (not shown). Water port  10  is connected to the cold water supply line and configured to receive cold water therefrom. Water port  10  is in fluid flow connection (for example, via a cavity) to port  11 . Port  11  is connected to the faucet. Port  10  may also be in fluid flow connection with ports  20  and  21  depending on the position of valve  40 .  FIG. 1 a    shows water saving apparatus  100 , set in its first position wherein valve  40  is in a closed position preventing flow of water between ports  20 / 21  and  10 / 11 . 
         [0083]    Water port  20  is connected to the hot water supply line. On the other side of the apparatus, water port  21  is connected to the faucet. 
         [0084]    In this first position valve  40  is in its closed position, located in the (narrow) passage of cavity  80 , effectively acting as a barrier and thus essentially blocking the flow of water from port  20  to port  10 . Valve  40  may be any valve or any other device which can prevent the flow of water in cavity  80 , which connects between port  20  and port  10 . At this position mechanism  30  is at ambient temperature and it is closed, such that the pin  60  is fully retracted in mechanism  30 . 
         [0085]    In one of the embodiments mechanism  30  is a thermostatic working element which may also be referred to as a thermal pellet. In this embodiment when the temperature around the pellet increases, the material inside the pellet starts to expand, effectively extracting pin  60 . In this embodiment, the mechanism  30  may be a wax pellet, a bimetal pellet or any other pellet or device which expands in reaction to heat, or any other mechanism which expands in reaction to the flow of water or the passing of time. Apparatus  100  further comprises a spring  50  located essentially around mechanism  30 . In the first position, spring  50  is in a position for holding mechanism  30  in a closed position such that pin  60  is fully retracted inside mechanism  30 . In this embodiment, the water pressure in the hot water supply line is greater than the water pressure in the cold water supply line, for reasons that will be described in relations to  FIG. 1   b.  Higher water pressure in the hot water supply line may be achieved in a variety of ways such as attaching an auxiliary pump in the hot water supply line. In one embodiment the auxiliary pump is automatically activated in response to water flow in the hot water supply line, or in response to a drop in water pressure in the hot water supply line, or in response to a changing difference in the pressure between the hot water supply line and the cold water supply line. In one of the embodiments a seal  90 , such as a rubber O-ring, may be added to valve  40 , for effectively sealing the barrier between the flow of cold water and the flow of hot water. As shown valve  40  is connected to activator  70  which can shift valve  40  from its closed position to its open position. Activator  70  may be a button, as shown, a cord, a switch, a lever, a chain or any other activating mechanism capable of shifting valve  40  to its open position. In one embodiment, activator  70  has two circular cavities  74  and  75  carved around its axis for sustaining it in one of its two positions. As shown, activator  70  is sustained in the first position by a ball  71  pressed in the first cavity  74 . The ball  71  may be pressed into place by a spring  72  which is sustained by a closing bolt  73 . 
         [0086]      FIG. 1 b    shows a cross section of water saving apparatus  100 , set to its second position, according to an embodiment of the invention. The second position occurs after the activator  70  is shifted to its second position. The second position may be activated by the user, effectively allowing the user to decide when he requests warm water. In one embodiment, the activator  70  may be a button, and it is shifted to its second position by pressing. When activator  70  is shifted to its second position, water flow passage between port  20  and port  10  is obtained. This may be achieved for example, as follows: ball  71 , which sustained the activator  70  in its first position, is pushed out and pressed back into the second cavity  75 , to sustain the activator  70  in its second position. When activator  70  is shifted to its second position, valve  40  is shifted in channel  80 , from its left narrow passage to its right wider passage, effectively opening the water passage between port  20  to port  10 . Since the water pressure in the hot water supply line is greater than the water pressure in the cold water supply line, and since the faucet is closed and water cannot flow through ports  21  and  11 , cold water from the hot water port  20  flows into the cold water port  10 . While the cold water flows from the hot water supply line to the cold water supply line, the cold water, in the hot water supply line, is replaced by warmer water. The term “cold water” may include, according to some embodiments, water originated from the hot water supply line, which were cooled during a period of time (for example to ambient temperature). As the flow of water continues from water port  20  to water port  10  the temperature of the flowing water increases as heated water arrives from the hot water supply line. The increased temperature of the water heats the surrounding including mechanism  30 . 
         [0087]      FIG. 1 c    shows a cross section of water saving apparatus  100 , set to its third position, according to an embodiment of the invention. In this position the warm water flowing from hot water supply line port  20  have heated mechanism  30  which is designed to extract pin  60  upon warming. Heated mechanism  30  has extracted pin  60 , effectively closing the passage in channel  80  by shifting valve  40  to its closed position, blocking the flow of water from port  20  to port  10 . In one embodiment when valve  40  is shifted, activator  70  is also shifted outwards, effectively indicating to the user that the water in the hot water supply line is warm. At this point when the user may open the hot water knob in the faucet, and the warm water flows directly from the hot water supply line through port  20  and through the hot water port  21  to the hot water outlet of the opened faucet. 
         [0088]    In one of the embodiments the described apparatus of  FIG. 1 a    to  1   c,  is connected between the hot and cold water supply lines respectively, far from the faucet, instead of connecting the apparatus to the faucet directly. In one embodiment the described apparatus of  FIG. 1 a  to 1 c    is hidden from the sight of the customer and may be operated using a chain or lever connected to activator  70 , or instead of activator  70 , for the user to operate. 
         [0089]    In one of the embodiments the mechanism  30  described in  FIGS. 1 b  and 1 c    is a timer pellet. When the activator  70  is pressed, as shown in  FIG. 1   b,  and water starts flowing from hot water supply line port  20  to cold water supply line port  10 , the mechanism  30  is closed for a preset time such as 1 minute. After the preset time expires, mechanism  30  extracts pin  60 , as shown in  FIG. 1   c,  and shifts valve  40  to its closed position, which acts again as a barrier blocking the flow of water from port  20  to port  10 . In another embodiment the described mechanism  30  is a rotary piston measuring the flow of water. Once a preset amount of water has flowed in channel  80 , mechanism  30  extracts pin  60 , effectively shifting piston  40  to its closed position as described above. 
         [0090]    In one of the embodiments the described apparatus is used with a Thermal Tap, where the apparatus may be fixed between the water supply lines and the Thermal Tap or may be implemented in the Thermal Tap for reserving the cooled water from the hot water supply line. 
         [0091]      FIG. 2 a    shows a cross section of water saving apparatus  200 , set in its first position, configured to continuously circulate hot water systems, according to another embodiment of the invention. In these systems, the pipes leading from the hot water heater are arranged in a loop, passing near each tap, with a return pipe to the hot water heater. A pump is inserted in the loop to keep hot water flowing through the loop, thereby keeping the pipes and the water in them at a high temperature. In this embodiment the depicted apparatus is intended to be connected in the hot water supply line loop (not shown), where the water flow is designed to flow from water outlet  210  to water outlet  211 . In one embodiment the apparatus&#39;s outlets are covered by gaskets and nuts which can be tightly screwed on the water supply line. In this first position valve  240  is in its open position, allowing water to flow from water outlet  210  to water outlet  211 . At this position the mechanism  230  has an ambient temperature and therefore it is closed, meaning that the pin  260  is retracted maximally in mechanism  230 . When the temperature around mechanism  230  increases, the material inside the mechanism  230  will start to expand, effectively extracting pin  600 . The mechanism  230  may be a wax pellet, a metal pellet or any other pellet or device described in relations to  FIGS. 1 a   - c.  In one of the embodiments the pellet is designed to achieve its full expansion at a temperature of at least 35° C. In this position spring  500  task is to hold the pellet  300  closed with pin  260  squeezed inside. 
         [0092]      FIG. 2 b    shows a cross section of the water saving apparatus of  FIG. 2 a   , set in its second position, intended for continuously circulating hot water systems. In this position the warm water that had flowed from outlet  210  to outlet  211  have heated the pellet  300  which is designed to extract pin  260  upon warming. The heated pellet  300  has extracted pin  260 , effectively closing the passage and stopping the water flow by shifting valve  240  to its closed position, which acts as a barrier between outlet  210  and outlet  211 . Thus when the water is warm enough the circulating stops, effectively saving energy. However, when the water cools down and the pellet  230  cools down to its close position, the apparatus is switched to its first position and the hot water circulation continues. In one of the embodiments a seal  290 , such as a rubber O-ring, may be added to valve  240 , for effectively sealing the barrier and stopping the water flow. 
         [0093]    Reference is now made to  FIG. 3 a   , which shows an exploded view of a typical mixing faucet  300  and to  FIG. 3 b   , which shows an exploded view of a mixing faucet  400  which includes a water saving unit  350 , according to some embodiments of the invention. 
         [0094]    Faucets  300  and  400  both include a mixing valve  310 , controlled by handle  311 , and a faucet base  320 . Mixing valve  310  is configured to allow a user to adjust (via handle  311 ) the water temperature and the amount of mixed water exiting the faucet (by mixing hot/cold water and regulating the flow of mixed water). 
         [0095]    Faucet base  320  includes port  322  connected to the cold water supply line, port  324  connected to the hot water supply line and port  326  which is connected to the faucet outlet such as a shower head etc. Faucet base  320  further includes port  328  configured to pass cold water from the cold water supply line to mixing valve  310 , port  330  configured to pass hot water from the hot water supply line to mixing valve  310  and port  332  configured to pass mixed water from mixing valve to the faucet outlet such as shower outlet etc. 
         [0096]    Mixing valve  310  of faucet  300  ( FIG. 3 a   ) is connected directly to faucet base  320 . 
         [0097]    Mixing valve  310  of faucet  400  ( FIG. 3 b   ) is connected to faucet base  320  through water saving unit  350 . Water saving unit  350  comprises a main body  352  and an activator  354  and is configure to connect on one end to faucet base  320  and on its other end to mixing valve  310 . Water saving unit  350  further includes port  356  configured to pass cold water from cold water supply line to mixing valve  310 , port  358  configured to pass hot water from hot water supply line to mixing valve and port  360  configured to pass mixed water from mixing valve  310  to the faucet outlet such as shower outlet etc. 
         [0098]    Reference is now made to  FIGS. 4 a   - 4   c,  which show cross sections of a water saving unit  350  in first, second and third positions, respectively, according to some embodiments of the invention. As seen in  FIGS. 4 a   - 4   c,  water saving unit  350  includes valve assembly  370  (in this case, a sliding valve assembly is described, but other valve assemblies are also included under the scope of this invention, for example, spiral valve assemblies, rotating valve assemblies or any other type of valve assembly), cold water cavity  362 , hot water cavity  364  and mixed water cavity  366 . 
         [0099]    Cold water cavity  362  of water saving unit  350  is connected on one side to port  328  of faucet base  320  and on another side to port  356 . Hot water cavity  364  water saving unit  350  is connected on one side to port  330  of faucet base  320  and on another side to port  358 . Cold water cavity  362  and hot water cavity  364  may be in water flow connection with each other or separated from each other depending on the position of water saving unit  350 , or more specifically, the position of valve assembly  370 , as described hereinbelow. 
         [0100]    Reference is also made to  FIG. 5 a   , which shows a cross section of valve assembly  370 , in a first state (pin  378  is fully retracted in thermostatic working element  372 ), according to some embodiments of the invention, to  FIG. 5 b   , which shows an isometric view of the cross section of valve assembly  370  in the first state, according to some embodiments of the invention, to  FIG. 5 c   , which shows a cross section of the valve assembly  370  in a second state (pin  378  extracted from thermostatic working element  372 ), according to some embodiments of the invention and to  FIG. 5 d   , which shows an isometric view of the cross section of the valve assembly  370  in the second position, according to some embodiments of the invention. 
         [0101]    Valve assembly  370  is located within body  352  of saving unit  350  and comprises thermostatic working element,  372 , valve body  374 , spring  380  and activator interface  376  (connected to activator  354  as seen in  FIG. 3 b   ). Thermostatic working element  372  includes a pin  378  inserted (retracted) within thermostatic working element  372  to an extent which depends on the surrounding temperature. Spring  380  is located essentially around thermostatic working element  372 , between the thermostatic working element  372  and valve body  374 , for example, in cavity  390 . 
         [0102]    Valve  374  has an essentially cylindrical shape and includes one or more openings, such as an opening  386 , an opening  388  (there may be more openings) (also seen in  FIGS. 4 a - c   ) and a bottom opening  392 . At its top part, valve  374  has or connected to activator interface  376  extending therefrom. 
         [0103]    When valve assembly  370  is in a first state (as shown in  FIGS. 5 a - b   ), pin  378  is maximally retracted in thermostatic working element  372  and the bottom part of thermostatic working element  372  is positioned within bottom opening  392  of valve body  374 , but does not protrude therefrom. When thermostatic working element  372  is heated pin  378  is extracted out from thermostatic working element  372  and pushes valve assembly  370  to a second position (as shown in  FIGS. 5 c - d   ). 
         [0104]      FIG. 4 a   , shows a cross section of a water saving unit  350  in first positions, in which valve assembly  370  is in a first position (as shown in  FIGS. 5 a - b   ), 
         [0105]    In first position ( FIG. 4 a   ) valve assembly  370  is in its closed position, effectively acting as a barrier and thus essentially blocking the flow of water from hot water cavity  364  to cold water cavity  362 . In this first position ( FIG. 4 a   ) valve assembly  370  is at ambient temperature and pin  378  is maximally retracted in thermostatic working element  372 . In this first position, valve  374  is blocking hot water cavity  364  thus blocking water flow passage between hot water cavity  364  and cold water cavity  362  and thus preventing flow of water from hot water cavity  364  to cold water cavity  362 . In this first position, a void  382  remains between thermostatic working element  372  and main body  352  allowing room for valve assembly  370  travel to second position. 
         [0106]    Second position ( FIG. 4 b   ) of water saving unit  350  occurs after the activator interface  376  is shifted to its second position. In the second position of water saving unit  350 , thermostatic working element  372  is in a first state (as shown in  FIGS. 5 a - b   ). 
         [0107]    The second position may be activated by the user, effectively allowing the user to decide when he requests warm water. In one embodiment, the activator interface  376  may be a button, and it is shifted to its second position by pressing. When activator interface  376  is shifted to its second position, water flow passage between hot water cavity  364  to cold water cavity  362  is obtained. When activator interface  376  is shifted to its second position, activator interface  376  is pushed towards the center of main body  352 , valve  374  shifts towards void  382  (releasing locked air from vent  384 ) and occupying it. This shift of valve  374  also connects hot water cavity  364  (through opening  386 ) and cold water cavity  362  (through opening  388 ) through cavity  390  located essentially between thermostatic working element  372  and valve body  374  allowing water flow passage between hot water cavity  364  to cold water cavity  362 . 
         [0108]    Since the water pressure in the hot water supply line is greater than the water pressure in the cold water supply line, cold water (not yet warmed) from the hot water cavity  364  flows into the cold water cavity  362  (and on to through port  328  of faucet base  320  and to the cold water supply line). While the cold water flows from the hot water supply line to the cold water supply line, the cold water, in the hot water supply line, is replaced by warmer water. The term “cold water” include, according to some embodiments, water originated from the hot water supply line, which were cooled during a period of time (for example to ambient temperature). As the flow of water continues from hot water cavity  364  flows into the cold water cavity  362  the temperature of the flowing water increases as heated water arrives from the hot water supply line. The increased temperature of the water heats its surrounding including thermostatic working element  372  and water saving unit  350  is shifted into its third position ( FIG. 4 c   ), in which thermostatic working element  372  is in its first state (as shown in  FIGS. 5 a - b   ). 
         [0109]    As a result of heating of thermostatic working element  372 , pin  378  is extracted out from working element  372  and pushes against valve  374  which in turn pushes valve  374  outwardly towards the periphery of main body  352 . When valve  374  is pushed outwardly towards the periphery of main body  352 , valve  374  blocks hot water cavity  364  thus blocking water flow passage between hot water cavity  364  and cold water cavity  362 . In addition, when valve  374  is pushed outwardly towards the periphery of main body  352 , a bottom end of thermostatic working element  372  (the end opposing to the end which accommodates pin  378 ) is presses through bottom opening  392  in valve body  374  and into void  382 . Further, when valve  374  is pushed outwardly towards the periphery of main body  352  activator interface  376  is pushed out from main body  352 . When activator interface  376  is pushed out from main body  352 , activator  354  is also pushed out from water saving unit  350  providing indication to the user that faucet  400  is ready to provide hot water. 
         [0110]    The third position of water saving unit  350  is maintained until the temperature of the water in cavity  390  decreases, cooling thermostatic working element  372 , allowing pin  378  to be retracted back into thermostatic working element  372  by the stretching of spring  380 . Thus water saving unit  350  is shifted back into its first position ( FIG. 4 a   ). 
         [0111]    In one of the embodiments seals  394 , such as a rubber O-rings, are located between main body  352  and valve assembly  370 , for effectively blocking water flow passage between hot water cavity  364  and cold water cavity  362  when the saving unit  350  is in first and third positions. 
         [0112]    While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the invention or exceeding the scope of claims.