Abstract:
A water control fixture includes a fixture body in fluid communication with a pressurized supply of hot water and a pressurized supply of cold water. The fixture body interconnects the supply of hot water and the supply of cold water. The fixture body has a spout outlet configured to dispense water from the fixture body. At least one operating valve is coupled to the fixture body for controlling a flow of water to the spout outlet. A bypass valve is disposed in the fixture body for controlling a recirculating flow of water through the fixture body. The bypass valve blocks and permits recirculating flow from the supply of hot water to the supply of cold water based on a temperature of the water.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application having Ser. No. 13/313084, filed Dec. 7, 2011, titled “WATER CONTROL FIXTURE HAVING BYPASS VALVE”, which is a continuation of U.S. patent application Ser. No. 12/643616 filed Dec. 21, 2008, issued as U.S. Pat. No. 8,091,793 issued Jan. 10, 2012, which is a continuation of U.S. patent application Ser. No. 11/827926, filed Jul. 12, 2007, issued as U.S. Pat. No. 7,648,078 issued Jan. 19, 2010, which is a continuation of U.S. patent application Ser. No. 11/173,572, filed Jul. 1, 2005, issued as U.S. Pat. No. 7,287,707 issued Oct. 30, 2007, which is a continuation of U.S. patent application Ser. No. 10/006,970, filed Dec. 4, 2001, issued as U.S. Pat. No. 6,929,187 on Aug. 16, 2005, which patent is a continuation-in-part of U.S. patent application Ser. No. 09/697,520 filed Oct. 25, 2000, issued as U.S. Pat. No. 6,536,464 issued Mar. 25, 2003, and claimed priority to U.S. Provisional Application No. 60/251,122 filed Dec. 5, 2000, each of which are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to faucets and bypass valves for use in home or industrial water distribution systems that supply water to various fixtures at different temperatures through different pipes. More particularly, the present invention relates to faucets having bypass valves that are thermostatically controlled so as to automatically bypass water that is not at the desired temperature for use at the fixture. Even more particular, the present invention relates to faucets having an integral thermostatically controlled bypass valve. 
         [0003]    Home and industrial water distribution systems distribute water to various fixtures, including sinks, bathtubs, showers, dishwashers and washing machines, that are located throughout the house or industrial building. The typical water distribution system brings water in from an external source, such as a city main water line or a private water well, to the internal water distribution piping system. The water from the external source is typically either at a cold or cool temperature. One segment of the piping system takes this incoming cold water and distributes it to the various cold water connections located at the fixture where it will be used (i.e., the cold water side of the faucet at the kitchen sink). Another segment of the piping system delivers the incoming cold water to a water heater which heats the water to the desired temperature and distributes it to the various hot water connections where it will be used (i.e., the hot water side of the kitchen faucet). At the fixture, cold and hot water either flow through separate hot and cold water control valves that are independently operated to control the temperature of the water into the fixture by controlling the flow rate of water from the valves or the water is mixed at a single valve that selectively controls the desired temperature flowing into the fixture. 
         [0004]    A well known problem common to most home and industrial water distribution systems is that hot water is not always readily available at the hot water side of the fixture when it is desired. This problem is particularly acute in water use fixtures that are located a distance from the hot water heater or in systems with poorly insulated pipes. When the hot water side of these fixtures is left closed for some time (i.e., overnight), the hot water in the hot water segment of the piping system sits in the pipes and cools. As a result, the temperature of the water between the hot water heater and the fixture lowers until it becomes cold or at least tepid. When opened again, it is not at all uncommon for the hot water side of such a fixture to supply cold water through the hot water valve when it is first opened and for some time thereafter. At the sink, bathtub or shower fixture located away from the water heater, the person desiring to use the fixture will either have to use cold or tepid water instead of hot water or wait for the distribution system to supply hot water through the open hot water valve. Most users have learned that to obtain the desired hot water, the hot water valve must be opened and left open for some time so that the cool water in the hot water side of the piping system will flow out ahead of the hot water. For certain fixtures, such as dishwashers and washing machines, there typically is no method of “draining” away the cold or tepid water in the hot water pipes prior to utilizing the water in the fixture. 
         [0005]    The inability to have hot water at the hot water side of the fixture when it is desired creates a number of problems. One problem is having to utilize cold or tepid water when hot water is desired. This is a particular problem for the dishwasher and washing machine fixtures in that hot water is often desired for improved operation of those fixtures. As is well known, certain dirty dishes and clothes are much easier to clean in hot water as opposed to cold or tepid water. Even in those fixtures where the person can let the cold or tepid water flow out of the fixture until it reaches the desired warm or hot temperature, there are certain problems associated with such a solution. One such problem is the waste of water that flows out of the fixture through the drain and, typically, to the sewage system. This good and clean water is wasted (resulting in unnecessary water treatment after flowing through the sewage system). This waste of water is compounded when the person is inattentitive and hot water begins flowing down the drain and to the sewage system. Yet another problem associated with the inability to have hot water at the hot water valve when needed is the waste of time for the person who must wait for the water to reach the desired temperature. 
         [0006]    The use of bypass valves and/or water recirculation systems in home or industrial water distribution systems to overcome the problems described above have been known for some time. The objective of the bypass valve or recirculation system is to avoid supplying cold or tepid water at the hot water side of the piping system. U.S. Pat. No. 2,842,155 to Peters describes a thermostatically controlled water bypass valve, shown as  FIG. 2  therein, that connects at or near the fixture located away from the water heater. In his patent, the inventor discusses the lack of hot water problem and describes a number of prior art attempts to solve the problem. The bypass valve in this patent comprises a cylindrical housing having threaded ends that connect to the hot and cold water piping at the fixture so as to interconnect these piping segments. Inside the housing at the hot water side is a temperature responsive element having a valve ball at one end that can sealably abut a valve seat. The temperature responsive element is a metallic bellows that extends when it is heated to close the valve ball against the valve seat and contracts when cooled to allow water to flow from the hot side to the cold side of the piping system when both the hot and cold water valves are closed. Inside the housing at the cold water side is a dual action check valve that prevents cold water from flowing to the hot water side of the piping system when the hot water valve or the cold water valve is open. An alternative embodiment of the Peters&#39; invention shows the use of a spiral temperature responsive element having a finger portion that moves left or right to close or open the valve between the hot and cold water piping segments. Although the invention described in the Peters&#39; patent relies on gravity or convection flow, similar systems utilizing pumps to cause a positive circulation are increasingly known. These pumps are typically placed in the hot water line in close proximity to the faucet where “instant” hot water is desired. 
         [0007]    U.S. Pat. No. 5,623,990 to Pirkle describes a temperature-controlled water delivery system for use with showers and eye-wash apparatuses that utilize a pair of temperature responsive valves, shown as  FIGS. 2 and 5  therein. These valves utilize thermally responsive wax actuators that push valve elements against springs to open or close the valves to allow fluid of certain temperatures to pass. U.S. Pat. No. 5,209,401 to Fiedrich describes a diverting valve for hydronic heating systems, best shown in  FIGS. 3 through 5 , that is used in conjunction with a thermostatic control head having a sensor bulb to detect the temperature of the supply water. U.S. Pat. No. 5,119,988 also to Fiedrich describes a three-way modulating diverting valve, shown as  FIG. 6 . A non-electric, thermostatic, automatic controller provides the force for the modulation of the valve stem against the spring. U.S. Pat. No. 5,287,570 to Peterson et al. discloses the use of a bypass valve located below a sink to divert cold water from the hot water faucet to the sewer or a water reservoir. As discussed with regard to  FIG. 5 , the bypass valve is used in conjunction with a separate temperature sensor. 
         [0008]    A recirculating system for domestic and industrial hot water heating utilizing a bypass valve is disclosed in U.S. Pat. No. 5,572,985 to Benham. This system utilizes a circulating pump in the return line to the water heater and a temperature responsive or thermostatically actuated bypass valve disposed between the circulating pump and the hot water heater to maintain a return flow temperature at a level below that at the outlet from the water heater. The bypass valve, shown in  FIG. 2 , utilizes a thermostatic actuator that extends or retracts its stem portion, having a valve member at its end, to seat or unseat the valve. When the fluid temperature reaches the desired level, the valve is unseated so that fluid that normally circulates through the return line of the system is bypassed through the circulating pump. 
         [0009]    Despite the devices and systems set forth above, many people still have problems with obtaining hot water at the hot water side of fixtures located away from the hot water heater or other source of hot water. Boosted, thermally actuated valve systems having valves that are directly operated by a thermal actuator (such as a wax filled cartridge) tend not to have any toggle action. Instead, after a few on-off cycles, the valves tend to just throttle the flow until the water reaches an equilibrium temperature, at which time the valve stays slightly cracked open. While this meets the primary function of keeping the water at a remote faucet hot, leaving the valve in a slightly open condition does present two problems. First, the lack of toggle action can result in lime being more likely to build up on the actuator because it is constantly extended. Second, the open valve constantly bleeds a small amount of hot or almost hot water into the cold water piping, thereby keeping the faucet end of the cold water pipe substantially warm. If truly cold water is desired (i.e., for brushing teeth, drinking, or making cold beverages), then some water must be wasted from the cold water faucet to drain out the warm water. If the bypass valve is equipped with a spring loaded check valve to prevent siphoning of cold water into the hot water side when only the hot water faucet is open, then the very small flow allowed through the throttled-down valve may cause chattering of the spring loaded check valve. The chattering can be avoided by using a free floating or non-spring loaded check valve. It is also detrimental to have any noticeable crossover flow (siphoning) from hot to cold or cold to hot with any combination of faucet positions, water temperatures, or pump operation. 
         [0010]    U.S. Pat. No. 6,536,464 the disclosure of which is incorporated herein as fully set forth and having some of the same inventors and the same assignee as the present invention, describes an under-the-sink thermostatically controlled bypass valve and water circulating system with the bypass valve placed at or near a fixture (i.e., under the sink) to automatically bypass cold or tepid water away from the hot water side of the fixture until the temperature of the water reaches the desired level. The system described in U.S. Pat. No. 6,536,464 includes a single small circulating pump that is placed between the water heater and the first branching in the hot water supply line which supplies the fixture having a bypass valve so as to pressurize the hot water piping system and facilitate bypassing of the cold or tepid water. 
         [0011]    The public is accustomed to purchasing faucets for lavatories, bathtubs, showers, kitchen sinks and etc. that can be readily repaired, usually by removing a top-mounted handle and bonnet, and replacing a faucet washer or other seal or seat. In recent designs, the sealing action occurs within a replaceable cartridge, which can be easily replaced by the home repair person. None of the known prior art devices include the use of an integral thermostatically controlled bypass valve to bypass water as described above. However, for a thermal bypass valve to be included in a faucet, it is necessary that it meet the same expectation for ease of repair as the standard faucet. There are several advantages to location of the thermal bypass valve within the faucet itself and being accessible from the top, which include: (1) elimination of the clutter resulting from extra hoses located below the sink and the need to do plumbing and maintenance below the sink; (2) elimination of the under-the-sink hoses, which by their very presence add potential leak paths at each end of each hose; (3) a new feature that a faucet manufacturer can use to define its top-of-the-line faucet, which can stimulate sales to those customers who like to have the latest in convenience; and (4) the bypass valve can be serviced by the home repair person or, if desired, professional plumber in a standing position in a manner which is already learned from the maintenance of existing design faucets. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0012]    In an exemplary embodiment, a water control fixture is provided including a housing having a plurality of ports defining a hot water inlet port, a bypass port, and a fixture outlet port, wherein water is dispensed via the fixture outlet port. At least one operating valve is disposed in the housing for controlling a flow of water from the hot water inlet port to the fixture outlet port. A bypass valve is disposed in the housing for controlling a flow of water from the hot water inlet port to the bypass port. 
         [0013]    Optionally, the plurality of ports includes a cold water port configured to be in fluid communication with a cold water supply line, wherein the at least one operating valve may control a flow of water from the cold water port to the fixture outlet port. The bypass valve may control a flow of water from the hot water inlet port to the cold water port. Optionally, the bypass valve may opens to permit a flow of water from the hot water inlet port to the bypass port based on an activation condition. The bypass valve may be thermostatically controlled and may control the flow of water from the hot water inlet port to the bypass port until the temperature of the water at the hot water inlet port is at a preset level. Optionally, the bypass port may be configured to be in fluid communication with one of a dedicated return line and a cold water supply line. Optionally, the housing may represent a faucet and include at least one handle provided on the housing, wherein the handle is joined to the at least one operating valve to control the flow of water from the hot water inlet port and the fixture outlet port. 
         [0014]    In another embodiment, a water control fixture is provided including a housing having a plurality of ports defining a hot water inlet port, a bypass port, and a fixture outlet port, wherein water is dispensed via the fixture outlet port. At least one handle is attached to the housing for controlling the flow of water from the hot water inlet port to the fixture outlet port. A bypass member is disposed in the housing for controlling a flow of water from the hot water inlet port to the bypass port. 
         [0015]    In a further embodiment, a water control fixture is provided including a housing having a chamber and a plurality of ports in fluid communication with the chamber. The plurality of ports define a hot water inlet port, a bypass port, and a fixture outlet port, wherein water is dispensed via the fixture outlet port. A flow control unit is received within the chamber and is configured to be selectively positioned in fluid communication with the plurality of ports for controlling the flow of water from the hot water inlet port to the fixture outlet port and for controlling the flow of water from the hot water inlet port to the bypass port. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows a water distribution system that utilizes a water control fixture (faucet) having a thermostatically controlled bypass valve of the present invention; 
           [0017]      FIG. 2  is a side view of the preferred thermally sensitive actuating element, shown in its unmodified condition, for use in the bypass valve of the present invention; 
           [0018]      FIG. 3  is a front view of a typical fixture body for a single handle faucet; 
           [0019]      FIG. 4  is a side view of the single handle faucet in  FIG. 3 ; 
           [0020]      FIG. 5  is a top view of the faucet body housing for the faucet of  FIG. 3 ; 
           [0021]      FIG. 6  is a side cross-sectional view of the faucet body housing for the faucet of  FIG. 3 ; 
           [0022]      FIG. 7  is a bottom view of the faucet body housing of the faucet of  FIG. 3 ; 
           [0023]      FIG. 8  is a sectional view of a bypass valve cartridge body for use with the present invention; 
           [0024]      FIG. 9  is a sectional view of the bypass valve cartridge body taken at 90 degrees to  FIG. 8 ; 
           [0025]      FIG. 10  is a sectional view of the bypass valve cartridge body of  FIG. 8  with a bypass valve and other components place therein; 
           [0026]      FIG. 11  is a cross-sectional view of the side of a shower faucet that utilizes a cartridge insert (not shown) for controlling the flow of water through the faucet showing the placement of a bypass valve therein; 
           [0027]      FIG. 12  is a cross-sectional view of the side of a modified ball control mechanism for use in single handle faucets; 
           [0028]      FIG. 13  is a top view of the ball of  FIG. 12 ; 
           [0029]      FIG. 14  is a side view of the ball of  FIG. 12 ; 
           [0030]      FIG. 15  is a cross sectional view of modified replaceable cylindrical valving cartridge used in some faucets as adapted for the present invention; 
           [0031]      FIG. 16  is a side view of a valve member used with dual handle, single spout faucets; 
           [0032]      FIG. 17  is side cross-sectional view of the upper half of a cartridge placed in the valve member of  FIG. 16 ; 
           [0033]      FIG. 18  is chart showing the operational characteristics of the bypass valve of the present invention when in use with a water distribution system; and 
           [0034]      FIG. 19  is a side cross-sectional view of a modified thermal actuator showing modifications to reduce problems with lime buildup. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    With reference to the figures where like elements have been given like numerical designations to facilitate the reader&#39;s understanding of the present invention, the preferred embodiments of the present invention are set forth below. The enclosed figures and drawings are illustrative of the preferred embodiments and represent a preferred way of configuring the present invention. Although specific components, materials, configurations and uses are illustrated, it should be understood that a number of variations to the components and to the configuration of those components described herein and in the accompanying figures can be made without changing the scope and function of the invention set forth herein. 
         [0036]    In the accompanying drawings of the various preferred embodiments of a water control fixture of the present invention, the water control fixture is shown as faucet  10 . However, other water control fixtures may be adaptable to the thermal bypass valve features described herein (i.e., solenoid valve used on home laundry washing machines). A typical water distribution system  12  utilizing faucet  10  of the present invention is illustrated in  FIG. 1 . The water distribution system  12  typically comprises a supply of cold water  14 , such as from a city main or water well, that supplies cold water directly to faucet  10  through cold water line  16  and water to hot water heater  18  so that it may heat the water and supply hot water to faucet  10  through hot water line  20 . Cold water line  16  connects to faucet  10  through cold water inlet  22  and hot water line  20  connects to faucet  10  through hot water inlet  24 , as explained in more detail below. 
         [0037]    The preferred system  12  of the present invention utilizes a small circulating pump  26  of the type used in residential hot water space heating. A very low flow and low head pump is desirable because a larger (i.e., higher head/higher flow) pump mounted at the typical domestic water heater  18  tends to be noisy. This annoying noise is often transmitted by the water pipes throughout the house. In addition, if the shower (as an example) is already in use when pump  26  turns on, whether the first start or a later cyclic turn-on, the sudden pressure boost in the hot water line  20  from a larger pump can result in an uncomfortable and possibly near-scalding temperature rise in the water at the shower head or other fixture in use. The smaller boost of a “small” pump (i.e., one with a very steep flow-head curve) will result in only a very small and less noticeable increase in shower temperature. In the preferred embodiment, the single, small pump  26  needs to provide only a flow of approximately 0.3 gpm at 1.0 psi pressure. In accordance with pump affinity laws, such a “small” pump requires a very small impeller or low shaft speed. The inventors have found that use of a very small impeller or low shaft speed also precludes formation of an air bubble in the eye of the impeller, which bubble may be a major cause of noise. Such a small steep curve pump may, however, constitute a significant pressure drop in the hot water line  20  when several fixture taps are opened simultaneously (such as a bathtub and the kitchen sink). To avoid reduced flow in those installations having a relatively low volume pump, a check valve  28  can be plumbed in parallel with pump  26  or incorporated within the pump housing, to pass a flow rate exceeding the pump&#39;s capacity around pump  26 . When pump  26  is powered and flow demand is low, check valve  28  prevents the boosted flow from re-circulating back to its own inlet. With check valve  28  plumbed around pump  26 , it is advantageous to place an orifice  30  in the pump discharge to provide a simple manner to achieve the desired very steep flow-head curve from available stock pump designs. A single pump  26  located at or near the water heater  18  in its discharge piping will boost the pressure in the hot water pipes somewhat above that in the cold water pipes (i.e., perhaps one to three feet of boost). With this arrangement only one pump  26  per plumbing system (i.e., per water heater  18 ) is required with any reasonable number of remote faucets  10  (i.e., the typical number used in residences) equipped with bypass valves. This is in contrast to those systems that require multiple pumps, such as a pump at each fixture where bypassing is desired. 
         [0038]    If desired, pump  26  can operate twenty-four hours a day, with most of the time in the no flow mode. However, this is unnecessary and wasteful of electricity. Alternatively, pump  26  can have a timer  32  to turn on the pump  26  daily at one or more times during the day just before those occasions when hot water is usually needed the most (for instance for morning showers, evening cooking, etc.) and be set to operate continuously for the period during which hot water is usually desired. This still could be unnecessary and wasteful of electricity. Another alternative is to have the timer  32  cycle pump  26  on and off regularly during the period when hot water is in most demand. The “on” cycles should be of sufficient duration to bring hot water to all remote fixtures  10  that are equipped with a bypass valve, and the “off period” would be set to approximate the usual time it takes the water in the lines to cool-down to minimum acceptable temperature. Yet another alternative is to equip pump  26  with a normally closed flow switch  34  sized to detect significant flows only (i.e., those flows that are much larger than the bypass valve flows), such as a shower flowing. For safety purposes, the use of such a switch  34  is basically required if a cyclic timer  32  is used. The switch  34  can be wired in series with the motor in pump  26 . If the switch  34  indicates an existing flow at the moment the timer calls for pump  26  to be on, the open flow switch  34  will prevent the motor from starting, thereby avoiding a sudden increase in water temperature at the fixture  10  (i.e., particularly if it is a shower) being utilized. The use of such switch  34  accomplishes several useful objectives, including reducing electrical power usage and extending pump life if hot water is already flowing and there is no need for the pump to operate, avoiding a sudden temperature rise and the likelihood of scalding that could result from the pump boost if water is being drawn from a “mixing” valve (such as a shower or single handle faucet) and allowing use of a “large” pump (now that the danger of scalding is eliminated) with its desirable low pressure drop at high faucet flows, thereby eliminating the need for the parallel check valve  28  required with a “small” pump. 
         [0039]    By using a time-of-day control timer  32 , pump  26  operates to maintain “instant hot water” only during periods of the day when it is commonly desired. During the off-cycle times, the plumbing system  12  operates just as if the faucet  10  having bypass valves and pump  26  were not in place. This saves electrical power usage from pump operation and, more importantly, avoids the periodic introduction of hot water into relatively un-insulated pipes during the off-hours, thereby saving the cost of repeatedly reheating this water. The time-of-day control also avoids considerable wear and tear on pump  26  and the bypass valve in faucet  10 . Considerable additional benefits are gained by using a cyclic timer  32 , with or without the time-of-day control. In addition to saving more electricity, if a leaky bypass valve or one not having toggle action is used, there will be no circulating leakage while the pump  26  is cycled off, even if the valve fails to shut off completely. Therefore, a simple (i.e., one not necessarily leak tight) valve may suffice in less demanding applications. Having the leakage reduced to just intermittent leakage will result in reduced warming of the cold water line  16  and less reheating of “leaking” re-circulated water. 
         [0040]    The bypass valve assemblies  36  utilized with the present invention have a thermally sensitive actuating element  38 , an example of which is shown in  FIG. 2 , for thermostatically controlling bypass valve  36 . Actuating element  38  is preferably of the wax filled cartridge type, also referred to as wax motors, having an integral poppet rod member  40 , as best shown in  FIG. 2 . Rod member  40  comprises poppet  42  attached to piston  44  with an intermediate flange  46  thereon. The end of poppet  42  is configured to seat directly against a valve seat or move a shuttle (i.e., spool or sleeve valves) so as to close a passage. These thermostatic control elements  38  are well known in the art and are commercially available from several suppliers, such as Caltherm of Bloomfield Hills, Mich. The body  48  of actuating element  38  has a section  50  of increased diameter, having a first side  52  and second side  54 , to seat against a shoulder or like element in a valve body. Piston  44  of rod member  40  interconnects poppet  42  with actuator body  48 . Actuating element  38  operates in a conventional and well known manner. Briefly, actuating element  38  comprises a blend of waxes or a mixture of wax(es) and metal powder (such as copper powder) enclosed in actuator body  48  by means of a membrane made of elastomer or the like. Upon heating the wax or wax with copper powder mixture expands, thereby pushing piston  44  and poppet  42  of rod member  40  in an outward direction. Upon cooling, the wax or wax/copper powder mixture contracts and rod member  40  is pushed inward by a bias spring until flange  46  contacts actuator body  48  at actuator seat  56 . Although other types of thermal actuators, such as bimetallic springs and memory alloys (i.e., Nitinol and the like) can be utilized in the present invention, the wax filled cartridge type is preferred because the wax can be formulated to change from the solidus to the liquid state at a particular desired temperature. The rate of expansion with respect to temperature at this change of state is many times higher, resulting in almost snap action of the wax actuating element  38 . The temperature set point is equal to the preset value, such as 97 degrees Fahrenheit, desired for the hot water. This is a “sudden” large physical motion over a small temperature change. As stated above, this movement is reacted by a bias spring that returns rod member  40  as the temperature falls. 
         [0041]    Because the bypass valve  36  has little or no independent “toggle action,” after a few cycles of opening and closing, the valve tends to reach an equilibrium with the plumbing system, whereby the bypass valve  36  stays slightly cracked open, passing just enough hot water to maintain the temperature constantly at its setting. In particular plumbing systems and at certain ambient conditions, this flow is just under that required to maintain a spring loaded check valve cracked continuously open. In such a situation, the check valve chatters with an annoying buzzing sound. To avoid this occurrence, the spring may be removed from the check valve, leaving the poppet free floating. In the event that the hot water is turned full on at a time when the bypass valve  36  is open, thereby lowering the pressure in the hot water line  20 , and so inducing flow from the cold water line  16  through the open bypass valve  36  to the hot side, the free floating poppet will quickly close. There is no necessity for a spring to keep this check valve closed prior to the reversal in pressures. 
         [0042]    Although not entirely demonstrated in early tests, it is believed that beneficial “toggle” action can be achieved with a bypass valve  36  of very simple mechanical design. If the motion of the thermal actuator  38  is made to lag behind the temperature change of the water surrounding it by placing suitable insulation around the actuator  38  or by partially isolating it from the water, then instead of slowly closing only to reach equilibrium at a low flow without reaching shutoff, the water temperature will rise above the extending temperature of the insulated actuator  38  as the valve approaches shutoff, and the piston  44  will then continue to extend as the internal temperature of the actuator  38  catches up to its higher surrounding temperature, closing the valve  36  completely. It is also believed that an insulated actuator  38  will be slow opening, its motion lagging behind the temperature of the surrounding cooling-off water from which it is insulated. When actuating element  38  finally begins to open the valve  36  and allow flow, the resulting rising temperature of the surrounding water will again, due to the insulation, not immediately affect it, allowing the bypass valve  36  to stay open longer for a complete cycle of temperature rise. Such an “insulated” effect may also be accomplished by use of a wax mix that is inherently slower, such as one with less powdered copper or other thermally conductive filler. An actuator  38  to be installed with insulation can be manufactured with a somewhat lower set point temperature to make up for the lag, allowing whatever valve  36  closing temperature desired. 
         [0043]    An additional benefit of utilizing pump  26  in system  12  is that shut-off of a toggle action valve upon attainment of the desired temperature is enhanced by the differential pressure an operating pump  26  provides. If pump  26  continues to run as the water at the faucet  10  cools down, the pump-produced differential pressure works against re-opening a poppet type bypass valve  36  in faucet  10 . If pump  26  operates cyclically, powered only a little longer than necessary to get hot water to faucet  10 , it will be “off” before the water at valve  36  cools down. When the minimum temperature is reached, the thermal actuator  38  will retract, allowing the bias spring to open valve  36  without having to fight a pump-produced differential pressure. By-pass flow will begin with the next pump “on” cycle. An additional benefit to the use of either a time-of-day or cyclic timer  32  is that it improves the operating life of thermal actuator  38 . Because use of either timer  32  causes cyclic temperature changes in valve  36  (as opposed to maintaining an equilibrium setting wherein temperature is constant and the actuator  38  barely moves), there is frequent, substantial motion of the piston  44  in thermal actuator  38 . This exercising of actuator  38  tends to prevent the build-up of hard water deposits and corrosion on the cylindrical surface of actuator piston  44  and face of poppet  42 , which deposits could render the valve  36  inoperable. 
         [0044]    Also inside valve  36  can be an over-travel spring (not shown) disposed between the first side  52  of the actuator body  48  and a stop located inside valve  36  to prevent damage to a fully restrained actuator  38  if it were heated above the bypass valve&#39;s maximum operating temperature and to hold the actuator  38  in place during operation without concern for normal tolerance. Use of an over-travel spring, which is not necessary for spool-type valves, allows movement of the actuator body  48  away from the seated poppet  42  in the event that temperature rises substantially after the poppet  42  contacts its seat. Without this relief, the expanding wax could distort its copper can, destroying the calibrated set point. The over-travel spring also holds the bias spring, rod member  40  and actuator body  48  in place without the need to adjust for the stack-up of axial tolerances. Alternatively, actuator  38  can be fixedly placed inside valve  36  by various mechanisms known in the art, including adhesives and the like. Over-travel spring, if used, can be held in place by various internal configurations commonly known in the art, such as a molded seat. 
         [0045]    As there are a great many configurations and brands of faucets  10 , there are several different preferred designs of bypass valve  36  placement and arrangement to accommodate these many faucet configurations. For purposes of illustrating the present invention, various specific examples are set forth below. The following examples are representative of the types of uses to which the integral or in-faucet bypass valve  36  is suitable. The examples are for illustrative purposes only and are not intended to restrict the invention to particular uses, sizes or materials used in the examples. 
         [0046]    For instance, there are several basic types of faucet assemblies, including those that have a single handle faucet assembly that mixes the hot and cold water and delivers a flow of water out the single spout based on the user&#39;s movement of the faucet&#39;s valve assembly. Another common type of faucet assembly is the dual handle, single spout faucet assembly that has separate handles for the hot and cold water. As with the single handle assembly, the hot and cold water are mixed prior to the spout based on the user&#39;s selection of the amount of flow of hot and/or cold water. A third, older arrangement is the use of completely separate faucets for hot and cold water. Although the different manufacturers of faucets may utilize different arrangements of valving components, different valving mechanisms and/or different valves to water supply line connections, the bypass valve system of the present invention is adaptable to all such known configurations. As set forth below, the primary selection in the use of the bypass faucet assembly of the present invention is whether to place the bypass valve in a stationary portion of the faucet, such as the hot water piping leading to the faucet or in a housing or block portion of the faucet, or to place the bypass valve in the moveable valving of the faucet. Selection of which location to place the bypass valve assembly will often be dictated by economics, preferences, limitations on the amount of space available, the current design of the faucet and/or the willingness to change. 
       Example 1  
     Single Handle Faucets w/Bypass Valve in Stationary Block 
       [0047]    As is well known, single handle faucets, an example of which is shown as fixture body  60 , faucet  10  without its decorative covering, in  FIGS. 3 and 4 , have both hot  24  and cold  22  water inlets connected to a housing or block  62 . Various internal valving means, such as pivoting and rotating ball  64 , selectively and adjustably control the volume and temperature of the flow of water by connecting the hot  20  and cold  16  lines, through hot and cold conduits  66  and  68  respectively (as shown in  FIGS. 5 and 7 ), to a single outlet spout  70  through spout outlet  72 . In such designs, the thermal bypass valve  36  is preferably assembled into an easily replaceable cartridge  74 , shown best in  FIGS. 8 ,  9  and  10 , that can be located within the hot water conduit  66  of fixture body  60  (if the design provides such access) or in an added cavity  76  placed between and connected to the hot  24  and cold  22  inlets, as shown in  FIG. 7 . In either case, the bypass valve  36  senses and is controlled by the temperature of the “hot” water in the fixture body  60 . When the “hot” water is cooled off due to long disuse, the bypass valve  36  will open, providing a conduit between the hot  24  and cold  22  inlets. If the hot water line pump  26  is then turned on, the boosted pressure in the hot water line  20  will produce flow through the open bypass valve  36 , bringing “hot” water to the fixture body  60 . In the above-mentioned arrangements, the flow of water from both hot  20  and cold  16  lines remains unimpeded due to the previously mentioned internal valving arrangement of the fixture body  60 . The flow from the hot line  20  through the bypass valve cartridge  74  to the cold line  16  is provided through molded or cast passages or cross-drilled holes, discussed below. 
         [0048]    The single handle faucet body  60  with spherical ball valving means  64 , shown in  FIGS. 3 and 4 , is a good example of a faucet design that can be easily and economically re-designed to include a bypass valve cartridge  74  in the stationary housing  62 . Use of this approach requires a new fixture body  60  to be installed, with a top-accessible, suitably sized cavity  76  to hold the bypass cartridge  74  and connect conduits  66  and  68  built into the fixture body  60  to accommodate the bypassed flow from the hot  20  to the cold  16  lines.  FIGS. 5 through 7  show a modified and lengthened version of a Delta housing  62  that is used with the standard Delta faucet outer housing. The portion  78  above line AA (i.e., to the left of in  FIG. 6 ) it is essentially an original Delta housing, with the addition of bore  76 . Below AA (i.e., to the right of in  FIG. 6 ) is extension  80 . In the preferred use of the present invention, these sections  78  and  80  would be made in a single, integral housing  62 . Cavity  76  and the drilled and plugged cross passages  82  and  84  are added, and the top bore  86  is extended inward if and as much as is needed to accommodate any necessary devices, such as a ring or washer to hold cartridge assembly  74  in place in cavity  76 . Drilled passage  82  connects the cold water supply to cavity  76  near its top and drilled passage  84  connects the hot water line  20  to cavity  76  near its bottom. 
         [0049]      FIGS. 8 and 9  show the bypass valve cartridge  74 , without its internal components, that is designed and configured to fit in cavity  76 .  FIG. 10  shows the components, including thermal actuator  88 , assembled together as they would fit into cavity  76 . The thermal actuator  88  is a modified version of the actuator  38  that is used in U.S. Pat. No. 6,536,464 and shown in  FIG. 2  herein. Water from hot water line  20  is carried through drilled hole  84  to the lower end of cavity  76  and flows up around and through the cartridge  74  to and through the open valve seat  90  (poppet  42  is shown closed into against O-ring  92  forming seat  90  in  FIG. 10 ) into the check valve chamber  94  housing check valve  96  and out through the cross drilled hole  98  into an annulus  100  on the cartridge  74 . From annulus  100 , between O-rings  102  and  104 , the water flows through drilled passage  82  to the cold water supply. When sufficient water has flowed through the bypass valve  36  to exhaust the cooled-off water in the hot water supply line  20  and bring hot water to the bypass valve  36 , the thermal actuator  88  will cause piston  44  to extend, forcing poppet  42  into seat  90  to close off the flow. The seat O-ring  92  is held in place by spring  106 , which doubles as the bias or poppet return spring. In the preferred embodiment, thermal actuator  88  is held in place by a snap fit into the split cartridge  74 , which is designed to be easily moldable. The check valve  96  is included to prevent flow of cold water into the hot side when the hot water is turned full on in the system, or the equivalent usage of hot water, resulting in a lowered pressure on the hot side. The cartridge  74  can be held down in cavity  76  by a brass ring, or the like, which is in turn held down by the screw-on bonnet, which also captures the existing ball valving assembly  64 . 
         [0050]    Another example of a single handle water control fixture is shown as  110  in  FIG. 11 . This fixture  110  is a modified Moen shower valve that comprises a rear housing  112  attached to the rear  114  of Moen housing  116 . Housing  116  has a hot water inlet port  118  and a cold water inlet port  120  for receiving hot and cold water, respectively, from the hot  20  and cold  16  water lines and a valve cavity  122  for receiving the operating valve (not shown) through valve opening  124 . The operating valve controls the flow of hot and cold water out of the spout associated with valve  110 . Rear housing  112  has a cavity  126  configured to hold cartridge  127  and hot  128  and cold  130  water channels to allow passage of water around valve cavity  126  until the hot water reaches the desired temperature to cause actuator  38  to push piston  44  rearward until poppet  42  engages valve seat  90  to shut-off hot water flow through hot water channel  128 , thereby ending the diversion of “hot” water to the cold water channel  130 . Elastomeric washer shaped diaphragm  125  acts as a check valve to prevent back flow of cold to hot when hot water line pressure is reduced. Conical washer shaped screens  129  filers detritus and other trash from passing water. Screens  129  are self-cleaning due to the high water velocities encountered when the shower valve is running hot water. 
       Example 2  
     Single Handle Faucets w/Bypass Valve in Moveable Valving 
       [0051]    This family of valves may utilize either a moveable perforated hollow spherical ball  64 , as shown in  FIGS. 3 and 4 , or an internally moveable valve cartridge, that have a common internal flow area to selectively and adjustably connect the hot  20  and cold  16  lines to the discharge spout  70 . It is possible to place the same thermal valve system  36  (in a more compact form) inside of a replacement one inch diameter ball  134  for the moveable ball type or inside the replaceable faucet cartridges with internally moveable valving parts. 
         [0052]    The previous simple hollow sphere, now  134  (shown in  FIGS. 12 ,  13  and  14 ), is structurally divided into two separate compartments inside ball body  135 , an outer annular compartment  136 , coaxial with the centerline of the actuating stem  138 , and a cylindrical inner compartment  140 , also coaxial with the centerline of the actuating stem  138 . Passage  162 , connected to annulus  159 , and passage  164 , connected to central bore  157 , are separated by the valving action of the bypass valve  36  installed in compartment  140 . Ball  134  is made in two parts, an upper half  142  and a lower half  144  (relative to the stem  138  which normally extends upward), which screw together for convenience in development work. The thermal actuator  88  is enclosed in the inner compartment  140  is the same as the actuator discussed above, but with a shortened guide length and a cut-off piston  44  with no poppet. The radially squeezed O-ring  146  seals the two halves  142  and  144  of ball  134 , and is held in place by the spring  148 , which also functions as the bias or return spring. The piston  44  is cut off short to conserve space, and bears on the upper end of drilled hole  150 . Unlike the above-mentioned actuators, this piston  44  remains stationary and it&#39;s the thermal actuator body  48  that moves against spring  148  to push the elastomer poppet disc  152 , which doubles as a check valve, against the stationary seat  154  as the valve  134  heats up. 
         [0053]    The two inlet ports on ball body  135 , shown as  156  for the hot water inlet port and  158  for the cold water inlet port on  FIGS. 13 and 14 , selectively and adjustably communicate with the hot  20  and cold  16  lines. The ball discharge port  160  communicates in all ball positions with the faucet spout to discharge water from faucet  10 . Ports  156 ,  158  and  160  are located in exactly the same locations on the ball body  135  as the prior art ball  64  previously. However all three ports are connected within the ball to annular compartment  136  instead of to the entire inner volume of the hollow prior art ball  64 . In the shut-off mode, the hot and cold inlet ball ports  156  and  158 , respectively, of ball  134  are shifted away from the hot  20  and cold  16  lines, as with prior art ball  64 . However, ball  134  includes two added small ports  162  and  164  to the un-perforated spherical surface that previously blocked off the hot  20  and cold  16  lines. Ports  162  and  164  connect the hot  20  and cold  16  lines to the central bore  157  and annulus  159 , which are valved by action of poppet disc  152 . When the ball  134  is cold due to a cooled-off hot water line  20 , the bypass valve  36  opens, allowing communication between the annulus  159  and central bore  157 . With the faucet  10  in the shut-off position, the two added ports  162  and  164  thus allow communication between a cooled-off “hot” line  20  and the cold line  16 , and consequently a flow of water from the boosted “hot” line  20  to the cold line  16 . Positioning slot  165  in ball  134 , also in ball  64 , is used to position ball  134  in the faucet. The bypass action described above is accomplished without change to any part of the faucet  10  except the replaceable valving ball  134 . It is thus very easy to retrofit an existing faucet to the bypass function by simply replacing the existing “standard” design hollow ball  64  with the new ball  134 , as described. 
         [0054]    There are several major advantages to this arrangement. These advantages include: (1) the complete ball  134  is easily replaced to fix a malfunctioning bypass valve  36 ; (2) for retrofit, the original ball  64  can be removed and replaced with the new valve-in-ball  134 . No other changes need be made to the existing faucet  10  (however, a booster pump  26  located near the hot water heater  18  in the hot water line  20  does of course need to be installed). This is particularly advantageous where it would be very difficult or impractical to replace an existing complete faucet valve, such as a shower valve installed behind a tiled wall. 
         [0055]    While the hollow ball  64  of the Delta faucet (and other clone faucets) provides an adequate space in a convenient location for installation of the bypass valve  36 , a miniaturized version of the bypass valve  36  can also be fitted into the replaceable cylindrical valving cartridges of other brands of single handle faucets with an action characterized by oscillating movement about a vertical centerline to adjust water temperature. Such a valving action to control mixing is commonly used in Price-Pfister, Sterling, American Standard, Moen, and Kohler faucets, among others. These faucets use a push-pull or tipping lever action to operate the on-off function within the same (usually) cylindrical cartridge. On some configurations, it is likely that space would have to be made by lengthening these cylindrical faucet cartridges, which would in turn call for a compensating change to the faucet central housing. 
         [0056]      FIG. 15  shows a modification of a widely used Moen designed faucet  200  as an example of a fixture that utilizes a replaceable cylindrical valving cartridge  202 . The modifications to the faucet  200  include adding a hot water bypass valve  36  within the moving valving spool  204  of the Moen design. This valve design is of the type wherein on/off and metering adjustment is accomplished by axial motion of the center spool  204  (off is all the way inward). Hot/cold mixing adjustment is by angular positioning of the center spool  204  when it is wholly or partially pulled out to the on position. The faucet  200  typically has a brass housing  206  connected to the cold water inlet  208  and hot water inlet  210 . A spout connection  212  allows water to exit the fixture  200 .  FIG. 15  shows the spool  204  in its outward or “full on” position (slot  214  axially aligns with spout port  212  and slot  216  axially aligns with cold  208  and hot  210  inlet ports) and angularly rotated so that the hot port  210  is open to slot  216  but cold port  208  is blocked off. 
         [0057]    In the position shown in  FIG. 15 , hot water from port  210  can enter through slot  216  to the interior of tubular spool  204  and proceed through hollow shuttle  218  to slot  214  and exit out spout port  212 . Arrows  220  indicate the length of travel of the spool  204 . Tubular member  222  is a stationary (preexisting) sleeve incorporated within the housing  206  to allow placement and retention of the three elastomer seals  224  to bear against and dynamically seal with spool  204 . It also provides a vent path around its exterior for the space at the “bottom” of the valve  200  to allow axial (piston) motion of spool  204  without encountering hydraulic lock. Spool  204  is shown in a simplified one-piece configuration for clarity. 
         [0058]    The bypass valve  36  components (consisting of bias spring  226 , shuttle  218 , actuator piston  228  and actuator  230 ) are enclosed within the tubular portion of spool  204 . Shuttle  218  is located (floats) between bias spring  226  and actuator  230 . Shuttle  218  has a central cruciform shaped member with an integral elastomer sleeve  232  attached to the four legs of the cruciform. Four axial passages within the sleeve  232  and around the cruciform are thus provided. This elastomer sleeve  232  is in contact with and seals against the inner surface of tubular spool  204 . When thermal actuator  230  is heated to its actuation temperature, it “suddenly” extends piston  228  outward, moving shuttle  218  (to the left in  FIG. 15 ) against bias spring  226 . 
         [0059]    Two bleed holes  234  and  236  are so located through the wall of tubular spool  204  as to line up with hot water inlet  210  and cold water inlet  208 , respectively, when the manually operated spool  204  is pushed all the way into housing  206  (the off position). Further, bleed hole  236  is axially located slightly closer to the bias spring end of spool  204 . O-rings  238  seal spool  204  and retaining clip  240  holds sleeve  222  within housing  206 . 
         [0060]    In  FIG. 15 , the bypass valve  36  components are shown in their “cold” positions. Hot bleed hole  234  is covered by the end of the elastomer sleeve  232  on shuttle  218 , but cold bleed hole  236  is uncovered. With spool  204  pushed all the way in (off position) bleed hole  234  communicates with hot water inlet  210  and boosted hot water pressure communicates through hot bleed hole  234 . this pressure deflects elastomer sleeve  232  inward locally to allow flow from the boosted hot water line  20  (presumably cooled off from a period of disuse) into the interior of tubular spool  204  and out through uncovered cold bleed hole  236 , which by virtue of the spool  204  being in the off position is in communication with cold water inlet  208 . A bypass of cooled off water from the hot water line  20  to the cold water line  16  is thus accomplished. 
         [0061]    When sufficient cooled off water has passed through the valve  200  to bring “hot” water to and through the valve  200 , actuator  230  will be warmed to its actuation temperature and will expand, forcing shuttle  218  against bias spring  226 . This axial movement will result in elastomer sleeve  232  covering cold bleed hole  236 . Boosted hot water pressure internal to sleeve  232  will hold sleeve  232  outward against the inner wall of tubular spool  204 , effectively sealing bleed hole  236 , and stopping the bypass flow until the valve cools down, causing bias spring  226  to force shuttle  218  back against piston  10  into contracting actuator  230 , again opening cold bleed hole  236 . 
         [0062]    The elastomer sleeve  232  has a second function, that of acting as a check valve. When any faucet in the plumbing system is opened, the resulting flow may induce a substantial pressure drop in the associated plumbing line (either hot  20  or cold  16 , depending on which faucet was opened). If a bypass valve  36  is open at such a time, such a pressure difference may cause sufficient water to leak through so as to constitute a nuisance. If the lowered pressure is on the hot water line  20 , no “leak” will occur as the higher pressure of the cold water inside the sleeve  232  will hold it against the inner wall of tubular spool  204  in the vicinity of hot bleed hole  234 , effecting a seal. If the lowered pressure is on the cold side, the valve  200  will allow cooled off water from the hot water line  20  to bypass into the cold water line until warm water arrives at the valve  200 , at which time the shuttle  218  will shift and cut off the bypass. 
       Example 3  
     Dual Handle, Single Spout Faucets 
       [0063]    Although two handle, single spout faucets might have been expected to fade out of demand in favor of the more convenient single handle faucets, the two handle faucets (shown as  10  in  FIG. 1 ) seem more amenable to elegant cosmetic design than their single handle cousins, which have an inherently more utilitarian look. Apparently for this reason, most double handle faucets on display are for lavatory use. The same requirements for ease of maintenance by allowing access to the bypass valve  36  from the top apply to this faucet type. It is convenient that the prior art faucet design utilizing a rotating threaded stem with a faucet washer and a hard seat has become a thing of the past, as the newer designs with replaceable cartridges are more adaptable to this modification. 
         [0064]    Most modern two handle faucets utilize a cartridge design in a pair of valve member  166 , shown in  FIG. 16 , wherein the valving function is accomplished within the cartridge that is positioned inside the housing section  168  of valve member  166 . This allows complete re-conditioning of the faucet by simply replacing a single assembly on each side. These cartridges are accessible in the housing section  168  from the top by removing the faucet handles and bonnets that attach to the upper threaded portion  170 . The cartridge assembly then simply lifts out, exposing its open cavity inside housing section  168 , with a side port  172  leading to confluence with the like port from the other side of the faucet, which confluence flows on through the single spout of such faucets. Below the mentioned cavity for the faucet valving cartridge there is an open one-half inch (typically) threaded pipe  174  for the hot or cold conduit into the faucet. This externally threaded pipe is substantially longer than needed for valving or connection purposes to allow for overly thick lavatory counters and to get the lower end of these threaded pipes far enough down behind the sink for reasonable access by the installer. This “extra” space on the hot water side is a top accessible, hydraulically appropriate place to locate a thermal valve cartridge similar to the type described for inclusion in or adjacent to the hot water conduit in the central housing  62  of a single handle faucet. Side port  175  is added to housing section  168  and a line is run to a like port on the other, opposing faucet. Addition of a thermal bypass valve  36  requires additional machining and the addition of a bypass line connecting the hot and cold lines. An existing two handle single spout valve thus could not be retrofitted, but modifications to the design are relatively minor and the existing replaceable valve cartridge would fit the new design. 
         [0065]    The major difference of concern in this matter between single handle single spout and two handle single spout faucet designs is that in the single handle central block, it is possible to create the connecting passages (bypass) by simply drilling cross holes, as discussed above. With two separate hot and cold faucet valves located four inches apart, some kind of cross conduit for the bypass must be added. There seem to be two approaches to directing the water from the hot and cold faucets to a confluence and out to the single spout. American-Standard, Oasis, La Bella and some Price-Pfisters use a large brass casting that includes the spout, both hot and cold faucet housings, and a cored cast passage connecting all of this together. Adding a thermal bypass valve  36  to such a two handle faucet set would require the addition of an additional cored cast passage to accomplish the bypass function between hot and cold lines. Delta, Moen, Kohler, and some Price Pfister two handle single spout valves use brazed-in copper tube manifolds instead of cored cast passages. These would require the addition of a tubular cross passage brazed in. The Delta two handle single spout valve has a somewhat different valving action which makes it much more difficult to fit in a thermal valve cartridge. This new passage (cored or brazed tubular) needs to connect to the vertical hot and cold “pipe” members below their existing side port to the spout. These faucet sets generally do not have sufficient vertical space under the polished bezel to accommodate the extra passage. This will require addition of some vertical length to the skirt of the valve bezel. 
         [0066]      FIG. 17  shows a modified “hot” side of a Kohler two handle faucet  176 , with the housing shown as  178 . The housing  178  is identical to the standard existing Kohler housing  178  above (to the right of) line AA. The housing  178  must be bored out in several steps to accommodate the new thermal valve cartridge  180 , which can be a molded plastic cartridge identical in function to that already described for the center block of the Delta single handle valve. It varies from the previously described cartridge in the configuration of the passage to bring the hot water past the thermal valve  36  to the faucet, and the configuration of the snap fit for the thermal actuator  88 . It also has an upper extension  182  with a through hole  184 . The extension  182  fits into a recess in the bottom of the existing Kohler faucet cartridge and the through hole  184  is for engagement of a hook to allow removal of the thermal valve cartridge  180  for replacement of the thermal bypass valve  36 . 
         [0067]    The operation of the bypass valve  36  inside of faucet  10  of the present invention is summarized on the chart shown as  FIG. 18  which indicates the results of the twenty combinations of conditions (pump on/pump off; hot water line hot/hot water line cooled off; hot faucet on, or off, or between; cold faucet on or off, or between) that are applicable to the operation of valve  36 . The operating modes IVB, IVC, IVD, IIIB, &amp; IIID are summarized detailed in the immediately following text. The operation of the remaining fifteen modes are relatively more obvious, and may be understood from the abbreviated indications in the outline summarizing  FIG. 18 . Starting with the set “off” hours (normal sleeping time, and daytime when no one is usually at home) pump  26  will not be powered. Everything will be just as if there were no pump  26  and no bypass valve  36  installed in faucet  10  (i.e., both the cold and hot water lines will be at the same city water pressure). The hot water line  20  and bypass valve  36  will have cooled off during the long interim since the last use of hot water. The reduced temperature in the valve results in “retraction” of rod member  40  of the thermally sensitive actuator  88 . The force of bias spring  106  pushing against flange  46  on rod member  40  will push it back away from valve seat  90 , opening valve  36  for recirculation. Although the thermal actuating element  88  is open, with pump  26  not running, no circulation flow results, as the hot  20  and cold  16  water piping systems are at the same pressure. This is the mode indicated as IVB in the outline on  FIG. 18 . If the cold water valve at faucet  10  is opened with the thermal element  88  open as in mode IVB above, pressure in the line  16  to the cold water side of faucet  10  will drop below the pressure in the hot water line  20 . This differential pressure will siphon tepid water away from the hot side to the cold side, which is the mode indicated as IVD in the outline on  FIG. 18 . The recirculation of the “hot” water will end when the tepid water is exhausted from the hot water line  20  and the rising temperature of the incoming “hot” water causes the thermal element  88  to close. 
         [0068]    If the hot water valve is turned on with the thermal element  88  open as in mode IVB above, pressure in the line  20  to the hot water side of faucet  10  will drop below the pressure in the cold water line  16 . This differential pressure, higher on the cold side, will load check valve  96  in the “closed” direction allowing no cross flow. This is mode IVC in the outline on  FIG. 18 . In this mode, with the hot water line  20  cooled and the pump off, a good deal of cooled-off water will have to be run (just as if valve  36  were not installed), to get hot water, at which time the thermal element  88  will close without effect, and without notice by the user. With the thermal element  88  open and the hot water line  20  cooled-off as in mode IVB above, at the preset time of day (or when the cyclic timer trips the next “on” cycle) the pump  26  turns on, pressurizing the water in the hot side of faucet  10 . Pump pressure on the hot side of faucet  10  results in flow through the open thermal element  88 , thereby pressurizing and deflecting the check valve  96  poppet away from its seat to an open position. Cooled-off water at the boosted pressure will thus circulate from the hot line  20  through the thermal element  88  and check valve  96  to the lower pressure cold line  16  and back to water heater  18 . This is the primary “working mode” of the bypass valve  36  and is the mode indicated as IIIb in the outline on  FIG. 18 . If the cold water valve is turned on during the conditions indicated in mode IIIB above (i.e., pump  26  operating, hot line  20  cooled off, the hot valve at faucet  10  off) and while the desired recirculation is occurring, mode IIID will occur. A pressure drop in the cold water line  16  due to cold water flow creates a pressure differential across valve  36  in addition to the differential created by pump  26 . This allows tepid water to more rapidly bypass to the cold water inlet  22  at faucet  10 . When the tepid water is exhausted from the hot water line  20 , thermal element  88  will close, ending recirculation. 
       Explanation of FIG.  18  Table 
       [0069]    MODE 1: Water In Hot Water Supply Line Hot, Pump On.
       A. Hot and cold faucet valves full open
           Pressure drops from hot and cold flow about equal. Actuator element  26  stays closed. No leak or recirculation in either direction.   
           B. Hot and cold faucet valves fully closed
           Thermal actuator  88  keeps valve  36  closed. No recirculation.   
           C. Hot faucet valve fully open, cold faucet valve closed
           Actuator element  88  closed. Check valve  96  closed. No recirculation. No leak.   
           D. Hot faucet valve closed, cold faucet valve fully open
           Actuator element  88  closed. No recirculation. No leak.   
           E. Hot and cold faucet valves both partially open in any combination
           Actuator element  88  closed. No recirculation. No leak.   
               
 
         [0080]    MODE II: Water in Hot Water Supply Line Hot, Pump Off.
       A. Hot and cold faucet valves full on
           Pressure drops from hot and cold flow about equal. Actuator element  88  stays closed.   
           B. Hot and cold faucet valves fully closed
           Thermal actuator  88  keeps valve  36  closed. No recirculation.   
           C. Hot faucet valve fully open, cold faucet valve closed
           Thermal actuator  88  closed. Check valve  96  closed. No recirculation. No leak.   
           D. Hot faucet closed, cold faucet fully open
           Thermal actuator  88  closed. No recirculation. No leak.   
           E. Hot and cold faucets both partially open in any combo
           Thermal actuator  88  closed. No recirculation. No leak.   
               
 
         [0091]    MODE III: Water in Hot Water Line Cooled Off, Pump On.
       A. Hot and cold faucet valves full open
           Flow-induced pressure drops about equal, valve  36  stays open and allows recirculation hot to cold until tepid water is exhausted and hotter water closes thermal actuator  88 . If both faucet valves are at same sink, they are mixing hot and cold anyway. If faucet valves being manipulated are at remote sinks on the same plumbing branch, this short time tepid-to-cold leak will probably not be noticeable. If faucet valves being manipulated are on remote branches of plumbing, the mixing would have no effect.   
           B. Hot and cold faucet valves fully closed
           Thermal actuator  88  open, get desired tepid-to-cold recirculation until hot line heats up.   
           C. Hot faucet valve fully open, cold faucet valve closed
           Thermal actuator  88  open but pressure drop in hot line may negate pump pressure, stopping recirculation. Check valve  96  stops cold to hot leak.   
           D. Hot faucet valve closed, cold faucet valve fully open
           Thermal actuator  88  open, get tepid to cold recirculation until hot line heats up.   
           E. Hot and cold faucets both partially open in any combination
           Could get tepid to cold leak. If faucet valves at same sink don&#39;t care as mixing hot and cold anyway. If at remote sinks probably not noticeable. Tepid to cold leak would be short term.   
               
 
         [0102]    MODE IV: Water In Hot Water Supply Line Cooled Off, Pump Off.
       A. Hot and cold faucet valves full open       
 
         [0104]    Flow-induced pressure drops about equal, valve  36  stays open and may allow recirculation (leak) hot to cold until tepid water is exhausted and hotter water a long shallow groove  190  in or a reduced diameter of piston  44  that would extend from just inside the guide bore  186  (at full extension) to just outside the guide bore  186  at full retraction would provide a recess to contain buildup for a long period. Once this recessed area filled up with lime, the edge  188  of guide bore  186  could scrape off the incrementally radially extending soft build up relatively easily, as compared to scraping off the surface layer that bonds more tenaciously to the metal. 
         [0105]    The most direct method to overcome sticking due to mineral buildup is to optimize actuator force in both directions. Buildup of precipitated minerals on the exposed outside diameter of the extended piston  44  tends to prevent retraction, requiring a strong bias spring  106 . This high bias spring force subtracts from the available extending force however, thereby limiting the force available to both extend the piston  44  against the mineral sticking resistance and to effect an axial seal between poppet and seat. 
         [0106]    When water temperature is high, the piston  44  is extended so that its surface is exposed. Deposition also occurs primarily at high temperatures, so that buildup occurs on the piston outside diameter, resulting in sticking in the extended position when the growth on the piston outside diameter exceeds the guide  186  interior diameter. Significantly more than half of the available actuator force thus can most effectively be used to compress the bias spring  106 , resulting in a maximum return force. 
         [0107]    While there is shown and described herein certain specific alternative forms of the invention, it will be readily apparent to those skilled in the art that the invention is not so limited, but is susceptible to various modifications and rearrangements in design and materials without departing from the spirit and scope of the invention. In particular, it should be noted that the present invention is subject to modification with regard to the dimensional relationships set forth herein and modifications in assembly, materials, size, shape, and use. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope. 
         [0108]    It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.