Patent Publication Number: US-2010126604-A1

Title: System and Method for On Demand Hot Water Distribution

Description:
RELATED APPLICATIONS 
     The present application claims priority from U.S. Provisional Application Ser. No. 61/115,931 filed Nov. 18, 2008, which is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     1. Field 
     The embodiments of the invention relates generally to systems and methods for hot water distribution and more particularly to systems and methods for on demand hot water distribution to one or more specified fixtures. 
     2. Background 
     In conventional residential hot water systems, a cold water supply line is provided to the inlet of the water heater and a hot water distribution line exits from the outlet of the water heater. The hot and cold water distribution lines are then plumbed throughout building to the various fixtures located throughout the house. 
     While conventional systems operate well to distribute water, conventional systems are not energy efficient and such systems result in a tremendous waste of water. In a conventional system, after each use the water in the hot water distribution line cools off, consequently, when a faucet is turned on, the water is usually cooler than desired and the user allows the water to run until the cooled off hot water is purged from the line and hot water arrives at the fixture. Waiting for the hot water to arrive is irritating to the user, and it increases water consumption resulting in an increase in the user&#39;s water bill. 
     A number of systems have been developed in an attempt to solve this problem. For example, there are systems that circulate hot water continuously through the hot water distribution piping, and back to the water heater through a dedicated return line. These types of systems provide nearly instant hot water and eliminate water waste, but such systems waste significant energy. These systems result in hot water being circulated throughout the distribution system even if there is no demand for hot water. Keeping the piping full of water that is higher in temperature than the ambient temperature causes a large loss of heat energy, in order to keep the temperature up, more energy is used which increases the user&#39;s energy bill and greenhouse gas emissions. 
     In an attempt to curtail the energy use described in the constant circulating hot water systems, many users put such systems on a timer so that the system runs only during hours of normal use. This creates an inconvenience when hot water is desired during off hours, and still is very costly and wastes energy. Another problem with this type of system is that if the home was not plumbed with a hot water return line, it can be very expensive to add plumbing to an existing home. Moreover, this type of system will not work with a tankless water heater. 
     In an alternative to a designated hot water return line, some conventional circulating systems use the cold water distribution line as the hot water return line. One such system is described in U.S. Pat. No. 5,829,467. The system discloses a pump located at the water heater and special temperature sensing cross over valves at the fixtures. The pump runs continuously, but can only make water flow if one or more of the cross-over valves at the fixtures is open. The valves are open if the water passing through them is cold, and when the water reaches a preset temperature the valve closes. This keeps warm water near the fixtures and thus reduces the wait for hot water. 
     However, disadvantageously, this type of system results in the hot water distribution piping being full of above ambient temperature water all the time and much if not all of the cold water distribution lines are also above ambient temperatures. Consequently, there is a huge amount of energy wasted, greenhouse gas emissions are increased and it is very costly to operate. This type of system also does not work with tankless water heaters. 
     The reason these systems will not work with tankless water heaters is because tankless water heaters are turned on when water flows through them and activates a flow switch. These types of circulating systems do not produce enough flow to turn on a tankless water heater. Excess water flow voids the warranty on tankless systems. 
     Furthermore, many homeowners don&#39;t like the above described systems because lukewarm water as opposed to cold water is distributed when a cold fixture is opened. These systems require the line to be purged in order to get cold water, resulting in a waste of energy and water. 
     Another type of system, for example the Laing System, uses a small pump and valve at a fixture. The pump runs periodically to keep the water at the fixture above ambient temperature. When the water at the fixture cools to a preset temperature the pump turns on and when the water reaches another preset elevated temperature the pump turns off. Like the above described systems this system results in the hot water piping and much of the cold water piping to be at above ambient temperatures and thus wastes energy. In addition, this system only serves the site where the pump and valve are located and any fixtures directly between the pump/fixture and the water heater. As with the previous system cold water is harder to obtain, and the Laing systems do not work with tankless water heaters. 
     Yet another type of system that uses the cold water line as a hot water return line is a demand type system. With this type of system the user needs to “demand” hot water by pressing a button or otherwise activating the pump. The pump (and valve) is located at the fixture where the user desires fast hot water. When the user wants hot water he activates the pump, which begins pumping hot water from the water heater to the fixture. When a sensor in the pump detects an increase in temperature it shuts the pump off so that no warm water enters the cold water line. When the user turns on the faucet he only has to wait for a few seconds for hot water (not warm). This system results in less water running down the drain unused while waiting for hot water than other types of non-demand systems. By using a powerful pump, the water can be delivered very rapidly. 
     Another advantage of demand type systems is that they can be used with tankless water heaters. In fact, because it takes longer to get hot water with a tankless water heater than with a storage type water heater, demand systems are particularly useful for tankless installations. 
     However, with most installations a demand system provides hot water to only one or two fixtures. To cover all of the fixtures requires multiple pumps. Even in instances where one pump can provide water to more than one fixture, it is not ideal situation because it results in filling more of the distribution piping with hot water than is needed to provide the hot water to a particular fixture. 
     An optimally efficient system only fills the piping between the water heater and the fixture being used with hot water, none of the systems currently available have this advantage. Embodiments of the present invention provide novel systems and methods of efficiently delivering hot water to any fixture in a home without running water down the drain, and without wasting energy. Furthermore embodiments of the present invention eliminate the need for multiple pumps, and provide novel systems that can be easily and inexpensively retro-fitted to existing homes, even homes with tankless water heaters. 
     SUMMARY 
     Embodiments of the present invention disclose systems and methods for distributing hot water on demand or on a specified schedule. 
     Further embodiments disclose a method of distributing hot water using a distribution system which includes a water heater, a pump with an electronic pump controller, one or more crossover valves with controllers, a cold water conduit, a hot water conduit, one or more hot and cold water outlets, with the cold water conduit being coupled to the water heater inlet, a source of cold water, any cold water outlets at the fixtures, and the outlets of any crossover valves, the hot water conduit being coupled to the water heater outlet, any hot water outlets at the fixtures, the inlets of any crossover valves, and comprising the steps of: the user activates a valve controller at a particular fixture the valve controller checks the water temperature at the valve, and if the water temperature is above a specified value, the valve controller does nothing if the temperature is not above the value, the valve controller at that fixture opens the valve and sends a start signal to the pump controller the pump controller turns on the pump the pump controller optionally looks for a turn off signal when the valve controller detects an increase in temperature and sends a turn off signal to the pump controller, shutting the pump off. If the pump controller does not receive a turn off signal within a specified time period the pump shuts off anyway. 
     Still other embodiments provide a method of distributing hot water wherein the user activates a valve controller at a particular fixture The valve controller checks the water temperature at the valve, and if the water temperature is above a specified value, the valve controller and optionally emits a sound or signal to indicate to the user that hot water is available. If the water temperature is not above a designated temperature, i.e., the water is not hot, the valve controller at that fixture opens the valve, sends a start signal to the pump controller, and emits a sound to indicate hot water is on the way. The pump controller then turns on the pump and the pump operates to dispense hot water through the distribution system until an increase in temperature is detected. When the valve controller detects an increase in temperature it shuts off the valve, and optionally sends a stop signal to the pump controller, and emits a sound or signal to indicate to the user that the hot water has arrived. The pump controller shuts off the pump. 
     In an alternative embodiment, if the pump controller does not receive a shut off signal within a specified time period, such that hot water continues to flow through the distribution system, the pump automatically shuts off when the specified period of time has elapsed. However, if the none of the valves are open, the valve will automatically shut down as there is be no water flowing in the system. 
     In yet another embodiment, a system for distributing hot water includes a water heater, a pump with an electronic pump controller, one or more crossover valves with controllers, a cold water conduit, a hot water conduit, one or more hot and cold water outlets where the cold water conduit is coupled to the water heater inlet, a cold water source, at least one cold water outlet at the fixtures, and the outlets of any crossover valves, the hot water conduit being coupled to the water heater outlet, at least one hot water outlet at the fixtures, and the inlets of any crossover valves. I 
     Embodiments of the present invention also provide a method for distributing hot water including a user activating a valve controller at a particular fixture, the valve controller or automatic device sending a pump controller a function code, the controller receiving the code and implementing a software program identified by the function code, Upon completion of the program the pump controller returning to the default program and awaits further instructions. 
     In an alternative embodiment, an automatic device or sensor activates a valve controller at a specified fixture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an embodiment of a system for hot water distribution; 
         FIG. 2  depicts an embodiment of a basic system for hot water distribution; and 
         FIG. 3  depicts an embodiment of a basic system for hot water distribution when implemented with a dedicated return line. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     Various embodiments of the invention are described hereinafter with reference to the figures. It should also be noted that the figures are only intended to facilitate the description of specific embodiments of the invention. The embodiments are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an aspect described in conjunction with a particular embodiment of the invention is not necessarily limited to that embodiment and can be practiced in any other embodiment of the invention. 
     Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrase “in one embodiment” as used herein does not necessarily refer to the same embodiment, though it may. Furthermore, the phrase “in another embodiment” as used herein does not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention. 
     In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.” The term “coupled” implies that the elements may be directly connected together or may be coupled through one or more intervening elements. 
     The present invention discloses embodiments of systems and methods for distributing hot water to a specified fixture. As will be appreciated by one of skill in the art, the systems and methods disclosed are equally applicable to residential, commercial and industrial applications. The purpose of the embodiments is to minimize the waste of water or energy in distributing hot water. 
     As depicted in  FIG. 1 , embodiments of systems of the present invention include a pump  3 , a pump controller  4 , a source of cold water  1 , a water heater  2  with an inlet and outlet  2 B,  2 A, one or more fixtures  8 ,  12 ,  16  with hot and cold water outlets a cross over valve  5 ,  11 ,  15  and controller  6 ,  13 ,  17 , at each fixture  8 ,  12 ,  16 , a conduit in fluid communication with the source of cold water  9 , the cold water outlets at the fixtures, the outlets of the cross over valves  9 A,  9 B,  9 C, and the water heater inlet  2 B, a conduit in fluid communication with the outlet  2 A of the water heater  10 , the hot water outlets at the fixtures  8 ,  12 ,  16  and the inlets of the cross over valves  9 D,  9 E,  9 F. Embodiments of the present invention further include a pump activation means comprising at least one of a number of possible devices such as but not limited to buttons, motion detectors, clock timers, and other mechanical and electronic sensors. 
     When hot water is desired at a specified fixture, a pump activation means communicates with pump controller conveying to the controller at the outlet of the hot water heater that hot water is desired. The valve controller checks the water temperature at the cross over valve to make sure hot water is not already supplied to the specified fixture. If hot water is not present at the specified fixture, the valve controller sends the pump controller a start signal and a function code that selects the software program to be implemented by the pump controller. 
     The pump controller obtains a function code. The function code is sent to the pump controller as a result of an initiating action at a select fixture. The function code operates to select the software program to be run by the pump controller. For example, the function code may direct the pump controller to run a program such that hot water is sent to a single fixture, it could direct the pump controller to run a program for freeze protection, or any other pre-established program for operating the hot water distribution system. 
     If for example the device is a simple button to obtain hot water from a fixture, the valve controller will first check the temperature of the water at that location. If the temperature is already high, the controller will beep twice which tells the user the water is already hot. If the temperature is not too hot, the controller beeps the activation device once telling the user that the hot water is on the way, and sends a signal to the pump controller requesting service and providing a function code. The valve turns on if the water is not already hot when the button was pressed. 
     The pump controller reads the function code and uses that to determine which program to run. If it is the function to obtain hot water, the pump turns on and pumps until it receives a stop signal or if no stop signal is received in a specified amount of time it shuts off. If it is a function to enter one of the other modes of operation then it does so. 
     When a sensor in the valve senses an increase in temperature the valve controller shuts the valve, communicates with the pump controller telling it to shut off, then beeps to let the user know that hot water has arrived at the fixture. 
     If the activating device is an outdoor freeze protection temperature monitor, the pump controller would open all of the valves; turn on the pump, and then when the last valve has closed shuts the pump off, with the cycle repeating at regular intervals until the danger is over. 
     A clock/timer device could be used to activate the system. The pump controller and valve controllers would receive a function code telling them to duplicate a temperature controlled type circulating system at one or more specified locations that could be programmed into the clock/timer device. This mode could last for a period programmed into the clock/timer device. 
     The activation devices can be manually operated buttons, motion detectors, proximity detectors, timers, clocks etc. 
     Turning now to the figure.  FIG. 1  depicts a piping diagram of a system for distributing hot water. The distribution system includes: a pump, a pump controller, a source of cold water, a water heater with an inlet and outlet, one or more fixtures with hot and cold water outlets, a cross over valve and controller at each fixture, a conduit in fluid communication with the source of cold water, the cold water outlets at the fixtures, the outlets of the cross over valves, and the water heater inlet, a conduit in fluid communication with the outlet of the water heater, the hot water outlets at the fixtures and the inlets of the cross over valves. Embodiments of the present invention further include a pump activation means comprising at least one of a number of possible devices such as but not limited to buttons, motion detectors, clock timers, and other mechanical and electronic sensors. 
     When hot water is desired at a sink  8 , a user presses a button  7 . The user initiates the delivery process by pushing a button or activating a sensor in some way. The button, motion sensor, light beam, or whatever method is being employed to activate the demand system as described below to turn the pump on and open the valve associated with the fixture in question. The button  7  is wired to a controller  6  for a valve  5  at the sink  8 . When the button  7  is depressed a program is initiated in the valve controller at the sink  8 . The controller  6  begins by sampling the water temperature using a temperature sensor that is integral with the valve and the controller  5 . Although described as integral with the valve and controller, it is contemplated within the scope of the embodiments of the present invention that the temperature sensor could be a separate device, could be integral with the fixture, ideally located at the junction of the fixture and the hot water inlet to the fixture, or positioned in any such way that the temperature could be measured before dispensing the water through the fixture. If the temperature is below a critical value (i.e., a specified pre-designated temperature), the controller  6  opens the valve  5 , and turns on a pump  3 . An audible or visual signal is emitted to advise that a request for hot water has been made. The temperature sensor monitors the temperature at the valve  5 . When the temperature sensor detects an increase in temperature of the water, preferably in the range of 6 to 12 degrees, this range is not intended to be a limitation on the embodiments of present the invention, it sends a signal to the controller  6  to shut the valve  5  and pump  3  off. An alternate sound or signal is emitted to indicate to the user that the hot water has arrived. 
     If when the button  7  is pushed, the temperature sensor  6  senses an already elevated temperature, then it may not open the valve  5  or start the pump  3 , but just emitted an alternate sound or signal to indicate that the water is already hot. Alternatively, if an elevated temperature is measured but the temperature is not within the specified temperature range, the valve  5  may be opened and the pump  3  run for a shorter period of time to result in hot water at the desired temperature at the fixture. 
     The valve controller  6  may automatically, without user intervention, send a shut-down signal to the pump controller  4  after a specified time period elapses, i.e. three minutes, so that hot water ceases to be pumped through the distribution system. 
     In another alternative embodiment, a motion detector could activate the demand feature as a user enters a bathroom or the kitchen, in this embodiment, similarly an audible or visual signal is emitted to signal hot water is on the way. 
       FIG. 1  also depicts the hot water distribution system operating as a freeze protection system for the potable water system. When operating as a freeze protection system the systems is initiated when the temperature outside of the house drops to freezing or below. When the external temperature drops, the external temperature activation device  19  sends a function code to the pump  3  which then sends commands to specified valves located throughout the distribution system  5 ,  11 ,  15  directing the various valves to open and emitting a sound or signal to alert potential users that the freeze protection mode has been activated. When the outside temperature rises above freezing or the system is not in danger of freezing, the activation device  19  communicates to pump controller  4  and the freeze protection system is deactivated. The system then returns to its demand mode of operation. 
     In an alternate embodiment, a signal from a clock timer activation device  20  instructs the pump controller  4  and designated valve controllers  5 ,  11 ,  15  to enter a temperature controlled circulating system mode. After a pre-programmed period of time, the clock timer  20  sends a signal to the pump controller  4  to return to demand system mode. When operating in this mode, the system operates like a conventional demand system, but affording the ability for hot water to be available at all fixtures in the system. The clock timer activation device  20  can be user programmed to provide hot water to one or more specified fixtures or even all fixtures at once. The clock timer device  20  also provides for user programming for any specified period of time that the system remains in a timer/temperature mode. 
     In the systems described, the pump and valve controllers are micro-controller based. The pump and valve controllers are controlled with software programming with minimal interface programs as is known to one of skill in the art. The pump may be any suitable pump with the capability to be electrically controlled. The more powerful the pump employed, the more quickly the hot water will arrive at the selected fixture. Similarly, any suitable electrically controlled valve or combination of valves may be used in the above described embodiments. 
     In various embodiments the pump controller, valves, and activation devices communicate with each other via hardwiring, through power line signals, or via radio frequency links. The valves and activation devices obtain power through the house wiring alternatively, if the system is a retrofit battery power or alternate power may be utilized. The utilization of battery power makes the system very easy to install even in retrofit applications. 
     The pump controller, valve controllers, and activation devices may employ microcontrollers and associated circuitry to provide the various functions. 
     By using a large powerful pump and high flow valves the system may also be implemented in apartment buildings with central water heaters and other commercial and industrial applications. 
     In another embodiment, the on demand system is initiated without user interaction when a dishwasher is turned on, and the motor operates to open the drain valve, the drain valve is wired to a controller for a valve at the water inlet line. When the valve opens a program is initiated in the valve controller at the water inlet line. The controller begins by sampling the water temperature using a temperature sensor that is integral with the valve and the controller. Although described as integral with the valve and controller, it is contemplated within the scope of the embodiments of the present invention that the temperature sensor could be a separate device, could be integral with the dishwasher, ideally located at the water inlet of the dishwasher or positioned in any such way that the temperature could be measured before dispensing the water into the dishwasher. If the temperature is below a critical value (i.e., a specified pre-designated temperature), the controller opens the valve, and turns on a pump. In this embodiment, it is not essential that an audible or visual signal is emitted to advise that a request for hot water has been made as the user is not waiting for hot water. The temperature sensor monitors the temperature at the valve. When the temperature sensor detects an increase in temperature of the water, preferably in the range of 6 to 12 degrees, this range is not intended to be a limitation on the embodiments of the present the invention, it sends a signal to the controller to shut the valve and pump off. Optionally an alternate sound or signal is emitted to indicate to the user that the hot water has arrived. 
     In yet another embodiment, a user may initiate a signal for hot water to be delivered to the water inlet of the dishwasher by depressing button in communication with the water inlet line to the dishwasher in a manner similar as that described in conjunction with hot water delivery at a faucet. 
     In still another embodiment, the dishwasher may initiate a signal for hot water when the motor commences operation regardless of whether or not the drain valve opens. 
     In another embodiment, the high efficiency hot water delivery system is simplified such that the pump controller need not know which valve is turned it on. This embodiment comprises of a pump with controller at the water heater and a valve with controller under the sink. The pump is coupled to the water heater between the cold water supply and the water heater inlet, with the cold water distribution plumbing connection on the inlet side of the pump. 
     A valve with integral temperature sensing means is coupled between the hot and cold supply lines at the fixture, and the valve controller has terminals for a start button. 
     Pressing or otherwise engaging the start button causes the valve controller to check the water temperature. If the water is not already hot, the valve controller opens the valve and sends a start command to the pump controller which starts the pump. When hot water reaches the valve it closes, preventing heated water from entering the cold water piping. 
     When the pump controller receives the start command from the valve controller it turns on the pump for a pre-determined and adjustable amount of time. The predetermined amount of time is preferably 3 minutes. However, it may be a longer or shorter period of time, preferably is it between 1 minute and 5 minutes. 
     Because the valve closes when the hot water reaches it, the pump can keep running with no adverse effects, because with the valve closed no flow will occur. 
     Pressing or otherwise engaging the button on any valve starts the pump and sends the hot water to the fixture for with the button was engaged and only that fixture. If multiple valves are activated at the same time then hot water will flow to each of the fixtures and only those fixtures where valves were activated. 
     The system also includes scald protection as there is the chance that a user might activate a valve while another user is taking a shower in another location. Such activity could result in the pump causing a difference in pressure between the hot and cold distribution conduits resulting in the possibility of a scalding accident. 
     To prevent scalding, the pump controller may be connected to a flow switch inserted into the cold water conduit or otherwise placed to control flow. If water is flowing into the house plumbing, the controller will not allow the pump to turn on. If the pump is already running it shuts off. This eliminates the possibility of scalding. 
     In another embodiment, the system may be operated using a wireless or other remote system for activations. In such an embodiment the valve controller is mounted under the sink and has terminals to connect a start button. Alternatively it could also have a built in RF receiver allowing it to be activated wirelessly. the latter configuration allows for convenient night-stand placement of switches etc. 
     In another embodiment, the hot water flow may be activated without specific user intervention, i.e., proactively making a request by depressing a button or taking other overt action. In this configuration, the valve controller utilizes pressure or flow sensing means for activation. For example; briefly turning on the hot water faucet could be used for activation eliminating unsightly buttons. 
     In another embodiment, the hot water is activated by appliance use. Utilizing flow switches or current sensors, appliances such as dishwashers and washing machines could activate the valve controllers. 
     In still another embodiment, freeze protection is provided. An outdoor temperature sensor sends the valves a turn-on signal when the outside temperature drops below freezing. It then periodically activates the valve/controllers until the outdoor temperature reaches a safe level. The periodic circulation keeps the piping warm and protected from freezing. In the case of tankless water heaters this would also protect the heat exchanger from freezing as well. 
     The various hot water distribution systems may also comprise timer control. The valve/controllers can respond to start commands from automatic timers or clocks via the start button terminals or via other communication methods. 
     The systems may also comprise a dedicated return line. When the system is used to replace a dedicated return line system a flow switch is located at the water heater inlet or outlet to sense hot water usage. When the flow switch detects hot water usage it turns on the pump for a fixed time period. The fixed period of time may be randomly set, alternatively it may be established or calculated based on the size of the system or the length of pipe runs. For example, it may be set to 2 minutes for a system with 100 feet of pipe, or 4 minutes with a house with 200 feet of pipe. These examples are however non-limiting and the time period could be adjusted as necessary to ensure proper delivery of the hot water. In addition, the fixed period of time may be preset and may vary depending on the time of day and day of the week. In addition the controller can differentiate between a very short usage of hot water and a longer run, turning on the pump only if the hot water is used very briefly. For example, if the hot water is turned on for 1 second or less the pump would start, but over one second the pump would do nothing. 
     In another embodiment the pump shuts off when it senses the arrival of hot water at the pump, and if hot water never arrives, the pump shut offs after a pre-set time period, for example but not limited to 3 to 5 minutes 
     Other and further embodiments of systems of the present invention include a pump, a pump controller, a source of cold water, a water heater with an inlet and outlet, one or more fixtures with hot and cold water outlets a cross over valve and controller at each fixture, a conduit in fluid communication with the source of cold water, the cold water outlets at the fixtures, the outlets of the cross over valves, and the water heater inlet, a conduit in fluid communication with the outlet of the water heater the hot water outlets at the fixtures and the inlets of the cross over valves. 
     Optionally embodiments of the system may include flow sensing/detection means, including but not limited to paddle type flow switches, and turbine type flow sensors, connected between the cold water source and the pump inlet and in communication with the pump controller, flow sensing means connected between the water heater outlet and the hot water distribution conduit and in communication with the pump controller, and flow sensing means connected between the hot water distribution conduit and the hot water faucet and in communication with the valve controller. 
     Embodiments of the present invention may further include valve controller activation means including but not limited to motion detectors, current sensors, photo electric beams, manual switches, and proximity switches, comprising at least one of a number of possible devices such as but not limited to buttons, motion detectors, clock timers, flow sensors, current sensors and other mechanical and electronic sensors. 
     When hot water is desired at a specified fixture, the valve controller at that location is activated causing the valve controller to check the water temperature, and if the water temperature is below a set point, the controller opens the valve and sends a start command to the pump which runs until the fixed run time has elapsed. When the valve controller senses an increase in temperature it closes the valve. 
     In another embodiment,  FIG. 2  depicts an embodiment of a basic system for hot water distribution  200 . The system  200  includes a flow control means, i.e., a first flow switch  210 , to detect the consumption of water. The flow switch  210  prevents a pump  220  from starting or if the pump  220  is already running a pump controller  230  shuts it off, preventing the possibility of a scalding injury. 
     As also shown in  FIG. 2 , a flow sensing means, i.e., a second flow switch  240  ( a . . . n ), is located between a hot water distribution conduit  250  and a hot water fixture  260  ( a . . . n ). There may be multiple flow sensing means in a single system such that a second flow switch  240  ( a . . . n ) is located at each hot water fixture. When the flow sensing means senses flow it activates a valve controller  270  ( a . . . n ) initiating the circulation of hot water. 
     Another embodiment of the system includes flow sensing means or current sensing means, such as series resistor sensing circuits, transformer type current sensing circuits, and clamp on current detectors in communication with the valve controller for activation when an external appliance such as a washing machine or a dishwasher begins operation. 
     Yet another embodiment of the system includes temperature sensing means, including but not limited to thermisters, thermocouples, bi-metallic contact sensors, and integrated circuit sensors located outdoors and in communication with the valve controllers to activate the valve controllers when the outdoor temperature drops below freezing. 
     In another embodiment,  FIG. 3  depicts a basic system  300  for hot water distribution when implemented with a dedicated return line  310 . The dedicated return line employs a flow sensing means  320 , i.e., a flow sensor, between a water heater outlet  330  and a hot water distribution conduit  340  to activate a pump controller  350 , which manages a pump  360 . 
     As depicted, the dedicated return line  310  is used to circulate unused water back to a water heater inlet  370 . This system employs a temperature sensing means  380  in communication with the pump controller  350  and shuts off the pump  360  when a temperature increase is detected. If no increase is detected the pump  360  shuts off after a pre-set fixed time period, for example but not limited to 3 to 5 minutes. 
     In the systems described above, the pump and valve controllers are micro-controller based. The pump and valve controllers are controlled with software programming with minimal interface programs as known to one of skill in the art. The pump may be any suitable pump with the capability to be electrically controlled. The more powerful the pump employed, the more quickly the hot water will arrive at the selected fixture. Similarly, any suitable electrically controlled valve or combination of valves may be implemented in the above described embodiments. 
     In various embodiments the pump controller, valves, and activation devices communicate with each other via hardwiring, through power line signals, or via radio frequency links or any other system that enable communication. The valves and activation devices may obtain power through the house wiring. Alternatively, if the system is a retrofit, battery power or alternate power may be utilized. The utilization of battery power makes the system very easy to install even in retrofit applications. 
     Although the systems described above include a pump, any pumping means, including but not limited to centrifugal pumps, gear pumps, diaphragm pumps, piston pumps, and turbine pumps, are contemplated within the scope of the embodiments of the present invention. 
     Although described in conjunction with a single use or single unit application, such description is not so limited and further expansions and implementations are contemplated within the scope of the embodiments of the present invention. The system is equally applicable for large scale or multi-unit use. By using a large powerful pump and high flow valves the system may be implemented in apartment buildings with central water heaters and other commercial and industrial applications. 
     As noted previously the forgoing descriptions of the specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments of the invention to the precise forms disclosed and obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to explain the principles of the embodiments of the invention and its practical applications, to thereby enable those skilled in the art to best utilize the invention and various embodiments thereof as suited to the particular use contemplated. It is intended that the scope of the invention and embodiments thereof be defined by the claims and their equivalents.