Abstract:
A plumbing system which, when ambient outdoor temperatures drop below freezing, circulates water to prevent it from freezing, utilizing a check valve to prevent water from flowing back into the water main and further utilizing a relief valve which can open to the atmosphere and relieve pressure in the system if necessary. The system can have two separate circulation pumps, one for hot water and one for cold water.

Description:
RELATED APPLICATION DATA 
     This application is a continuation-in-part of U.S. patent application, Ser. No. 09/049,832, filed on Mar. 27, 1998, now U.S. Pat. No. 5,950,653, the content of this reference is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to freeze-resistant plumbing systems in structures located in areas where the ambient temperature declines to a point below freezing, causing water within existing plumbing systems to freeze and damage or destroy the plumbing systems. 
     BACKGROUND OF THE INVENTION 
     In cold climates, water in plumbing systems tends to freeze and expand when exposed to temperatures below freezing. When structures are vacant or when water pipes are either exposed or located in attics or exterior walls, the expansion of frozen water may cause the pipes to rupture, leading to water damage when the pipes thaw and water flow resumes. 
     Keeping water moving throughout the system is effective in preventing water from freezing in the pipes during a cold spell. Hence, people open faucets to drip, maintaining water movement. However, this practice wastes water and may cause water pressure problems. 
     Prior art methods use circulating water to prevent frozen pipes. U.S. Pat. No. 4,672,990 describes a system with restrictive connections between the hot water and cold water supply lines. However, migration of water between the lines would result in “warm” cold water and “cool” hot water. Further, the increased pressure caused by the circulating pump could pump water back into the main water supply, contaminating it. 
     U.S. Pat. No. 5,318,059 describes a method of warming cold water by mixing it with hot water and conducting it to the cold water main line. Again, the homeowner would get “warm” cold water or “cool” hot water. 
     SUMMARY OF THE INVENTION 
     The present invention is a true water circulatory system, with no expensive branch lines, by-pass lines, shunt lines, or cross-connects. The cold water circulation system is separate from the hot water circulating system, with a separate circulating pump for each system. The system requires no large mixing tanks or space-consuming expansion tanks. When the ambient outdoor temperature drops below a predetermined temperature (e.g. 34° Fahrenheit) a temperature-sensitive switch will energize the circulation pumps, forcing the water to flow continuously through the system. The system operates in conjunction with a backflow preventer with a pressure relief valve; when the circulation pumps are running, the operation of the backflow preventer will prevent water from being pumped back into the main water supply. No pressure relief valve is required for the water heater in this system. Ordinary plumbing materials such as copper and CPVC (chlorinated polyvinyl chloride) pipe are used in building this system. Valves are fixed to the pipes by pipe threads, bolts, flanges, adhesives, welding, or other available means. 
     It is an object of this invention to provide a freeze-resistant plumbing system for residential and commercial applications. 
     Yet another object of the invention is to provide a freeze-resistant plumbing system which does not require mixing cold water with hot water in order to prevent freezing. 
     A further object of the invention is to provide a freeze-resistant plumbing system which is inexpensive to install and operate and which requires little space. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of the system of the preferred embodiment. 
     FIG. 2A is a partial view of FIG. 1, showing a section elevational view of the backflow preventer with a high pressure relief valve. 
     FIG. 2B is a partial view of FIG. 1, showing a section elevational view of the cold water circulation pump. 
     FIG. 3A is a combination section elevational view and schematic diagram of the system of the preferred embodiment during normal operation. 
     FIG. 3B is a combination section elevational view and schematic diagram of the system of the preferred embodiment in an over-pressure mode. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, there is shown a schematic diagram of the plumbing system  1  of the preferred embodiment. The broken rectangle defines a building or structure  2  which utilizes this plumbing system  1 . The thick black lines (with directional arrows) defines a cold water pipe system loop  3  in which cold water will circulate when the plumbing system  1  is activated. The thick dashed lines (with directional arrows) define a hot water pipe system loop  4  in which hot water will circulate when the plumbing system is activated. 
     Water (not seen in this view) flows under pressure from the water main pipe  10  into the intake pipe  11 , through the water meter  12 , through a line pipe  13 , through the first isolation valve  14   1 , through the first check valve  15 , through the second check valve  16  and past the high pressure relief valve  17 , which is normally in a closed position. The water continues flowing through the second isolation valve  18  and through the cold water circulation pump  19 . Normally, pressure from the water main  10  maintains the flow of water; the cold water circulation pump  19  is not actuated and water flows without resistance. The water flows from the cold water circulation pump  19  through the third isolation valve  20  and into the cold water service pipe  21 , from which it will flow either through takeoff valve  59  into water heater inlet pipe  22  or to first cold water valve outlet  23 , or second cold water valve outlet  24 , or third cold water valve outlet  25 , as people open cold water taps at a sink or shower, or flush a commode. The number of various cold water outlets is by design choice and could number over ten. When the cold water circulation pump  19  is actuated, water flows through fourth isolation valve  38  back to the cold water circulation pump  19 .  1   
     Isolation valves  14 ,  18 ,  20 ,  29 ,  30  and  38  allow the interruption of the flow of water within the system of pipes for maintenance purposes.  
     The water heater inlet pipe  22  is connected to takeoff valve  59  from the cold water service pipe  21  and could be a tee joint or a Yjoint, by design choice. The water heater inlet pipe  22  conducts cold water into the water heater  26  wherein the water is heated and channeled into the hot water service pipe  27 . In order to circulate the hot water, a hot water circulation pump  28  is fixed to the hot water service pipe  27  between fifth isolation valve  29  and sixth isolation valve  30 . The hot water return pipe  31  returns water to the water heater  26  for reheating. (Hot water circulation pumps are already used in some structures to make hot water immediately available to users.) 
     The hot water service pipe  27  carries heated water to first hot water valve outlet  32  (possibly a kitchen sink tap), second hot water valve outlet  33  (possibly a bathtub fixture) and third hot water valve outlet  34  (possibly a washing machine line). There could be ten or more hot water valve outlets by design choice. 
     A water heater pressure relief valve  35  is shown suitably fixed to the water heater  26 . The water heater pressure relief valve  35  will allow the pressure in the water heater to escape should the pressure in the water heater  26  rise to a dangerous level. However, if the water heater pressure relief valve  35  fails and the plumbing system  1  becomes over-pressured, the high pressure relief valve  17  would open to atmosphere and would relieve the potentially dangerous high pressure situation. 
     A temperature switch  36  is shown suitably fixed to the outside wall of structure  2 . As the ambient outdoor temperature declines to a predetermined point (i.e. 34° F.), the temperature switch  36  will close and send a signal to actuate the cold water circulation pump  19  and the hot water circulation pump  28 , each of which will pump water through its respective loop. As the water flows through the cold water pipe system loop  3  and the hot water pipe system loop  4 , the water will be prevented from freezing, meaning no damage will result to pipes from ice formation within the pipes. The pressure of the water circulating throughout the plumbing system  1  may exceed the water pressure from the water main pipe  10 ; in that event, it will cause the first check valve  15  and the second check valve  16  to close, keeping any contaminated water or water that has passed through the water meter  12  from flowing back into the main water supply system. 
     A pressure switch  37  is shown suitably fixed to the cold water service pipe  21 . The pressure switch  37  will turn off the energy to either the cold water circulation pump  19  and/or the hot water circulation pump  28  if the pressure within the cold water pipe system loop  3  or the hot water pipe system  4  becomes too high as a result of the water heater&#39;s  26  over heating water and the pressure relief valve&#39;s  35  failing, causing an unsafe increase of pressure within the plumbing system  1 . 
     Referring to FIG. 2A, there is shown a section elevational view of normal flow through the pressure relief system  60 , which operates to prevent contaminated water under pressure from flowing back into the main water supply system. The water  61  (shown as arrows) flows from the direction of the main water supply system. The water pressure from the water main supply system is greater than the thrust exerted by the first biased spring  40  on the first valve disk  41  in the first check valve  15  and the thrust exerted by the second biased spring  42  on the second valve disk  43  in the second check valve  16 . As long as water is being released from one of the cold water valve outlets or one of the hot water valve outlets, water will flow past the first valve disk  41  and second valve disk  43 ; when the hot water valve outlets are closed and the cold water valve outlets are closed, the first valve disk  41  in the first check valve  15  and the second valve disk  43  in the second check valve  16  will close because pressure within the cold water pipe system loop  3  and the hot water pipe system loop (not shown) will equalize the pressure from the main water supply system; the added thrust from the first biased spring  40  on the first valve disk  41  in the first check valve  15  will cause the first check valve  15  to close or will force the first valve disk  41  to compress on the first valve seat  44 , forming a fluid-tight seal; likewise, the added thrust from the second biased spring  42  on the second valve disk  43  in the second check valve  16  will cause the second check valve  16  to close or will force the second valve disk  43  to compress on the second valve seat  45 . 
     Under normal operating conditions, the high pressure relief valve  17  will remain closed; the water pressure from the main water supply system will not be sufficient to overcome the force that the third biased spring  46  exerts on the third valve disk  47 , and therefore the third valve disk  47  should form a fluid-tight and pressure-tight seal in the high pressure relief valve  17 . When the pressure in the cold water piping system loop  3  and/or the hot water piping system loop  4  exceeds the thrust on the third biased spring  46  in the high pressure relief valve  17 , the third valve disk  47  will open and allow the water pressure in both loops to be suitably relieved through high pressure relief port  48 . 
     Referring to FIG. 2B, there is shown a section elevational view of the cold water circulation pump  19  suitably fixed to the cold water pipe system loop  3 . The water  61  (shown as arrows) flows in a normal direction, and the cold water circulation pump  19  may or may not be energized and operating at this particular time. The cold water circulation pump  19  is shown with an impeller  50  connected to an impeller shaft  51 , a shaft coupling  52  between the impeller shaft  51  and motor shaft  53 , and a pump motor  54 . The pump motor  54  can also be connected to the impeller shaft  51  by a belt drive, a chain drive, or a magnetic drive, by design choice. The pump motor  54  can be an electric motor, an internal combustion engine, a turbine or any other type of prime mover, by design choice. The pump motor  54  can be connected by power line  55  to AC/DC power or solar power; or an internal combustion engine, powered by gasoline, propane, or natural gas can turn the motor shaft  53  directly. Water enters the cold water circulation pump  19  at suction end  56  and leaves at the discharge end  57 . 
     Referring to FIG. 3A, there is shown a combination section elevational view and schematic diagram of the system of the preferred embodiment. The water  61  (shown as arrows) flows from the line pipe  13 , through first isolation valve  14 , through the first check valve  15  in an open mode, through the second check valve  16  in an open mode, past the high pressure relief valve  17  in a closed mode, through the second isolation valve  18 , through the first tee section  58 , through the cold water circulation pump  19 , through the third isolation valve  20 , into the cold water service pipe  21 , and through takeoff valve  59  into the water heater inlet pipe  22 , out through one of the cold water valve outlets (not shown), or through the fourth isolation valve  38  to complete a loop. The water will flow freely when one of the cold water valve outlets is opened or when one of the hot water valve outlets is opened. 
     Referring to FIG. 3B, there is shown a combination section elevational view and schematic diagram of the system of the preferred embodiment in an over-pressure mode. The condition of the system is that the water heater  26  has overheated and the water heater pressure relief valve  35  has malfunctioned (stayed closed or is blocked). The water  61  (shown as arrows) from the water heater  26  has expanded, putting pressure into the hot water pipe system loop  4  and the cold water pipe system loop  3  so that the pressure generated from the overheated water heater  26  is greater than the pressure exerted by the water  61  (shown as arrows) flowing from the main water supply system. The increased water pressure has caused the first check valve  15  and the second check valve  16  to close, thereby preventing any contaminated water from flowing back into the line pipe  13 ; further the water pressure has become so high that it has overcome the thrust of the third biased spring  46 , thereby opening the third valve disk  47  located in high pressure relief valve  17 , allowing overheated water to flow past the third valve disk  47 , and out of the high pressure relief port  48  into an open area or onto the ground. The release of pressurized hot water in this manner will prevent the water heater  26  from exploding and will further prevent any possibly contaminated water from entering the main water supply system. 
     Although the system described in detail has been found to be most satisfactory and preferred, many variations are possible. For example, a second set of check valves and pressure relief valves could be built into the hot water system loop  4 . 
     Although the invention has been described with reference to the preferred embodiment, it will be understood by those skilled in the art that additions, modifications, substitutions, deletions and other changes not specifically described are possible, and that the details herein are to be interpreted as illustrative and not as self-limiting.