Abstract:
Double cylinder walls are adjustably sealed to an exhaust gas conduit of any of a variety of hot water heating systems. An inner cylinder wall houses a water preheater pipe coil with an inner turbulator coil to circulate source water to be preheated by the exhaust gasses prior to feeding into the water heating system. An outer cylinder wall sealed to the inner cylinder wall prevents exhaust gas leakage from the inner cylinder wall from escaping. Insulation between the cylinder walls retains the heat within the inner cylinder for maximum preheating and an outer cylinder wall that is safe to the touch. A series of valves and pressure and flow gauges control the flow of water and diverts the flow or shuts down the preheater system or the entire hot water heating system as needed for failsafe operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present utility application claims the benefit of provisional application 62/163,094, filed May 18, 2015. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH OR DEVELOPMENT 
       [0003]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates to water heaters and in particular to a universal failsafe water preheater system for preheating input water for any of a variety of hot water heating systems utilized hot exhaust gases from the heating source for preheating the cold water feed into any of the variety of hot water heating systems, providing a water preheater coil inside an insulated double cylinder having an inner cylinder sealed to the exhaust system of the water heating source at one end and sealed to an exhaust pipe or chimney at the other end so that the exhaust gases preheat the water in the coil before it enters the water heating source, wherein the outer cylinder is sealed around the inner cylinder with insulation between cylinders to save heat from escaping, provide an outer surface that is safe to the touch, and provide an outer casing to prevent exhaust gases from escaping into the building should the inner cylinder ever leak any exhaust gases, and including a system of safety valves and gauges to control the circulation of the water through the preheating system with safety shutoffs. 
         [0006]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0007]    Most water heating systems provide hot water by heating up cold water from the water supply source. Prior art systems burn up a substantial quantity of fuel and expel hot polluted exhaust gases into the atmosphere through an exhaust system to maintain a supply of hot water at a desired temperature for users. The user cost for fuel and the environmental impact are huge because of the demand and need for hot water by the entire population. 
         [0008]    While a number of prior art devices provide for preheating feed water into a hot water heater or hot water boiler, none of the prior art devices provide a comprehensive system to insure failsafe operation and control. The prior art systems fail to prevent exhaust gas leaks due to faulty connections or aging of the systems and possible water leaks or low pressure from corrosion and scale build-up in system water pipes. 
         [0009]    U.S. Pat. No. 4,175,518, issued Nov. 27, 1979 to Reames, is for a preheating device for hot water heaters which employs hot gases of combustion from the flue to preheat incoming cold water and to continually preheat water stored in the water tank by natural recirculation. Use of the device provides for increased fuel efficiency because hot combustion gases from the heat source are used for warming of water before venting to the atmosphere, the result being an average increased temperature within the tank so that lesser amounts of fuel are required to reach any desired hot water temperature. 
         [0010]    U.S. Pat. No. 4,043,014, issued Aug. 23, 1977 to Wilson, describes a novel and easy method of construction and assembly which enables a tubular coil to be inserted in an open flue pipe so the flue pipe can be joined; water passing through the coil will recover waste flue heat from furnaces and boilers. 
         [0011]    U.S. Pat. No. 7,360,507, issued Apr. 22, 2008 to Logsdon, indicates an energy saving apparatus attached to a standard gas-powered water heater. All gas-powered water heaters typically have an air vent which vents hot air from the water heater. The apparatus takes advantage of this fact by routing a cold water inlet line into a heating coil wrapped around the air vent, with the heating coil eventually being connected to an outlet water line that then enters the hot water heater. The heating coil is merely a water line located in between the cold water inlet line and the outlet water line that is wrapped around the air vent many times. The heat from the air vent will transfer some of its heat to the water circulating within the heating coil, causing the hot water heater to utilize this otherwise wasted energy and subsequently causing the hot water heater to need less energy to heat the water within the hot water heater. 
         [0012]    U.S. Pat. No. 2,521,462, issued Sep. 5, 1950 to Kinzelmann, claims a domestic hot water heater adapted to utilize a large amount of the heat now wasted by going up the chimney from the usual fire of a water heating or house-heating unit. 
         [0013]    U.S. Pat. No. 4,335,850, issued Jun. 22, 1982 to Kreps, claims a system for producing hot water for a residential dwelling by recovering heat from the hot combustion gases in the flue and chimney of the dwelling&#39;s heating system. The system uses the usual hot water tank and furnace of the dwelling without any substantial modifications thereto. The hot water tank is located in an upper floor of the dwelling and is connected to the furnace which is located on a lower level by a first section of pipe which extends from adjacent the water heater to the furnace flue within the chimney. A cold water supply is connected to the first section of pipe by a second section of pipe which also extends through a portion of the chimney and the furnace flue to recover heat from the hot combustion gases passing therethrough. The heated water in the sections of pipe flows into the hot water tank through the usual cold water inlet line for subsequent discharge from the tank throughout the house. The usual heating means of the hot water tank supplies any additional heat that may be required to heat the water in the tank to a preset temperature during the summer or during periods of lower furnace usage. 
         [0014]    U.S. Pat. No. 8,091,514, issued Jan. 10, 2012 to Jimenez, indicates an energy re-claimer for preheating water prior to the water entering a conventional residential, commercial or industrial gas water heater. The energy re-claimer is mounted on top of the water heater between the draft diverter and the hot air flue. The energy re-claimer is preferably a double wall construction that is larger in diameter than the draft diverter and hot air flue in order to allow normal passage of hot air through the system; however, a single wall construction may also be used. Tap water enters a pipe inside the double wall construction and is heated prior to being directed through the water heater. The pipe may be constructed of a number of straight lengths connected by returns or may be in the form of a single straight section connected to a coil made of connected curving sections that surround the axis of the energy re-claimer. A condensation collector may be provided between the draft diverter and the energy re-claimer to collect any condensation that may form as a result of cooling gases and prevent the condensate from falling into the water heater where it could extinguish the flame. 
         [0015]    U.S. Pat. No. 3,987,761, issued Oct. 26, 1976 to Downs et al, provides an auxiliary water heating tank to be employed in combination with a conventional tank water heater which is gas fired and supplies heated flue gases to the ambient, the heated flue gases from the water heater to be supplied either into a flue pipe centrally located within the auxiliary heater tank or into a chamber surrounding the auxiliary heater tank, the first embodiment employing a plurality of heat conducting members extending transversely through said flue pipe with the ends of such extending within the auxiliary heater tank, the heating conducting members arranged in a spiral pattern throughout said flue pipe, the members adapted to conduct heat energy from said flue pipe into water contained within said auxiliary heater tank, the second embodiment employing heat sinks and the principle of thermosyphon to efficiently heat the water, the third embodiment conducting the exhaust gases of the water heater into a chamber totally encompassing the auxiliary heater tank. 
         [0016]    U.S. Pat. No. 4,037,567, issued Jul. 26, 1977 to Torres, shows a water heating system including a boiler which is connected with a source of water supply for receiving water under pressure. An exhaust flue is connected to the boiler for the discharge of gaseous products of combustion. A pair of concentrically arranged coils is positioned within the exhaust flue and is connected with the conduit feeding water to the boiler. A recycle loop is thus provided for withdrawing a minor portion of the water being fed to the boiler and for recycling same at a higher temperature to the feed conduit. The water circulates within the loop by natural connection. 
         [0017]    U.S. Pat. No. 4,373,473, issued Feb. 15, 1983 to Grandmont, describes a heat recuperating water heating system including a water receiving enclosure to which is mounted a burner to provide a source of heat to the water and the products of combustion from this heat source are carried through a flue which is modified to include a manifold equipped with a continuous doubly wound coil defining inner and outer concentric loops, in turn, connected to a pair of conduits; a water circulator is mounted in one of the conduits and is electrically connected to the burner so that each time the burner operates, the circulator is also set in operation and provides a constant determined flow of water in the coil. 
         [0018]    U.S. Pat. No. 6,564,755, issued Mar. 20, 2003 to Whelan, discloses a heat recovery system including a heat exchanger surrounding a flue pipe from a furnace for preheating water. The heat exchanger includes a sleeve surrounding the flue pipe to define an annular space and form a water jacket in direct contact with the flue pipe. Several water storage tanks are connected in series and mounted around the sleeve to absorb heat from the water jacket. The outer water tanks are connected to one end of the water jacket at the downstream end of the flue pipe so that water is carried sequentially through each of the water tanks and through the water jacket surrounding the flue pipe. Typically, the water jacket includes a plurality of baffles to define a tortuous path through the water jacket. A conduit for supplying water to the outer water tanks can be wrapped around the downstream end of the flue pipe in a spiral manner to preheat the water prior to feeding to the water tanks. The preheated water exiting the upstream end of the water jacket can also pass through a conduit that is wrapped around the flue pipe in a spiral fashion to further heat the water before directing to a conventional water heater or domestic water supply. 
         [0019]    U.S. Pat. No. 2,143,287, issued Jan. 10, 1939 to Smith, concerns an improved heat exchange coil which permits of free and rapid circulation of liquid within the coil and presents the greatest area of contact to the hot gases, and which may be placed in the combustion chamber of a furnace or in the flue to utilize the waste heat in the flue gases. The invention makes possible the extraction of much of the waste heat to heat water either for domestic purposes or to supplement the main heating system. 
         [0020]    U.S. Pat. No. 4,215,741, issued Jan. 5, 1980 to Averbuch et al, is for a heat exchanger operatively arranged, like a sliding drawer in a dresser, to be urged through opposite direction sliding movement to facilitate its positioning at and removal in relation to a heat exchange station within a flue, or the like, of a heating system, with the result that it is readily easy to service and maintain the unit clear of soot and other clogging materials. Since, as noted, the problems associated with clogging are significantly obviated, the heat exchanger, among other advantages, can embody in its construction closely spaced heat exchange fins to greatly enhance the amount of heat extracted from the exiting flue gases. 
         [0021]    U.S. Pat. No. 4,412,526, issued Nov. 1, 1983 to DeGrose, claims a water tempering system for preheating water comprising a storage tank for tempered water; a water tempering unit containing S-shaped heat exchange tubes positioned in the exhaust flue of a furnace; first conduit means for conveying water from the storage tank to the tempering unit; and second conduit means for conveying water from the tempering unit to either the storage tank or an outlet tube for the water tempering system. 
         [0022]    U.S. Pat. No. 4,702,226, issued Oct. 27, 1987 to Shelley, describes a preheater for a conventional gas-fired water heater having an outer container, an inner reservoir, water conduits in fluid communication with the reservoir and openings in the outer container allowing the through passage of hot exhaust flue gas from a conventional hot water tank to have an increased residence time with respect to the reservoir for efficient heat transfer of the hot flue gases. The heated water is fed from the preheater to the hot water tank on demand. The preheater is placed atop the hot water tank to receive the hot flue gases therefrom. 
         [0023]    U.S. Pat. No. 3,916,991, issued Nov. 4, 1975 to Trump, is for a heating system for use with a primary source of heat, such as a gas hot air furnace, or the like. A first conduit formed with perforations therethrough conveys hot exhaust gases generated by the furnace to a flue. A second conduit carrying a fluid is coiled about the first conduit in close proximity thereto so as to permit a transfer of heat to said fluid from exhaust gases escaping from said perforations and contacting said second conduit. A third conduit houses the first and second conduits and conveys exhaust gases that have escaped through said perforations to the flue. Sleeve means intermediate the first and second conduits control the rate of said heat transfer. 
         [0024]    U.S. Pat. No. 1,766,080, issued Jul. 24, 1930 to Marks, provides means whereby fluid can be heated efficiently by waste products of combustion through intimate contact with extended surfaces exposed to the action-of the heating gases. In its preferred form, it comprises a casing with undulated exterior walls and having internal flues alternating with the exterior fissures or sulci between the lobes or ridges formed by the wall undulations. The undulated walls and the internal flues passing through the expanded sections of the casing form sinuous channels for the flow of fluid, preferably transverse to the direction of flow of products of combustion passing through the internal flues and external fissures. Such casing is preferably combined with a plurality of hollow primary heating units having between them passages through which products of combustion are discharged from a combustion chamber to the fines and fissures of the casing. Water heaters embodying the present invention are particularly adapted for use in preheating water-applied to a heating system or for heating an auxiliary supply of water, as for household use or the like. 
         [0025]    U.S. Pat. No. 1,065,837, issued Jun. 24, 1913 to Reichhard, puts forth a preliminary hot water heater having a shell and water-circulating means within the shell, the shell being interposed in the smoke flue of the ordinary hot water heater to cause the products of combustion of the ordinary hot water heater to, circulate through the shell with a view to heat the water passing through the said water-circulating means, the latter being connected at one end with a source of water supply and being connected at the other end with the inlet to the water compartment of the ordinary hot water heater. 
         [0026]    U.S. Pat. No. 685,835, issued Nov. 5, 1901 to Groh, puts forth a combined stove and water-heater especially adapted for use in engine-houses, livery-stables, and similar places where an occasional use of hot water is necessary, but where it is not desirable or convenient to maintain a constant supply of the same. 
         [0027]    What is needed is a comprehensive failsafe system of utilizing wasted heat from the water heater exhaust system to pre-heat supply water before it enters the water heater chamber using a failsafe water pre-heater system having sealed double cylinder walls to prevent exhaust leakage into the building, with insulation between the cylinder walls to retain the heat within the inner cylinder and maintain the outer cylinder wall at a temperature that is safe to the touch, providing a turbulator inside the preheater coil inside the inner cylinder for increased heat transfer from the exhaust gases to the preheated water, and including a series of shutoff valves and gauges to control the flow of water as needed and to prevent damage from any malfunctions in the system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0028]    An object of the present invention is to provide universal failsafe water preheater system for preheating input water for any of a variety of hot water heating systems utilized hot exhaust gases for preheating the cold input water from a water supply prior to feeding the water into a water heating source, the system comprising sealed double cylinder walls with the inner wall housing at least one preheater water coil having an internal turbulator for increased turbulence and friction of the water preheating in the coil to enhance heat transfer, the inner cylinder sealed to the exhaust system and the outer cylinder wall sealed to the inner cylinder wall to prevent exhaust leakage into the building, with insulation between the cylinder walls to retain the heat within the inner cylinder and maintain the outer cylinder wall at a temperature that is safe to the touch. 
         [0029]    Another object of the present invention is to provide a series of shutoff valves and pressure gages and flow gauges to control the flow of water as needed through the preheating system and to shut down various parts of the system or the entire system when a malfunction is detected to prevent damage to the system and to stop any water leakage. 
         [0030]    In brief, the present invention provides a water pipe coil inside a double-walled insulated housing adapted to be installed in place of a removed section of a gas exhaust pipe from any of a variety of heating sources for hot water to preheat the feed water input into the heating source. The system includes an inlet valve and pipe from the cold water supply into the preheating coil and an outlet valve from the preheating coil to admit the preheated water into the heating source for the hot water. 
         [0031]    The present invention being installed in the exhaust gas system reuses the energy already being spent to heat the hot by using the exhaust gasses to preheat the feed water input into the heating source for the hot water so that less energy is needed to get the input feed water up to the desired temperature for hot water usage. 
         [0032]    The present invention is using the hot temperature of the exhaust gasses to flow over the copper heating coil of the present invention, preheating the cold feed water input to go through the copper coil first so that when there is a demand to heat the hot water, an outlet valve from the preheater coil will release the preheated water into the heating source for the hot water. 
         [0033]    The insulation and the gap (which may be approximately one-inch) between the cylinder walls of the present invention would retain heat within the inner chamber and maintain the outer cylinder wall at a low temperature so that the cylinder unit would not burn someone touching the outer cylinder wall. 
         [0034]    A plurality of valves insure the failsafe operation of the system of the present invention. 
         [0035]    One of the plurality of valves comprises at least one water flow bypass valve for opening water flow from the water supply through the water preheater element as desired and for closing water flow from the water supply through the water preheater element to allow the water from the water supply to flow directly into the water heating tank. 
         [0036]    Another of the plurality of valves comprises a relief valve in a cold water supply input line leading into the water preheater element of the present invention, the relief valve adapted to measure water pressure of water entering the water preheater element and adapted to shut off the heater source or water preheater system upon a loss of water pressure signaling a blockage in the water preheater element, which may be due to scale up causing pressure loss. 
         [0037]    Another of the plurality of valves comprises a low flow pressure valve in a preheated water outlet from the water preheater element of the present invention, the low flow pressure valve adapted to measure water pressure of the preheated water leaving the water preheater element so that in the event of water pressure decrease indicating a water leak in the water preheater element the low flow pressure valve will shut down the water preheater system. 
         [0038]    The primary purposes and advantages of the present invention are to save gas, save emissions, and save customer costs by reusing the energy already being spent on heating the water heater tank by installing the present invention in the exhaust gas system with the water supply feed water circulating through the preheater coil of the present invention exposed to the exhaust gases so that the exhaust gases preheat the water entering the water heater tank or boiler to require less gas and energy to bring the preheated water up to the desired temperature. 
         [0039]    An advantage of the present invention is that it provides a double walled cylinder with the inner cylinder sealed to the exhaust system and the outer wall sealed to the inner wall to prevent leakage of the exhaust gases should the inner cylinder fail. 
         [0040]    Another advantage of the present invention is that it provides an insulated space between the cylinders to retain heat therein and maintain an outer surface that is safe to touch. 
         [0041]    An added advantage of the present invention is that it provides at least one turbulator maximizing friction inside at least one preheater coil shaped for optimum heat transfer between the exhaust gases and the preheated water in the coil. 
         [0042]    An ensuing advantage of the present invention is that it provides a series of valves and controls to close off the preheater coil in the event of a blockage or leak in the preheater coil and shut down the system in the event of a system failure. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0043]    These and other details of the present invention will be described in connection with the accompanying drawings, which are furnished only by way of illustration and not in limitation of the invention, and in which drawings: 
           [0044]      FIG. 1  is a perspective view of the water preheater system of the present invention installed in the water heater exhaust pipe and the water pipes connecting between the a water supply through the preheater and into the water heater tank showing the water control valve and safety shut-off valves; 
           [0045]      FIG. 2  is a perspective view in partial section of the water preheater system of the present invention aligned for installation in the water heater exhaust pipe and the water pipes aligned for connecting between the water supply through the preheater coil and into the water heater tank showing the water control valve and safety shut-off valves and showing the double cylinder walls and insulation therebetween, the interior water preheater coil, and a portion of the turbulator inside the water preheater coil; 
           [0046]      FIG. 3  is a perspective view in partial section of the water preheater system of  FIG. 2  installed in the water heater exhaust pipe and the water pipes connected between the water supply through the preheater coil and into the water heater tank showing the water control valve and safety shut-off valves and showing the double cylinder walls and insulation therebetween, the interior water preheater coil, and a portion of the turbulator inside the water preheater coil; 
           [0047]      FIG. 4  is an elevational diagrammatic view in partial section of the water preheater system of the present invention installed on a boiler furnace exhaust gas pipe showing a heat exchanger in the boiler furnace which heats the hot water stored in a separate hot water holding tank, the boiler furnace heating water passing through the heat exchanger or heat exchanging coil from a water heating input pipe from the hot water holding tank and hot water flowing from the heat exchanging means through a hot water output pipe from the boiler furnace into the hot water holding tank, wherein the preheated water from the water preheater system flows into the water heating input pipe from the hot water holding tank into the heater exchanger in the boiler furnace and showing the water control valves and safety shut-off valves; 
           [0048]      FIG. 5  is an elevational diagrammatic view in partial section of the water preheater system of the present invention installed in an indirect water tank heating system having a heating source comprising a boiler furnace separate from the indirect water heating tank, the indirect water heater tank comprising a water heating element inside the indirect water tank communicating with the boiler by a water heating input pipe feeding from the boiler furnace into the water heating element to heat the water in the indirect water heater tank and further communicating with the boiler by a water return pipe from the water heating element back into the boiler for reheating and the boil further comprising a boiler exhaust gas pipe, a portion of the boiler exhaust gas pipe being replaced by the double-walled insulated sealed housing having the inner chamber conducting the exhaust gasses through the inner chamber to contact the water preheater element housed therein transferring heat to the preheater water flowing through the water preheater element and further comprising a preheated water pipe feeding from the preheater element into the water return pipe leading into the boiler; 
           [0049]      FIG. 6  is an elevational diagrammatic view in partial section of the water preheater system of the present invention installed in a tank-less hot water heating system having a boiler furnace heating a hot water coil for on demand hot water; showing the hot water coil heat exchanging means in the boiler furnace which receives a water supply source fed into the boiler furnace through a water heating input pipe to the heat exchanging means and further comprising a heated water output pipe from the boiler furnace heat exchanging means feeding the hot water supply pipes directly, and showing a portion of the boiler exhaust gas pipe replaced by the double-walled insulated sealed housing having the inner chamber conducting the exhaust gasses through the inner chamber to contact the water preheater element housed therein transferring heat the preheater water flowing through the water preheater element and further comprising a preheated water pipe feeding from the preheater element into the water heating input pipe into the boiler; 
           [0050]      FIG. 7  is an elevational diagrammatic view in partial section of water preheater system of the present invention installed in a stand-alone tank-less water heater, showing a heat exchanging means, which may be a coiled copper water heater pipe communicating with a heater for heating water from a water supply source fed into the stand-alone tank-less water heater through a water heating input pipe to the heat exchanging means and further comprising a heated water output pipe from the stand-alone tank-less water heater heat exchanging means feeding the hot water supply pipes, and showing a portion of the stand-alone tank-less water heater exhaust gas pipe being replaced by the double-walled insulated sealed housing of the present invention having the inner chamber conducting the exhaust gasses through the inner chamber to contact the water preheater element housed therein transferring heat the preheater water flowing through the water preheater element and further comprising a preheated water pipe feeding from the preheater element into the water heating input pipe to the heat exchanging means. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0051]    In  FIGS. 1-7 , a universal failsafe water preheater system  10  for preheating input water for any of a variety of hot water heating systems utilizes hot exhaust gases for preheating input water for a water heater source utilizing a preheater coil  20  inside a double walled sealed cylinder  30  installed in the water heating source exhaust pipe  56 A and  56 B,  86 A and  86 B,  96 A and  96 B of any of heating sources  50 ,  80 , and  90 . The system of the present invention is adapted for receiving hot exhaust gases from the water heating source flowing through an interior of the double cylinder  30  encircling and flowing along the length of the preheater coil  20  for preheating input water flowing from a water supply pipe  40 A through the preheater coil  20  and out through a preheater water supply pipe  22  into the water feed pipe  40 B,  81 A,  81 B, and  91  to the water heating source. 
         [0052]    In  FIGS. 1, 2, and 3 , a double-walled insulated sealed preheater housing  30  is adapted for replacing a section of a water heater exhaust gas pipe  51 A and  51 B. The preheater housing  30  comprises an inner wall  38  housing an inner chamber  32  having a hollow interior and two end openings having end connectors  18 A and  18 B or  19 A and  19 B communicating with an interior passageway of the exhaust gas pipe to admit the exhaust gasses to pass from a first section of the exhaust gas pipe  51 A through the inner chamber  32  to a second section  51 B of the exhaust gas pipe. The two end connectors  18 A and  18 B or  19 A and  19 B having adjustable exhaust gas sealing connectors adapted for sealing with the two sections of the exhaust gas pipe  51 A and  51 B respectively, to prevent exhaust gasses from escaping. 
         [0053]    In  FIGS. 2 and 3 , the preheater housing further comprises an outer wall  37  spaced apart from and sealed to the inner wall  38  adjacent to each end of the inner wall, the outer wall  37  adapted to seal in any exhaust gasses which might escape from the inner wall  31  for a failsafe system. At least one layer of heat insulation  31  between the inner wall and the outer wall serves to retain heat within the inner chamber  32  making the system more efficient and to maintain the outer wall  37  at a temperature which is safe for human contact. The inner wall  38  and outer wall  37  of the double walled sealed insulated housing are preferably separated by at least one inch all around. 
         [0054]    The water preheater element  20 , preferably a copper coil water pipe or other shape for maximum heat transfer from the exhaust gases, is adapted to be attached between a water supply source, such as a water supply pipe  40 A and a water inlet pipe  40 B to a water heater tank  50  to receive water passing through the water preheater element between the water supply source  40 A and the water inlet  40 B to the water heating tank  50  for preheating the water to feed into the water heater tank. The water preheater element is installed inside the inner chamber  32  with at least one sealed connector  23 A and  23 B, the water preheater element  20  extending along a substantial portion of the inner chamber  32 . The water preheater element  20  is adapted to receive the heat from the exhaust gasses to preheat the water prior to entering the water heater tank  50 . 
         [0055]    The water preheater element  20  preferably comprises a water pipe shaped into a configuration to occupy a substantial portion of the inner chamber  32  while allowing maximum flow of exhaust gasses around the water preheater element  20  to preheat the water therein while still allowing natural exhausting of the exhaust gasses through the exhaust gas pipe  51 B. The water preheater element  20  preferably comprises a copper water pipe structured in a cylindrical coil pipe configuration aligned with and separated from the inner wall  31  along the length of the inner chamber  32 . 
         [0056]    The water preheater element  20  has at least one inlet pipe  21  from the water supply pipe  40 A into the water preheater element  20  and at least one preheated water outlet pipe  22  from the water preheater element  20  passing through the housing walls  37  and  38  with at least one air-tight seal therebetween  23 A and  23 B, the preheater water outlet pipe  22  communicating with a water heater input pipe  40 B into the water heating tank  50 . Depending on the water preheater element configuration, both the at least one water supply inlet pipe  21  and at least one preheater water supply outlet pipe  22  may both pass through a single opening through the housing walls  37  and  38  with an air-tight seal therebetween similar to the two air-tight seals  23 A or  23 B, when the preheater element is shaped with both the water supply pipe  21  and the preheater water outlet pipe  22  side-by-side passing through a single sealed opening through the housing walls  37  and  38 . 
         [0057]    The water preheater element  20  preferably further comprises an internal means to add more friction to water flowing within the water preheater element, preferably a turbulator  47 , as shown in  FIGS. 2 and 3 , to increase the turbulence and friction of the flowing water to further increase the heat transfer from the exhaust gasses flowing through the inner chamber  32  to the water flowing within the water preheater element  20 . 
         [0058]    The turbulator  47  preferably comprises at least one coiled spring fit into at least a portion of the cylindrical coil pipe or the entire preheater element  20 . The at least one coiled spring turbulator  47  is preferably fabricated of coiled copper nickel in a spiral coil configuration having a diameter less than the inner diameter of the water preheater element  20  coil pipe to allow full contact of the preheater water with the wall of the water preheater element coil pipe for maximizing heat transfer to the preheater water from the exhaust gasses. 
         [0059]    A plurality of safety valves and controls create a failsafe system. In the event of increasing water pressure at safety relief valve  25  and pressure gauge  28  in the preheater water inlet pipe  21  to the water preheater element, due to blockage of water flow through the water preheater element  20 , the safety relief valve  25  is adapted to shut off the water heating tank  50  upon an increase of water pressure signaling a blockage in the water preheater element  20 . In the event of water pressure decrease in the safety low pressure valve  26  in the preheated water outlet pipe from the water preheater element  20 , due to leakage of water flow through the water preheater element, the low flow switch  26  is adapted to shut down the water preheater system using ball valves  24  and opening the bypass ball valve  24 A to bypass the water peheater system and allow water flow from the water supply  40 A pipe to flow directly into the water heater tank  50  through the normal water inlet flow pipe  12  and the water heater input pipe  40 B. 
         [0060]    In  FIGS. 1-3 , the water heating tank  50  comprises a gas water heater tank having an exhaust gas pipe  51 A and  51 B, a portion of the exhaust gas pipe being replaced by the double-walled insulated sealed preheater housing  30  having the inner chamber  32  conducting the exhaust gasses through the inner chamber to contact the water preheater element  20  housed therein transferring heat from the exhaust gases to the preheater water flowing through the water preheater element  20 . 
         [0061]    In  FIG. 4 , the water heating source comprises a boiler furnace  80  separate from a hot water holding tank  50 A. The boiler furnace heats hot water for the hot water supply as the water flows through a heat exchanger  85  or heat exchanging coil from a water heating input pipe  81 A from the hot water holding tank  50 A and the hot water flows from the heat exchanging means  85  through a hot water output pipe  82 A from the boiler furnace  80  into the hot water holding tank  50 A. The boiler furnace further comprises a boiler exhaust gas pipe  86 A and  86 B. A portion of the boiler exhaust gas pipe is replaced by the double-walled insulated sealed housing  30  of the water preheater system of the present invention. The exhaust gasses pass through the inner chamber within the inner wall as indicated in  FIGS. 2 and 3 , to contact the water preheater element  20  housed therein transferring heat to the input water flowing through the water preheater element  20 . The preheated water flows through a preheated water pipe  40 B feeding from the preheater element  20  into the water heating input pipe  81 A to the heat exchanging means  85  in the boiler furnace  80 . 
         [0062]    In  FIG. 5 , the water heating source comprises a boiler furnace  80  for a forced hot water radiator heating system separate from an indirect hot water heating tank  50 B. The indirect hot water heating tank  50 B comprises a hot water heating element  89 , preferably a coiled copper water pipe, inside the indirect hot water heating tank  50 B communicating with the boiler furnace by a hot water heating input pipe  82 B feeding from a forced hot water heating system pipe  83  from the boiler furnace  80  into the hot water heating element  89  to heat the water in the indirect hot water heater tank  50 B for output through the hot water supply pipe  60 . The hot water heating element  89  further communicates with the boiler furnace  80  by a water return pipe  81 B from the hot water heating element back into the boiler furnace  80  for reheating. A return pipe  84  from the building forced water heating system also feeds back into the boiler furnace. 
         [0063]    The boiler furnace  80  further comprises a boiler exhaust gas pipe  86 A and  86 B, a portion of the boiler exhaust gas pipe being replaced by the double-walled insulated sealed housing  30  of the water preheater system of the present invention. Cold input supply water flows from the water supply  40 A pipe through the water preheater element  20  of the inner chamber and is preheated by the exhaust gases flowing through the inner chamber  32 , as shown in  FIGS. 2 and 3 . A preheated water pipe  40 B feeds the preheated water from the preheater element  20  of the present invention into the indirect hot water heating tank  50 B. 
         [0064]    In  FIG. 6 , the heating source comprises a boiler furnace  80  heating a heat exchanger or heat exchanging coiled pipe  87  of a tank-less hot water heating system. A system feed water supply input pipe  40 A sends water through the heat exchanging coiled pipe  87  to heat the water for the hot water to flow out directly through the hot water supply output pipe  60  into the hot water pipes for use, providing an on demand tank-less hot water system. The boiler furnace  80 , in a separate piping system provides forced hot water heating to radiators through a forced hot water heating output pipe  83  and a return pipe  84 . 
         [0065]    The boiler furnace further comprises a boiler exhaust gas pipe  86 A and  86 B, a portion of the boiler exhaust gas pipe being replaced by the double-walled insulated sealed housing  30  of the water preheater system of the present invention. Cold source water through the water supply pipe  40 A is diverted through the water preheater element  20  in the inner chamber  32 , as shown in  FIGS. 2 and 3 , and preheated by exhaust gases flowing through the inner chamber  32 . The preheated water flows from the water preheater element  20  through a preheated water pipe  40 B and furnace input pipe  81 A feeding through the heat exchanging coiled pipe  87  to heat the water for the hot water to flow out directly through the hot water supply output pipe  82 A and into the hot water pipe  60  system for use. 
         [0066]    In  FIG. 7 , the heating source comprises a gas heater  100  in a stand-alone on demand tank-less hot water heating system  90 . The stand-alone tank-less water heater  90  comprises a heat exchanging means  97 , which may be a coiled copper pipe, communicating with the heater  100 , which may be a gas heater and may have a fan or blower associated with the gas heater. The stand-alone tank-less water heater  90  heats water from a water supply source pipe  40 A fed into the stand-alone tank-less water heater  90  through a hot water heating input pipe  91  to the heat exchanging means  97 . 
         [0067]    The stand-alone tank-less water heater further comprises a stand-alone tank-less water heater exhaust gas pipe  96 A and  96 B, a portion of the stand-alone tank-less water heater exhaust gas pipe being replaced by the double-walled insulated sealed housing  30  of the present invention. Exhaust gasses flow through the inner chamber contacting the water preheater element  20  housed therein to transfer heat to the preheater water flowing through the water preheater element, as shown in  FIGS. 2 and 3 . The preheated water flows out from the water peheater element through a preheated water pipe  22  into the water heating input pipe  40 B and the hot water heating input pipe  91  to the heat exchanging means  87  of the stand alone tank-less water heater to heat the water for the hot water to flow out directly through the hot water supply output pipe  82 A and into the hot water pipe  60  system for use in the tank-less hot water supply on demand hot water system. 
         [0068]    All of the systems in  FIGS. 4-7  provide the same plurality of safety valves and controls to create a failsafe system, as shown in  FIGS. 1-3 . 
         [0069]    In use, a failsafe double walled housing  30  of the water preheater system  10  of the present invention is installed in an exhaust gas pipe of any of a variety of sources of heat for a hot water heating system with failsafe adjustable sealed connections  18 A and  18 B. 
         [0070]    The present invention provides a water pipe coil  20  inside a double-walled insulated housing  30  adapted to be installed in place of a removed section of a gas exhaust pipe from any of a variety of heating sources for hot water to preheat the feed water input into the heating source. The system includes inlet valves  24  and  25 , gauge  28 , and inlet pipe  21  from the cold water supply pipe  40 A into the preheating coil  20  and an outlet valve  24 , flow switch  26 , and outlet pipe  22  from the preheating coil  20  to the heating source inlet pipe  40 B to admit the preheated water into the heating source for the hot water forming a bypass of the normal flow of cold water to the heating source for the hot water. The preheater system will automatically shut down in case of a system failure to allow the cold water to flow normally into the heating source, or the entire hot water heating system may be automatically shut down for emergency failures of the system. 
         [0071]    The present invention being installed in the exhaust gas system reuses the energy already being spent to heat the hot by using the exhaust gasses to preheat the feed water input into the heating source for the hot water so that less energy is needed to get the input feed water up to the desired temperature for hot water usage, which also lowers emissions and lowers operating costs. 
         [0072]    The present invention is using the hot temperature of the exhaust gasses to flow over the copper heating coil of the present invention, preheating the cold feed water input to go through the copper coil first so that when there is a demand to heat the hot water, an outlet valve from the preheater coil will release the preheated water into the heating source for the hot water. 
         [0073]    The insulation  31  and the gap (which may be approximately one-inch) between the cylinder walls  37  and  38  of the present invention would retain heat within the inner chamber  32  and maintain the outer cylinder wall at a low temperature so that the cylinder unit would not burn someone touching the outer cylinder wall  37 . The outer cylinder  37  contains the exhaust gases in case of a failure or leak of the inner cylinder  38 . 
         [0074]    The plurality of valves, pressure and flow gauges, and double walled sealed preheater system insure the failsafe operation of the preheater system of the present invention, which is adapted to be used with any of a variety of hot water heating systems. 
         [0075]    It is understood that the preceding description is given merely by way of illustration and not in limitation of the invention and that various modifications may be made thereto without departing from the spirit of the invention as claimed.