Patent Publication Number: US-2007114297-A1

Title: Thermal expansion bleed-off system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application is closely related to and claims priority from U.S. Provisional Application Ser. No. 60/734,421 filed Nov. 8, 2005. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to apparatus for protecting plumbing systems from over-pressurization due to thermal expansion. More particularly, this invention offers an improved system for protecting against over-pressurization of water lines and home hot water heaters connected to a water supply equipped with a back-flow prevention device.  
     BACKGROUND OF THE INVENTION  
      Prior to the conception and development of the present invention, home and building hot water heaters have for many years been equipped with a safety device called a Temperature-Pressure Relief Valve (TPR valve). This prevents an explosion of the tank in the event of overheating or over-pressurization for any reason. One common problem with the TPR valves is leakage when they are older, or when particles get trapped in them due to occasional opening. This latter problem has become more common over the past 20 years due indirectly to changes in building codes and/or plumbing practices.  
      It is commonplace now to have a back-flow preventer or pressure-reducing valve on the total water supply to a house. This prevents any potentially contaminated water from inside the house migrating back into the water main should there be a temporary drop in water main pressure, as might result from a broken water main. Consequently, after a substantial use of hot water in a house followed by no water use for a period thereafter, the cold water that refilled the tank gets heated to the normal hot water tank temperature and that water must expand in volume accordingly. With all avenues of flow closed off now, pressure builds up in the entire water supply system of the house until the set pressure of the TPR valve is reached and it opens to leave water out. These TPR valves are not meant to handle frequent opening and closing. In addition, such openings cause hot water to be spewed out with the potential for scalding someone&#39;s feet or ankles. Even after returning to the essentially closed position, the TPR valve sometimes continues dripping water constantly. As related in U.S. Pat. No. 6,698,714, some residents have responded to this by plugging the TPR outlet pipe thereby creating the very hazardous potential for rupturing the hot water tank.  
      In response to these hazards, building codes and/or plumbing practices have resorted to installing an expansion tank on the cold water inlet line to the water tank. These come in various sizes and typically have a built-in rubber bladder that expands in volume when the water pressure exceeds the normal. Then, when water is used somewhere in the house, the bladder pushes water out to create volume for the next episode of thermal expansion. These expansion tanks are readily available at plumbing supply stores and major home improvement retailers like Lowe&#39;s and Home Depot. Besides their expense, they occupy space near the hot water heater, they place stress on the water lines, and they are subject to failure either by corrosion or decay of the internal rubber bladder. In spite of these drawbacks, there does not appear to be any significant alternatives being offered to homeowners. Hence, there is clearly a need for a better solution to the thermal expansion problem than the expansion tank.  
      Related prior art extends back at least as far as U.S. Pat. No. 1,694,492, which describes a temperature-pressure relief valve for hot water heaters. Such devices were relatively trouble-free until whole-house back-flow preventers became commonplace. In response to the leakage problems that frequently began occurring, expansion tanks emerged as the solution to this relatively new problem. Besides the expense and space occupied by these tanks, they have experienced problems of their own due to corrosion and bladder failures. Hence, there is a need for a less-expensive, longer-lasting replacement for failed expansion tanks.  
      Alternatives to the expansion tank do appear in the prior art. U.S. Pat. No. 4,745,945 teaches a toilet fill valve with an integral pressure relief device. However, fill valves occasionally need replaced, and a plumber or homeowner is likely to overlook this feature as they seek the least-expensive option, and this functionality would often be lost subsequent to initial use. The “Installation Instructions for the Watts Regulator Company&#39;s Model 53 and 30L Pressure Relief Valves” teaches the use of their model  53  as an auxiliary bleeder for thermal expansion relief. Neither of these two references mentions replacement of expansion tanks. In addition, it should be noted that devices like the Watts Model 53 do not come with a tubing connection at the outlet end.  
     SUMMARY OF THE INVENTION  
      According to a first aspect of the invention, in a water piping arrangement having a backflow preventer and a water heater with a standard temperature-pressure relief valve, an auxiliary pressure-relief device is installed in the cold-water supply line to the water heater and this auxiliary relief device is adapted to activate at a pressure slightly below that which activates the temperature-pressure relief device, thereby releasing water and excessive pressure buildup in the piping arrangement due to thermal expansion of water in the water heater. The cold water released is routed via tubing to the floor drain that is in the vicinity of the water heater  
      In a second aspect of the invention, all the necessary pieces for replacing an expansion tank are arranged and offered as a kit.  
     OBJECTS OF THE INVENTION  
      The need for a device or apparatus such an expansion tank in the water feed line to a hot water heater has been well established as forward-only flow home water supply systems have become more common. It is, therefore, one of the primary objects of the present invention to provide an improved and less expensive replacement for a worn-out expansion tank.  
      It is also an object of the invention to provide an improved method of protecting water piping arrangements in new construction.  
      It is also an object of the invention to make the improved method available to homeowners and plumbers in the form of a kit for simple and easy installation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an overview of a hot water heater and piping arrangement showing the auxiliary pressure relief apparatus.  
       FIG. 2  is a close-up side view of an installed thermal expansion bleed valve and the tubing attachment.  
       FIG. 3  is a frontal view of the three-piece kit for replacement of thermal expansion tanks. 
    
    
     DESCRIPTION OF THE PRESENTLY PREFERRED AND ALTERNATE EMBODIMENTS OF THE INVENTION  
      Prior to proceeding with the more detailed description of the present invention it should be noted that, for the sake of clarity, identical components which have identical functions have been designated by identical reference numerals throughout the several views illustrated in the drawings.  
      In  FIG. 1 , an overview the piping and hot water heater arrangement  10  is depicted with the auxiliary pressure bleed-off valve  22  installed in the cold water supply line  18  at the branch tee  20 . A pressure regulator or backflow prevention valve  16  creates the blocked-in situation that leads to the pressure buildup during water heating. Also shown is the temperature-pressure relief device  11  with its outlet drain pipe  14  installed on water heater  36 . The bleed valve drain hose  24  is also shown ending at floor drain  28 . The tubing  24  is prevented from flopping around by clamp  26  attached at one end to rigid drain pipe  14 .  
       FIG. 2  provides a close-up side view of the thermal expansion bleed valve  22  connected to the female threaded connection  20  off of the cold water line  18  with the connection for the plastic tubing  24 .  
      In another aspect of the invention depicted in  FIG. 3 , the invention is assembled into a kit targeted at replacement of expansion tanks. The three main pieces are attached to a printed cardboard backing  30  with plastic straps  32 . The relief valve  22  could be a custom-made unit with the desired cracking pressure and a ¾-inch male NPT inlet connection, and either a ¼-inch or ⅜-inch tubing connection on the other end, and constructed of brass or stainless steel. Alternatively, relief valve  22  could be a slightly adapted version of a commercially available device such as Swagelock Company&#39;s poppet check valve part No. B-4CP2-100. The second part of the kit would typically be about an 8-foot length of either ¼ or ⅜-inch diameter flexible plastic tubing, most likely polyethylene or flexible PVC. The tubing would come with the appropriately sized ferrule  33  and nut  34  already attached to one end. The final piece of the kit would be a clamp to restrain the tubing from excessive movement by supporting it off of the rigid drain line. There are numerous existing designs that would suffice for this purpose, such as simplified versions of standard laboratory thermometer clamps (Fisher Scientific).  
      While a presently preferred and various alternative embodiments of the present invention have been described in sufficient detail above to enable a person skilled in the relevant art to make and use the same, it should be obvious that various other adaptations and modifications can be envisioned by those persons skilled in such art without departing from either the spirit of the invention or the scope of the appended claims.