The TPR valve should meet these requirements:

  1. Be constructed of a plumbing material rated for hot water, typically CPVC, copper, or galvanized steel. PVC and other non-approved plastics should not be used since they can easily melt.

  2. Be the same diameter, or larger, than the supply pipe serving the water heater.

  3. Be as short and as straight as possible so as to avoid undue stress on the valve and installed so that it drains by gravity (downward flow).    

  4. Not be trapped, since standing water may become contaminated and backflow into the drinking water.

  5. Discharge to within 6-inches of the floor, or to a waste receptor with an air gap, or to visible exterior location. It should not be directly connected to the drainage system to prevent backflow, which potentially can contaminate the drinking water.

  6. Not have a valve, T-fitting, or threaded end, to avoid any scenario that might result in a restriction or capping of the discharge piping.

   A properly functioning TPR valve will eject a powerful jet of hot water from the discharge pipe when fully activated, not a gentle leak. If a TPR valve is just leaking slowly, it is an indication that it needs to be replaced. In the rare case that the TPR valve does activate, you should immediately shut off the water and contact a qualified plumber for assistance and repair.

Although most TPR valves never become activated, it is an essential safety component on domestic water heaters. Guidelines concerning these valves and their discharge pipes reflect real hazards that every homeowner should take seriously.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection.

Some material in this blog provided by InterNACHI.


Never, never ever cap the end of a the temperature and pressure relief valve discharge piping like this!

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