TPR drain line connection

Hello, all. I’ve seen this TPR drain line installation on quite a few inspections recently. The TPR drain pipe is connected back to the cold water supply line. Is there a reason for this that supersedes my knowledge as a home inspector? Thanks in adance.

save & memorize
i have input all 14 items into my wh report template & redact whatever isn’t deficient


Unsure with limited view and information, but…

  1. Clue: Has PRV installed which looks to drain to the TPRV drain line.

  2. Does drain line exist to drain or is it connected elsewhere? Where?

That is a whole home pressure relief valve at the top of the pex. But the tprv is not allowed to share with any other drain line

(As jeffrey just beat me to it) :slightly_smiling_face:


No brainer.
Write it up.

It is critical that discharge pipes meet the following requirements, which can be found in InterNACHI’s Water Heater Discharge Piping mini-course, at A discharge pipe should:

  1. be constructed of an approved material, such as CPVC, copper, polyethylene, galvanized steel, polypropylene, or stainless steel. PVC and other non-approved plastics should not be used since they can easily melt.
  2. not be smaller than the diameter of the outlet of the valve it serves (usually no smaller than 3/4").
  3. not reduce in size from the valve to the air gap (point of discharge).
  4. be as short and as straight as possible so as to avoid undue stress on the valve.
  5. be installed so as to drain by flow of gravity.
  6. not be trapped, since standing water may become contaminated and backflow into the potable water.
  7. discharge to a floor drain, to an indirect waste receptor, or to the outdoors.
  8. not be directly connected to the drainage system to prevent backflow of potentially contaminating the potable water.
  9. discharge through a visible air gap in the same room as the water-heating appliance.
  10. be first piped to an indirect waste receptor such as a bucket through an air gap located in a heated area when discharging to the outdoors in areas subject to freezing, since freezing water could block the pipe.
  11. not terminate more than 6 inches (152 mm) above the floor or waste receptor.
  12. discharge in a manner that could not cause scalding.
  13. discharge in a manner that could not cause structural or property damage.
  14. discharge to a termination point that is readily observable by occupants, because discharge indicates that something is wrong, and to prevent unobserved termination capping.
  15. be piped independently of other equipment drains, water heater pans, or relief valve discharge piping to the point of discharge.
  16. not have valves anywhere.
  17. not have tee fittings.
  18. not have a threaded connection at the end of the pipe so as to avoid capping.

Thank you all for the clarification and quick turnaround.