I had a plumber install a new water heater the other day, and he said it's up to 2018 (US) code, but I've been wondering if the T&P relief valve discharge pipe really is correct, because it seems to me like discharge pipes shouldn't flow upwards:

discharge pipe

The hole in the wall that the discharge pipe goes out of is the one used by the original water heater's pipe, and I don't know why they made it so high - I'm guessing because there's not a lot of room in this corner of my garage and they needed the pipe to go above the water heater.

  • If the pipe is ever used it's because there's high pressure in the heater. Gravity isn't really a concern. Where does the brass fitting go that is cut off at the bottom of the photo?
    – isherwood
    Dec 21 '17 at 20:29
  • @isherwood it's capped off at the bottom; I'm guessing it's just used as an elbow?
    – seand
    Dec 21 '17 at 20:34
  • 1
    Probably a drain since that's the low point on this side.
    – isherwood
    Dec 21 '17 at 21:01
  • Ah yeah, that makes sense.
    – seand
    Dec 21 '17 at 21:05
  • Can you post a photo of where the other end of that silly tee fitting goes? Dec 21 '17 at 23:45

Illegal. Your photo shows a TPV outlet pipe with a trap. Last I checked, UPC 608.5 says "No part of such drain pipe shall be trapped ..."
Similarly, IPC (2012) 504.6 (8) Discharge piping serving a TPV shall "Not be trapped."


Majority of water heater are located where the relief line has no option other than going up and then to outside wall where it drops to go outside at a safe height low off the ground. However this requires a drain by the water heater at the lowest point before rising up. The brass fitting in the picture has a plug that can be removed to drain the relief line after a discharge.

  • Do people not have floor drains or sumps that the T&P discharge can be routed to? What you're describing sounds like blatant and widespread ignorance of the applicable Code on this subject -- see IRC P2804.6.1 for details. Mar 17 '20 at 4:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.