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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
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    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? – ThreePhaseEel Dec 21 '17 at 23:45
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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."

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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. – ThreePhaseEel Mar 17 '20 at 4:17

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