Pressure Relief Valve Plumbing in 2015 UPC

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Zane Bridgers

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Northern New Mexico - Climate Zone 5A
Hi everyone -

I was wondering what the 2015 UPC mandates for plumbing from a tank water heater’s pressure relief valve?

I believe this is addressed in the 2015 UPC Chapter 6
Section 608.5 Discharge Piping

As I understand, a pan is no longer approved: “Discharge from a relief valve into a water heater pan shall be prohibited.”

The piping must be approved for high heat (no regular pvc).

It must empty into a drain system separate from the dwv system or drain outside.

It must have an air gap before draining outside in cold climates.

Must not drain where it can cause injury.


So, since we are slab on grade and don’t have a drain, how does an outside drain look with the air gap? Does the WH drain to a pain which then drains outside?

What kind of fittings go outside?

The WH is on an exterior wall that separates it from the front porch. Seems this might not be an approved drainage location?

Thank you all very much! I hope this can help others as well!


In the Trades
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In my city, most WHs are located in garages, so we use 3/4" metal pipe from the T&P valve to the outside. Drain pipe has to end no higher than 6" above grade.
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