Pressure relief valve (T&P) plumbing with PEX?

[Cap'n Jan]

The current plumbing for my electric (tank) hot water heater is byzantine. (See pic)

I want to cut out all the old corroded copper overflow setup and plumb to the wall connection with PEX (and sharkbite fittings)

Question: Is it 'safe' to plumb the new T&P valve using standard (red) PEX 3/4 pipe and sharkbite connectors? The T&P relieves at 210 degrees and PEX is 'good for' 200. Seems that it would be alright, but need an expert.

1. Safe to do ( but everyone may point and laugh.)
2. Pretty safe to do
3. STUPID AND TOTALLY UNSAFE TO DO.
4. Go ahead and plumb with PEX, paint it with 'copper' spray paint and call it done!

Pick a number or add a comment!

See picture for the (****) story that is my current T&P setup.

 

[Reach4]

I am not a plumber. I think most places this is not permitted. I think it would be safe, but that does not matter.

What I can say is that this a great use for galvanized pipe. Everybody allows it. Nobody will laugh.

 

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[Jadnashua]

Pex is rated for up to 180-degrees (of those I have looked at). The T&P doesn't open until the water gets to 210-degrees. IMHO, it's neither safe nor smart.

 

[Phog]

I'm going to go with choice "2". I think it'll work fine. But I agree that it won't meet code.

There are at least 3 different types of standard PEX - types A, B, and C. (There is also oxygen barrier PEX, sometimes called PEX-Al-PEX). There are differences in the fabrication process which leads to different characteristics. There are also differences in ratings between manufacturers even for the same "type".

The temperature rating is a function of pressure. PEX-A is usually the highest quality (for example Uponor brand) and this is what the 200F @ 80psi rating comes from. You will only find this at plumbing supply houses. PEX-B is what you'll find at the hardware store and is lower quality. It will probably have slightly lower ratings (and be less flexible).

All this being said, your overflow won't be carrying any pressure so I think it would work just fine, even carrying 210F water from T&P. But why do it? First, not to code. Second, you have a working, existing setup. If you're concerned about the looks, why not hit the copper with a wire brush & some steel wool. It will gleam like the day it was installed.

 

[Jadnashua]

Assuming you're planning to use 1/2" pex, I think you'll find that the code says there can be no restrictions in the piping...the ID of pex creates a restriction. It's just not a good idea.