The water heater in my house is in the middle of the structure, first floor. The over pressure valve is routed to a crawlspace under the house, not outside of the structure. I want to install a new water heater and put a drain-pan at the same time.

My plan was to run 2 drain lines, one from the drain pan, the other from the overpressure down into the crawlspace and then to an outside wall to prevent my crawlspace from being flooded if there was ever an issue. They would be routed out of the structure by cutting holes in a vent (not cutting holes in the concrete).

The total run is about 100ft (50ft x 2 lines) from the middle of the house to the outside wall, can I use pvc for these drain lines or is there other alternative to copper? I'm not sure if it matters but it does get cold in the crawlspace, not quite down to freezing but it can get close. All of the other pipes in the crawlspace are copper.

I don't think it's allowed. Don't have a copy of the UPC to check. But, you cannot use PVC. CPVC is OK.

This explains what I know:
Water Heater Pressure Relief Valve

I'm not sure what type of water heater you have, however, I might be more inclined to use the drain pan and use something like the Water cop to stop the low of water into the inlet of the heater.

Water Heater Pressure Relief Valve

You could still drain the pan to the outside.

There are some other safety systems available that can dal with the gas valve, etc.

No PVC. PVC cannot carry hot water. Use type M copper. However, you can use PVC if it is used for pan run off only.

In your situation, we are allowed to do one of the three things:

1. Run 3/4" copper T&P valve run off to the pan. Terminate this pipe about 2" above the bottom of the pan - but under the rim of the pan. Then, run 1" copper pipe from the pan to the outside. ( if T&P valve leaks, it will drip into the pan / pan will fill up and drain through pan run off line )

2. Combine 3/4" copper T&P valve run off pipe with 1" pan run off line. Run to the outside.

3. Run 3/4" T&P valve pipe to the outside. Run 1" pan run off to the outside

In Option 1 and 2 you will run only one run off pipe. But it has to be copper. This pipe has to terminate 6" above the ground.

In Option #3 you will run 1" PVC and one 3/4" type M copper - both to the outside. In this case, PVC can terminate above your window in the eve - but copper has to terminate 6" above the ground.

Hope that helps...

Thanks guys -- good to know that PVC is a no-go. I like options 1 or 2, it's less copper than I thought I had to buy, by half, so right there is a decent savings over what I'd planned to do. Also good to know about the 6" above ground termination also, I'd planned to terminate a little closer but can easily make that adjustment. Thanks again...

Milo,

We aren't even allowed to use CPVC. But we are able to use those $3 metal headed plastic blow off pipes. The difference is that the plastic unit (which looks like sch 10 PVC) is rated for up to 105,000 BTU, the rating of the T&P valve, and it is listed. The CPVC one we make up is not listed for that application. Go figure. Type M copper is acceptable for one fabricated on site. We are allowed to use 1" PVC for the pan drain line though.

Quote:

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can I use pvc to for the overflow valve of a water heater

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No! PVC isn't rated for hot water.
We pipe our T&P valoves with Type "L" ridged copper. Cheers, Tom