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Thread: Routing pressure relief valve line

  1. #1

    Default Routing pressure relief valve line

    I am wondering about the best method to route the drain line attached to the temp&press relief valve in my water heater. My current heater is in the middle of the house, in a laundry closet that has no floor drain. house is on a slab. Current water heater has a 3/4 copper tube soldered to the valve and running down the side of the heater. With this setup, if the valve blows, water all over the wood floor and I am screwed.

    I am considering the feasibility of running the the relief tubing into the PVC washer drain in the closet. My concern is, will the PVC drain pipe withstand the high temp of the water that would be discharged from the relief valve if it tripped? I didn't think PVC drain pipe would stand that high of temp (210 F ?) I really don't have any other solution. Any other ideas??

    thanks !!!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    This is what I think I'd do (it'd be much easier done while installing the tank, though):

    I'd install the tank in a pan. You'd need to basically plug the outlet so it can hold some water. I'd also install a WAGS valve www.wagsvalve.com. The valve will shut the water off if it detects 1/2" of standing water. If it is a gas WH, it can also be set to disable the gas valve. If installed by a certified installer, comes with a big warranty against leak damage. Made by a well-known manufacturer.

    I think I saw a pseudo pan that you can install afterwards that glues to the floor to contain the water instead of setting the WH into it. Probably doesn't work as well, but might work for you if you're not willing to do the work to insert a pan underneath.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    I have seen a lot of water heaters with TP discharged to laundry standpipe. I don't know if they accept that anymore, as it would still pose a potential safety hazard if you were near it. The PVC would not melt at that temp.

    Around here, the common method for your setup is to put a Watts 210 temperature activated gas shut off in the TP hole on the tank. Then you have to put a 3/4" 150 PSI pressure relief valve on the main water supply, on the house side of any PRV or shutoff valve.

  4. #4
    Master Plumber master plumber mark's Avatar
    Join Date
    Feb 2005
    indianapolis indiana - land of the free, home of the brave....
    Blog Entries

    Talking do as jimbo says

    when you have no other recourse ,

    pipeing the t+p valve to the washing machine box

    is acceptable in my book.... I do it all the time

  5. #5

    Default DUX airoheat

    how do DUX airoheat hot water units work?

  6. #6
    DIY Junior Member hidden 1's Avatar
    Join Date
    Mar 2009


    Hi ,i didnt have a drain in floor either and had the choice of a adjustable pressure relief valve before the heater on cold line(temp adjusted just below the one on water heater)- then emptied out in washer drain.Or to run off that existing prv to the same drain.sealed entrance.no mess!


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