T&P Relief Valve Question

Discussion in 'Water Heater Forum, Tanks' started by kullboys, Dec 5, 2018.

  1. kullboys

    kullboys New Member

    Dec 5, 2018
    I am going to sleeve a stem wall so the T&P Relief Valve will exit a crawlspace and empty to the outside (6" above grade). I am trying to do the height calculations so that the Top Mount T&P valve will allow the 3/4" copper to pass through the sleeve. Can the T&P Valve be lengthened if I get one with an 8" thermostat probe?

    I just want to make sure I hit the height I need. The tank is a Low Boy Electric.

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    I don't think you are allowed to have the outlet rise above the height of the valve. If it did, it's possible there would be water trapped inside of the drain portion, that could freeze, blocking the outlet which, in a worst case situation the T&P valve is supposed to stop, allow it to build pressure and explode. It can go horizontal from the outlet if there's slope so it drains, but some inspectors and instruction manuals may not allow that. the instruction manual trumps codes, generally. If there are none, the code prevails.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    sorry, but since the instruction manual is "universal" and the code applies to the local area, IT takes precedence, unless the instruction manual has a "higher" level of safety, which is not likely.
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