Proper drain for water heater?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by davidgrove, Oct 17, 2007.

  1. davidgrove

    davidgrove DIY Junior Member

    Oct 22, 2005
    As part of a remodel, I want to put a 50 gal. electric water heater in an existing utility room. The existing floor is vinyl over 1 1/4" plywood subfloor. There is no drain in the floor. I do have access to the floor from underneath. I need a drain for the temperature/pressure relief valve (overflow) pipe.

    The question is how to install a drain. I'm not putting in a shower or tub, I just want a small drain, flush with the floor, so I can bring the overflow pipe down to (6" above) it.

    I saw a drain at Home Depot that I think might work. It is some kind of plastic-like material (intended for lawn I think). It has screen (top) that could be flush with the floor, and a sort of a "stepped" or wedding cake like shape underneath. I'd cut a circle through the vinyl and scrape it off, then at a smaller (maybe 3/8" less) diameter, cut all the way through the floor. The drain could rest on the wooden lip and be flush with the floor. Then connect up to DWV line. The drain would be along a wall, behind a cabinet, and not readily accessible to any foot traffic.

    Could this work? Is there a better or proper way to do it?

    Thank you for any suggestions.


    David Grove
  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    Without a trap primer that drain will vent sewer gas as soon as it dries out from lack of use.
  3. Sponsor

    Sponsor Paid Advertisement

  4. davidgrove

    davidgrove DIY Junior Member

    Oct 22, 2005
    Thank you for the tip.

    What does one normally do for a drain in a location that is never or very infrequently used? How are water heater drains typically handled?


  5. davidgrove

    davidgrove DIY Junior Member

    Oct 22, 2005
    The real question...

    Do I really need to install a drain?

    I went to a local hardware store to get some stuff to connect up the plumbing, and I chatted with one of the owners. He was surprised at my wanting to install a drain. He said that in 60 years, he hasn't known anyone who put in a drain to install a water heater, and that he's never had a customer ask about it. He suggested just letting the overflow pipe go down the side of the water heater and (potentilly) drain into the tray (under the water heater).

    Thank you.

  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    There are two things that typically leak on a WH: when a seam fails, and if there is a fault and the T&P valve discharges. Under normal conditions, neither should leak. Installation of a pan will help contain a small amount of water. If it leaks and nobody is there to notice, it can create a huge amount of damage when it is in the living space. Running that overflow to a proper drain is like buying an insurance policy - you hope you never need it, but are really glad if it is. Lots of WH are installed without a drain nearby, but many of them are in the garage or basement where a leak is annoying, but may not create a lot of damage. Check with the local inspector to see if you could run a drain line from the pan directly outside without running it into the sewer.
  7. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    T&P Valves usually have a pressure relief setting of 150 pounds and 200 to 210F on temperature.

    In a situation like yours, I would put the discharge from the T&P valve to the pan. That would satisfy the code requirement.

    Then, I would add a small 75 or 100 psi, 1/2", pressure relief valve on the cold water line supplying the water heater, located in some safe area that has a drain.

    That relief valve will prevent the pressure in the hot water heater from ever exceeding the pressure setting on the T&P valve. The risk that the temperature will ever cause the T&P valve to release is very small.

    Those small relief valves are usually sold as relief vavles for submersible pumps and typically cost $10 to $20.
  8. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    pan and a drain

    If you can install a metal drain pan...$17 bucks....

    this is a good idea to do either way...

    they usually have a 3/4 or 1 1/2 drai on the side of them....

    just put the pop off valve into that pan and run a sch
    40 pvc drain off that pan either to the nearest drain or to the
    nearest path down in to the crawl space...

    we do this all the time and it seems
    to keep small or large floods from happenning..

    that is what they are made for

    and dropping the drian pan into the crawl space never hurt
    anyone, usually the pop off valve will blow into the pan and
    eventually you will notice this going on
    Last edited: Oct 21, 2007
  9. davidgrove

    davidgrove DIY Junior Member

    Oct 22, 2005
    Thank you

    Thank you all, for your friendly and very helpful advice.

    I already have the pan installed. There is no existing drain conveniently located, so will add the pressure relief valve on the cold side.


Similar Threads: Proper drain
Forum Title Date
Plumbing Forum, Professional & DIY Advice Proper Fitting for Tub Drain/Vent Sep 9, 2017
Plumbing Forum, Professional & DIY Advice Proper method for piping existing floor drains Apr 4, 2017
Plumbing Forum, Professional & DIY Advice how to properly do drain for the washer Mar 23, 2017
Plumbing Forum, Professional & DIY Advice Proper venting of washing machine and sink drain in basement Mar 13, 2017
Plumbing Forum, Professional & DIY Advice Proper drain slope on short run Feb 7, 2017

Share This Page