water line issues between shower and hot water tank drain P-trap

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ns, Feb 28, 2011.

  1. ns

    ns New Member

    Messages:
    2
    Location:
    Vancouver, BC
    I have a hot water tank in a 'closet' next to the bathroom (all on the second floor). I had a leak fixed from the hot water tank drain pan where it attaches into the floor drain (water was leaking through to the ceiling on the first floor). There are two pipes discharging into the tank's floor pan drain: the tank's overflow pipe and a small copper water supply line coming from the wall. The plumber told me that little copper line is supposed to drip a little water into the floor drain/p-trap, but the problem is it gushes water whenever I turn the shower lever on. It doesn't happen when just the tub water is running.

    The plumber securing the little copper line so its pulled further down into the drain to prevent the water from splashing upwards into the drain pan. Will all that pressure of the water eventually cause leaking of the plastic/pvc(?) pipes down the line? Should I get the problem investigated and fixed (which would require opening up a few different walls including my bathtub surround) or can I leave it be?
    Last edited: Mar 1, 2011
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,401
    Location:
    Yakima WA
    What it sounds like to me is you have what we call a "closed" system and your Temperature/Pressure valve on the water heater is tripping due to water expansion created when the water heat is activated. A closed system is created when there is a check valve in the water supply line that prevents the expanded water from being absorbed by the water main. The check frequently is a Pressure Regulator Valve, but can be in the water meter itself. When water heats, it expands and if this expansion is not dealt with, the pressure in the water heat will rise rapidly and trip the T/P valve which is a safety device to prevent the heater from exploding. When the heating stops, the pressure returns to normal and the T/P closes. The cure for the problem is to install a thermal expansion tank in the cold water supply line between the PRV and water heater. This is an air-charged tank usually about 2 gallon size and this provides a place for the expanded water to reside until the pressure lowers. I think what you refer to a "the little copper line" is the pipe from the T/P valve. It does not, or at least is absolutely should not, connect solidly to the drain, so it does not pressurize the drain, and it should it never drip a water. By the way you describe your problem, it appears you are unfamiliar with plumbing basics, so I would urge you to hire a professional plumber to deal with this problem. It should not require opening walls, and if my diagnosis is correct, installing an expansion tank is quite simple. (It does have to be done correctly however)
  3. ns

    ns New Member

    Messages:
    2
    Location:
    Vancouver, BC
    Thanks for the reply! I've edited my post to hopefully be a little clearer.

    The plumber was already in and was the one who told me I'd end up having to open up walls to figure out the source of the problem. He'd already installed an expansion tank when trying to troubleshoot the source of the leak. I have both the tank's overflow pipe and that little copper water supply line discharging (not solidly fixed) into the drain pan floor drain.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,304
    Location:
    Cave Creek, Arizona
    The little pipe is from a "trap primer". It is a device to maintain the trap seal in the floor drain since you would not normally run any water into it. It IS designed to discharge water when a faucet is used. There are different models, some dribble a few drops of water when any faucet is used, some do it when a specific faucet is turned on, but still others, and yours may be one of those run a stream as long as the faucet is turned on. Whether there is even anything wrong with it is not apparent without knowing which kind you have. Normally, they are only defective when they run water continually. But, having said that, whoever piped the heater's safety valve into that pan did NOT do you any favors, because if it EVER operates the pan may overflow in a matter of seconds and flood the area.
  5. Jerome2877

    Jerome2877 In the Trades

    Messages:
    397
    Location:
    BC
    Pulling the pipe into the drain is not allowed as you are creating a cross contamination between the water supply and the sewer.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,360
    Location:
    New England
    You could put a valve on that line and 'throttle' it back a bit, especially if the shower gets used frequently. A trap doesn't lose much water, and if you use the shower daily, a bit each time is all that is needed to keep the trap full. If a trap dries out, it provides an open connection to the sewer and you can get sewer gasses, files, etc. into the space. Keeping it full of water prevents that for the most part, so, that's why it has a trap primer there.
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