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  1. #1
    Join Date
    Feb 2009
    Posts
    2

    Default Washing machine drain routing

    Hello - I'm planning to install a washer/dryer in a first-floor walk-in closet. I'm wondering if it is OK to run the washer outlet through the floor to the basement and into a trap down there as opposed to the typical 4-foot standpipe style drain hookup. Are there any issues with this approach? Thanks for the reply - Bob Muller Upstate NY

  2. #2
    Join Date
    Jan 2009
    Location
    Needham, MA
    Posts
    559

    Default Re: Washing machine drain routing

    if the distance between where the water enters the pipe and the trap is too great, the force of the water coming down can push the water right out of the trap and therefore eliminate your buffer between your house and sewer gases. there is an allowable distance that i'm talking about, i just don't know what it is. doesn't sound like the best plan to me, maybe a plumber will respond to give you some additional advice.

  3. #3
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,607

    Default Re: Washing machine drain routing

    The washer drain needs to have some kind of siphon break that's at a level above the water level in the washer. In most houses, this is accomplished by the standpipe: the washer drain hose loops above the high water level and the large diameter of the standpipe (larger than the hose) provides an air gap to prevent siphoning.

    If the loop of the hose is below the high water level, water can be siphoned out of the washer. If you just run the hose straight down through the floor, your washer will never fill.

    What you may be able to do -- and this should work, if acceptable to your local code inspector -- is to extend the standpipe above the floor but have the trap below. Be careful that you don't have the trap in an area where it could freeze. That could cause an unexpected flood in your laundry room!
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  4. #4
    Join Date
    Feb 2009
    Posts
    2

    Default Re: Washing machine drain routing

    Thanks very much guys - I guess I'll go with the sub-floor trap as the basement never goes below 45 deg. F or so.

    I figured there was some reason it was never done this way!

    B

  5. #5
    Join Date
    Dec 2008
    Location
    Midwest
    Posts
    173

    Default Re: Washing machine drain routing

    The stand pipe length out of the top of the p-trap is no shorter than 18" and no longer thatn 30" The pump on the washer should prevent any siphonage out of washing machine tub

  6. #6
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,607

    Default Re: Washing machine drain routing

    Quote Originally Posted by MSSP View Post
    The stand pipe length out of the top of the p-trap is no shorter than 18" and no longer thatn 30" The pump on the washer should prevent any siphonage out of washing machine tub
    Not necessarily. I accidentally pulled the drain hose off my washer once when it was full of water and it made a big mess!
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

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