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bobtabla
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

MLBSF
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.

Fencepost
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!

bobtabla
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

MSSP
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

Fencepost
Re: Washing machine drain routing
MSSP wrote:

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!

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