Home>Discussions>PLUMBING>Washing machine drain overflows
6 posts / 0 new
Last post
Washing machine drain overflows

When our washing machine drains out into the washer box/drain, the water backs up. We know the drain is not clogged as we can run a hose of water through it for some time with no problem. The house has been remodeled, so we do not know if this is new plumbing or original plumbing. It is all sheetrocked in and the drain pipe is hidden or enclosed in a wall box. We can't get under the house to see anything either. We don't know what else to try. The house was built in '66, so maybe there's an old plumbing issue. Any advice?

Re: Washing machine drain overflows

In 1966 chances are that the line is 1½" and most newer washing machines require at least 2". One poster on here said they solved the problem by changing the stand pipe to 4" and left the rest of the line at 1½". I don't recommend that but feel obliged to pass the info on.


Re: Washing machine drain overflows

Can't say I agree with Jack on the requirement of a 2 inch line.
As far as I know many plumbing codes still require a minimum 1-1/2 inch drain for washing machines and have yet to see a 2 inch specified requirement by a washer manufacturer.

Consider the millions of residences that have a washing machine discharge into a 1-1/2 inch line without issues.

In my own home of over 55 years the drain system ... for the most part ... is original.
Back in the day there was no drain pipe setup for a washingmachine ... typically the floor drain ... in this case .... was used for the discharge from the washer.
When I see older homes ( depending on how old ) with a drain pipe for a washer it indicates to me that it was added ... and raises the question .... was it done properly?

Things like .... is the drain less than 1 1/2 inches inside diameter .... does it have the proper slope .... is it vented .... or too far from a vent .... improper connections with 90's or tee's for the drain ....partial blockage ….. are examples that may create issues.

Running water from a garden hose really only indicates the drain isn’t totally blocked and doesn’t verify proper venting

Any shortcomings in the drain will show up when something like a washer.... new or old .... that discharges a fair volume of water from a pump with a larger diameter hose.

2 cents worth.

Re: Washing machine drain overflows

I would say you have a partial stoppage. The line needs to be snaked.


Re: Washing machine drain overflows

Agree with John, try a 25ft. snake. I had this problem as well and snaking did the trick. It either pushed it through or cleaned it enough to drain ok. One other thing...has your washing machine been repaired recently? I ask because it may have a more *****ful pump. You may want to ask a washing machine expert to see if they have any suggestions if the snaking doesn't work. Good luck!

Re: Washing machine drain overflows

Per code washing machine stand pipes are to be 2" and no less than 18" and no more than 30" above trap. Could be your p-trap is an older cast iron You should be able to look inside your washer box and see what kind and size pipe is. I have seen alot of stand pipes 1 1/2" but as they strat to corrode and deposit inside they clog up quick with the newer type washers . They dump about 4-5 gallons in a very short time.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.