washer drain fills sink

My washing machine drain is connected to the same drain pipe as a utility sink. Each time the washer drains, it drains into the sink,then the sink drains. Is this any cause for concern?

Newer washers dump their water very quickly. Code today requires a 2" drain for that reason. It could be your drain is only 1-1/2", it could be partly clogged, or it could be both too small and partly clogged. If this is something that has just begun to happen, my money would be on one or both of these problems. It isn't going to get better on its own, so you might want to have a plumber in to auger the drain.

1) If it drains directly into the sink (with a pipe looped over the sink and water sploshing from this into the sink), even if you have a 1.5" pipe then it is code compliant and it is not necessarily a problem as long as the drainpipe is not blocked. My washer drains this way and the sink fills about half full but it all goes away and never overflows.

2) If it drains into a standpipe that is connected to the pipe that drains the sink then it really does need to be 2" and you may or may not have a problem depending on whether the standpipe is properly vented (it should be) and/or there is a blockage that is causing water to backup into the sink.

Which do you have? 1) is probably easier to fix than 2).

It drains into a 2" standpipe that is connected to the pipe that drains the sink.

Then I suspect the drain is partly clogged unless the 2" standpipe was reduced to 1-1/2" which would be totally against code, but if a handyman did the washer standpipe, he might have done just tapped into the existing drain which could be 1-1/2". That's probably not too likely, just an outside possibility. Get a plumber to auger the drain clear out to the street and you should be good to go.

Would a house built in the early 60s be likely to have a 1 1/2" drain pipe for washing machines? Would that explain why a new washing machine wouldn't drain properly?

Thanks,
John

It is very possible. Washing machine the those days didn't expel their water nearly as fast. If the drain line is galvanized steel, it could be corroded as well. If it was mine, I'd explore starting with the standpipe. If it is 2", it is unlikely they would have reduced it as that is a really big no no in plumbing. If the stand pipe is 1-1/2", then you would need to see if it goes into a large pipe and where. If you are lucky, it would just be a small stand pipe and would be fairly easy to change to 2" without major plumbing changes.

Thanks Gary,

The stand pipe is 1 1/5" and goes into the wall so I can't see the size of the final pipe. The drain pipe from the wall for the sink is 2". Do you think it's safe to assume that behind the wall there is a 2" pipe that the stand pipe connects too?

Thanks,
John

Thank you Gary and others for your replies. To answer your questions, the house was built sometime in the fifties. My Whirlpool washer is over ten years old. The standpipe is two-inch black plastic. Out of curiosity, I turned off a shutoff valve on the standpipe (located below the utility sink and above the washer connection) to prevent the washer water from backing up into the sink. The washer drain water leaked through a caulked joint (between the washer and the standpipe) onto the floor. So what is the purpose of the valve? Next I will try a strong drain cleaner, then an augur.