If the only time the sink backs up is when the washing machine is draining there s a good chance that they both empty into a common fitting.
Washing machine draining into bathroom sink.
Pull the washing machine out and check the connection where the flexible hose goes into from the washing machine.
This install is in a basement so it would be very difficult to cut more concrete or run a separate line to the sump.
Gray water from your washing machine backing up into your sink is one such problem and for many homeowners it can be an ongoing source of annoyance.
Thanks for all the replies.
I m redoing a bathroom laundry room and have a washing machine and sink that could easily be combined into one drain and vent if it s okay.
To start with know that your sink and washing machine drain lines tend to run congruent to each other.
This problem began only after we purchased a new washing machine and i am afraid the machine just pumps.
This means they combine at some point on the way to the main sewer line.
The laundry room and bathroom with the sink are adjacent and the washing machine drains into a drain in the wall which i assume merges with the sink drain which is slightly lower.
The thing that got me thinking about this in the first place is that we are thinking of moving the washing machine to a different wall.
It sounds like it is blocked.
This is in virginia.
They may also back up when other fixtures are draining.
I have tried running a snake into both the sink drain and washer drain but this has not solved the problem.
Why does this happen.
If the sink drain isn t 2 the only options are 1 send the hose into the sink like it is or 2 run 2 drain to the dwv which would involve cutting up the floor.
In that case the first place where the air can leave is the vent but if the vent is clogged that means that the air will exit through the sink drain.
It s common for the washing machine to share a drain with a sink and if the laundry room is near the kitchen it could be the kitchen sink.
Any other option would be a lot more work.
Both drains may empty into a toilet waste line and be.
The washing machine drain 1 5 would run horizontally along wall pick up the lavatory drain still 1 5 and wye into a 2 drain with the shower which then wyes into a 3 drain with the toilet and on to a sump.
Others go into a fitting on the u bend under the sink.