Symptoms
- Sink fills with dirty water during the washer's drain step
- Gurgling sound from the sink drain
- Slow drainage in the sink even without the washer running
- Problem happens consistently during every spin or drain cycle
Likely causes
- CommonClogged shared drain line or standpipeIf the washer drains into a standpipe connected to household plumbing, a clog downstream forces water back up the path of least resistance.
- PossibleImproperly sized or installed standpipeA standpipe that's too short, too long, or the wrong diameter can cause drainage problems.
- PossibleBlocked or vented drain venting issueImproper venting in the plumbing can cause air pressure issues leading to backup.
- PossibleGeneral household drain clog unrelated to the washerA clog further down the line affecting multiple fixtures can show up first at the washer connection.
What to do
- Check if the sink drains slowly even when the washer isn't running, which points to a general household clog.
- Try a natural drain cleaner or a plumbing snake in the sink drain if it's a simple sink-side clog.
- Check the standpipe height and make sure the washer's drain hose isn't inserted too far down, which can cause siphoning issues.
- Avoid pouring grease or food waste down the connected sink if it's a kitchen sink sharing the line.
- If a simple snake doesn't clear it, avoid repeated chemical drain cleaner use, which can damage older pipes.
- Call a plumber if backup continues, since this usually indicates a clog or venting issue in the shared drain line.
Tools and parts
- Plumbing snake
When to call a pro
If a simple snake doesn't clear the backup, a plumber should check the shared drain line and venting.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.