Symptoms
- Sink water rises specifically during the dishwasher's drain cycle
- Sink drains normally at other times
- Gurgling noise coincides with the dishwasher pumping out
- Problem is consistent every wash cycle
Likely causes
- CommonClogged disposal chamber restricting the shared pathDebris sitting in the disposal narrows the passage the dishwasher water must travel through.
- CommonMissing air gap or a clogged oneAir gaps prevent backflow but need to be clear to work properly.
- PossibleHigh loop in the dishwasher drain hose missing or dislodgedWithout a high loop or air gap, dirty water can siphon back.
- PossiblePartial clog in the branch drain line downstreamA narrowing further down only shows symptoms under the higher flow of a pump-out.
What to do
- Run the disposal with water to flush out anything sitting in the chamber before running the dishwasher again.
- Locate and clean out the air gap on the counter near the faucet if your setup has one.
- Check under the sink that the dishwasher drain hose has a high loop secured up near the countertop if there's no air gap.
- Run the dishwasher's drain cycle and watch the sink and air gap closely.
- If backup continues, remove the trap under the sink and check for a clog in the branch line.
- Note whether backup happens on every cycle or only heavy loads, which can help a plumber pinpoint a partial clog.
Tools and parts
- Flashlight
- Bucket
- Adjustable pliers
When to call a pro
If flushing the disposal and checking the air gap don't resolve it, a plumber should check the branch drain line for a partial clog.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.