Quick answer
The dishwasher usually drains through the kitchen sink's drain or the garbage disposal, so when the sink gurgles or fills with dirty water as the dishwasher pumps out, the shared drain is partly blocked, most often by grease and food in the trap or the line past it. Run the disposal, check the dishwasher hose has a high loop or air gap, and clear the sink trap. If the sink still backs up, the kitchen line needs a snake. HomeServe puts drain cleaning at $100–$275. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed November 4, 2026· Next review May 2027
In most kitchens the dishwasher drains through the sink: its hose connects to the garbage disposal or to a fitting on the sink drain. So when the dishwasher pumps out and the sink gurgles, or dirty water rises in the basin, the shared drain is telling you it cannot take the flow.
Check These First
- 1Run the disposal with cold water for 30 seconds. A disposal chamber full of food blocks the dishwasher's water.
- 2Check the high loop or air gap. Under the sink, the dishwasher drain hose should rise up and be fastened under the counter before it drops to the disposal. Some areas require an air gap, a small cap on the sink deck. Without either, dirty water can flow back into the dishwasher.
- 3New disposal? The dishwasher inlet on a new disposal has a knockout plug that must be removed. A dishwasher that will not drain after a disposal install is usually this.
- 4Clean the sink trap. Put a bucket under it, remove it, and clear the grease and food.
If It Still Backs Up
| What you notice | Likely cause |
|---|---|
| Both sink basins fill when the dishwasher drains | Clog in the line past the trap |
| Gurgles only, drains fine | Partial clog or a blocked vent; see drain gurgling |
| Dirty water stays in the dishwasher | Clogged dishwasher hose or air gap |
| Other drains slow too | Main line; see main sewer line clog |
Grease is the usual culprit in kitchen lines. It cools and coats the pipe, narrowing it a little more every week. Do not pour grease down the sink, even with hot water.
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
What It Costs
HomeServe puts drain cleaning at $100–$275. See kitchen sink not draining and drain cleaning.
The Call
Call when the sink still backs up after the trap and disposal are clear, or other drains are slow too. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
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Frequently Asked Questions
Why does my kitchen sink gurgle when the dishwasher drains?
The two share a drain, and a partial clog in the trap or the line past it makes the dishwasher's water push air back through the sink.
Why does dishwasher water come up in my sink?
The shared drain is partly blocked, or the dishwasher hose has no high loop or air gap, so water backs up the easiest way.
What is a dishwasher high loop?
The drain hose is looped up and fastened under the counter, higher than the sink drain connection, so dirty water cannot flow back into the dishwasher.
Sources
Methodology: How we source and verify data · Report an error
Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.
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