Quick Answer:
Clean the dishwasher filter, then press the drain/cancel cycle and listen. If the dishwasher drains with a strong, continuous sound and water leaves the machine, the immediate backup is likely cleared. If the sink still fills or the drain sounds weak, stop using the machine and check the drain path or call a professional.
Why This Happens
When the dishwasher filter is clogged with food, grease, or bits of debris, water can’t flow freely from the sump into the drain line. The filter sits between the tub and the pump; if it’s blocked the pump struggles to move water and water can back up into the sink. Other common contributors are a misrouted drain hose, a blocked air gap, or a partial clog in the sink or garbage disposal. A misrouted or kinked hose is a frequent cause — sometimes described as Dishwasher drain hose installed wrong.
Step-by-Step What to Do
1. Stop the cycle and remove standing water
- Cancel the cycle and open the door. Wait for the water level to drop if the machine finishes pumping.
- Scoop any excess standing water into a container and dispose of it in the sink (with the sink drain clear), or carefully mop it up.
2. Clean the filter
- Pull out the bottom rack to access the filter area. Most filters twist out or lift out—check your manual if unsure.
- Rinse the filter under warm running water and remove trapped debris with a soft brush or cloth. Avoid forcing tools into the filter housing.
3. Run the drain/cancel and listen closely
- Replace the filter and bottom rack. Start the machine on the drain or cancel drain function.
- Note whether the drain-out sounds strong and continuous. A strong, steady pumping noise usually means the pump and hose are moving water; a weak, intermittent or labored sound suggests a partial blockage or pump problem.
4. Check the sink, disposal, and air gap
- If your dishwasher drains into a garbage disposal, run the disposal briefly to clear any obstruction (with the power off to the dishwasher as a precaution).
- Inspect and clear the sink drain and air gap if present. A blocked sink drain will cause dishwasher water to back up into the sink.
5. Inspect the drain hose routing
- Look under the sink to confirm the drain hose is not kinked or trapped. A high loop or air gap should be present where required.
- If the hose appears misrouted or crushed, reposition it so it flows upward to a high loop before dropping to the drain.
6. Test a full short cycle
- Run a short rinse or light wash to test. Watch and listen at the sink during drain-out to confirm the water goes down smoothly and the sound remains strong and continuous.
- If backups return or the pump sounds strained, stop using the appliance and move to the next step.
What Not to Do
- Do not keep running the dishwasher with a clogged filter; it can worsen backups and strain the pump.
- Don’t stick your hand into the sump while the machine is running. Turn the power off before reaching inside.
- Avoid pouring chemical drain cleaners into the dishwasher drain or disposal; they can damage components and are not effective for dishwasher sump clogs.
When to Call a Professional
Call a licensed appliance technician or plumber if any of the following are true:
- The drain sounds weak or the pump runs but water does not move after you clean the filter and clear obvious blockages.
- Water continues to back up into the sink or the sink still fills during dishwasher drain cycles — this suggests a deeper drain line obstruction or disposal issue, or a problem that needs more than basic troubleshooting such as when the sink fills while the dishwasher runs (Sink fills when dishwasher runs).
- You see leaks from hoses, fittings, or the pump area, or smell burning or hear grinding noises from the motor.
Safety Notes
- Before reaching into the dishwasher for anything beyond the removable filter, cancel the cycle and turn off power to the appliance at the switch or breaker if possible.
- Hot water and steam can cause burns—allow the appliance to cool if it has been running recently.
- If you must work under the sink, place towels to catch spills and use a bucket to collect drained water. If you’re unsure, stop and call a professional.
Common Homeowner Questions
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Q: Will cleaning the filter always fix the backup?
A: No. It often fixes minor backups, but if the drain hose, garbage disposal, or the drain line is blocked, the problem may persist. -
Q: Can I use a plunger on the sink to help?
A: You can try a sink plunger on the sink drain, but avoid plunging the dishwasher itself. Plunging may help a sink-side clog. -
Q: How quickly should I call a pro?
A: Call a professional if cleaning the filter and clearing obvious blockages don’t restore a strong drain sound or if backups continue.