Dishwasher Not Draining: What to Check First
Dishwasher won't drain? Check the filter first, then the drain hose, air gap and disposal knockout — and know when the pump needs a technician.
A dishwasher that won’t drain is often a blockage or a drain-connection problem before it’s a failed pump. Work the owner-accessible checks below in order — cheapest and least invasive first. Then decide whether it’s a technician job.
Before you start: switch off and unplug the dishwasher (or switch off its breaker). Don’t open a pump housing or test electrical components on a live machine. Component tests and pump replacement are technician work — if the checks below don’t resolve it, have it diagnosed against your model.
1. Clean the filter (check this first)
Most dishwashers trap food debris in a filter assembly at the bottom of the tub. When it fills up, water can’t get out.
Check: pull the bottom rack and remove the filter — a twist-and-lift cylinder or a flat mesh panel depending on the model, per your manual. Rinse it under the tap and scrape off anything caked on. Also check the sump area underneath for broken glass, pits, or labels that slipped off jars. Refit the filter and run a rinse cycle to confirm.
2. Check the drain hose (kinks, clogs, sag)
The drain hose runs from the dishwasher to the sink drain or garbage disposal.
Check: with the machine off and a towel down, look for kinks, pinch points, or a low spot where water pools. Follow your model’s manual for how to access the hose (dishwashers sit on adjustable feet and are typically held by a couple of screws at the cabinet). If the hose is gunked beyond cleaning, replace it — a drain hose is matched to the machine, so confirm your model before buying.
3. Air gap and disposal knockout
If the dishwasher drains into a garbage disposal, its inlet has a knockout plug that must be removed (some installers miss it). There is also a small countertop cylinder — the air gap — that can clog with debris.
Check: look for the knockout plug at the disposal inlet (it’s documented in the disposal/dishwasher installation instructions) and clear the air gap cap of any gunk. If your sink drains slowly too, the shared drain may be blocked — run the disposal with water flowing.
4. Drain pump — technician territory
If the filter is clean and the hose, air gap and disposal are clear, the remaining possibilities are inside the machine: the drain pump or its check valve. You may hear the pump hum without water moving, or hear nothing.
This is not an owner check. Testing the pump and replacing it means opening the machine and working with electrical parts; have a technician diagnose which component is at fault for your model, then replace the confirmed part. Don’t order a pump on the symptom alone.
The order that matters
- Clean the filter — free to inspect, do it first
- Check the hose, air gap, and disposal knockout — owner-accessible
- Drain pump / check valve — get a technician’s diagnosis before replacing anything
Parts & tools you may need
- Dishwasher filter (only if yours is cracked or warped)
- Replacement drain hose (match your exact model)
- Towels and a shallow pan
No multimeter step here — pump testing and replacement are a technician job.
FAQ
Q: Why is my dishwasher not draining but the filter is clean? A: Move to the drain hose — check for kinks and flush it. Then check the disposal knockout plug and the air gap before suspecting the pump, which needs a technician’s diagnosis.
Q: Can a clogged garbage disposal cause the dishwasher not to drain? A: Yes — if the disposal or the shared drain is blocked, water backs up into the dishwasher. Run the disposal with water flowing; if that fixes it, that was it.
Q: How much does it cost to fix a dishwasher that won’t drain? A: It depends on the diagnosed fault and your model and region, and whether you hire a technician. Check current prices for your model; we don’t quote a figure without a diagnosed fault.