Dishwasher Not Draining: Clear the Filter, Hose and Air Gap

Opening a dishwasher to find a pool of dirty water is unpleasant, but it is one of the easiest appliance problems to diagnose. A dishwasher drains by pumping water out through a hose, usually into the garbage disposal or the sink drain. Water that stays behind is being stopped somewhere along that path, and you can check most of it without tools.

How a dishwasher drains

At the end of each wash and rinse, a drain pump at the bottom of the machine pushes water through a filter and out a flexible drain hose. The hose runs up under the counter, often through an air gap on the sink deck or in a high loop under the sink, then connects to the garbage disposal inlet or a fitting on the sink drain. The high loop or air gap prevents dirty sink water from siphoning back into the dishwasher.

Diagnose the drain problem

What you notice	Likely cause
A little water in the sump only	Normal on many models; a small amount stays to keep seals wet
Several inches of water, food bits on top	Clogged filter
Problem started right after a new disposal was installed	Knockout plug still in the disposal’s dishwasher inlet
Water backs up out of the sink air gap	Clogged air gap or hose
Sink drains slowly too	Clog in the sink drain or disposal
Dishwasher hums at the end of the cycle but water does not move	Drain pump blocked or failed
Error code on the display	Check the manual; many models report drain faults

Step 1: Clean the filter

1. Turn the dishwasher off and remove the lower rack.
2. Soak up standing water with towels or a cup.
3. Find the filter at the bottom of the tub, usually a cylinder you twist and lift out, with a flat mesh screen beneath it.
4. Rinse both under running water and scrub with a soft brush. Do not use wire brushes on fine mesh.
5. Clear any food, glass or seeds from the sump below.
6. Reinstall the filter and lock it in place.

Many owner’s manuals recommend cleaning the filter regularly. ENERGY STAR advises scraping food off dishes rather than rinsing them, which saves water and energy; scraping large scraps into the trash also keeps the filter from loading up.

Step 2: Check the disposal connection

If the dishwasher drains into a garbage disposal, run the disposal briefly with water to clear it. On a newly installed disposal, the dishwasher inlet has a plastic knockout plug that must be removed; if it was left in place, the dishwasher cannot drain at all. With the power off, look inside the inlet where the hose connects. A plug can be knocked out with a screwdriver and hammer from inside the inlet, then fished out of the disposal.

Step 3: Clean the air gap and check the hose

The air gap is the small chrome or plastic cap beside the faucet. Pull or twist off its cover and remove any debris inside. Under the sink, follow the drain hose and look for kinks or a section crushed behind the dishwasher or under storage. If there is no air gap, the hose should rise in a high loop fastened under the countertop before going down to the drain.

Step 4: Check the drain pump

With the power off at the breaker, remove the filter and look at the pump opening in the sump. Bits of glass, fruit pits or labels can jam the impeller. Remove anything you can reach carefully. Some models allow you to turn the impeller by hand. If the pump hums but does not move water after it is clear, it has likely failed and needs replacing according to your model’s service instructions.

Prevent drain problems

• Scrape plates into the trash before loading, as ENERGY STAR suggests.
• Clean the filter on the schedule in your manual.
• Run the disposal before starting the dishwasher.
• Keep grease out of sinks and dishwashers; the EPA notes that grease and food solids also burden septic systems.

Common mistakes

• Using drain cleaner in the dishwasher. It can damage seals and plastic parts.
• Forgetting the knockout plug after a disposal install.
• Leaving the filter loose after cleaning, which lets debris reach the pump.
• Working near the pump with power on.

When to call a technician

Call an appliance technician if the drain pump hums but will not run after clearing, if the machine shows a drain fault after the filter and hose are clear, if water leaks from under the dishwasher onto the floor, or if you need to remove the dishwasher from the cabinet to reach the hose. Leaks under the machine can damage flooring and cabinets quickly.