Standing water in the bottom of the dishwasher after a completed cycle is one of our most frequent calls, and the good news is that the drain pump itself is usually the last thing at problem, not the first.
Start with the filter
Most modern dishwashers have a removable filter assembly at the bottom of the tub that has to be cleaned by hand – it is not self-cleaning, whatever the manual’s illustration seems to imply. Food debris, glass fragments and the occasional produce sticker collect there and restrict drainage well before anything mechanical fails. This alone accounts for a large share of the “not draining” calls we run.
Check the air gap or high loop
Where a dishwasher drains under a sink, either an air gap fitting (the small cylinder often visible on the countertop) or a high loop in the drain hose prevents sink water from siphoning back into the dishwasher. If the air gap is clogged, or the high loop has sagged, water will not drain properly even with a perfectly healthy pump.
The garbage disposal connection
If your dishwasher drains through the garbage disposal, a disposal that has never been run – common after installing a new dishwasher – can have a knockout plug still in place, blocking the drain path entirely. A disposal that is simply clogged has the same effect.
When it actually is the pump
If the filter is clean, the air gap and hose are clear, and the disposal runs freely, the drain pump or its check valve is the more likely cause, and that is a component-level repair. We test it directly rather than replacing it on a guess, since a pump that tests fine but has a stuck check valve looks identical from the outside.
A habit that prevents most of this
Scraping plates rather than rinsing them heavily reduces filter clogging significantly – modern dishwashers are designed to handle food residue, but not bones, produce stickers, or large scraps.
