Dishwasher Not Draining? Work Through These Checks in Order

First, know what normal looks like

A small amount of water sitting in the recessed sump below the filter is normal and intentional — it keeps the pump seal from drying out. What is not normal is water covering the tub floor, water above the filter housing, or water that has visible food debris floating in it after a completed cycle.

Before troubleshooting, cancel any running cycle, let the machine finish draining if it can, and scoop out standing water with a cup and towel. You want a dry tub to work in, and you want to see whether it refills.

Check one: the filter and filter well

This is the cause in a large share of no-drain calls and it takes two minutes. Twist out the cylindrical filter, lift the flat screen beneath, and look at what is underneath. Labels from jars, olive pits, broken glass, and a paste of grease and starch are the usual finds.

Rinse everything under hot water, scrub the mesh, and wipe out the well. Reseat the filter properly — if it is not locked in, debris bypasses it and goes straight to the pump, which turns a small problem into an expensive one.

Check two: the garbage disposal knockout plug

If the dishwasher drains into a garbage disposal and the problem started right after the disposal was replaced, this is almost certainly it. New disposals ship with a solid knockout plug in the dishwasher inlet, which must be punched out during installation. When it is missed, the dishwasher has nowhere to drain at all.

Also worth checking: a disposal full of unground food will back up into the dishwasher line. Run the disposal with cold water for thirty seconds before your next dishwasher cycle and see if the behaviour changes.

Check three: the drain hose

Pull the machine forward if you can do so safely and look at the corrugated drain hose. Two faults are common. A kink — usually created when the machine was pushed back into the cabinet — restricts flow. And a missing high loop lets dirty sink water siphon back in.

The hose should rise up and be fastened to the underside of the countertop or the top of the cabinet before dropping down to the disposal or standpipe. If it runs flat along the floor, that is a code and function problem, and re-securing it with a zip tie often fixes the complaint outright.

Grease also congeals inside the ridges of corrugated hose over years. If the hose is old and the interior is coated, flushing it is a genuine repair step rather than a formality.

Check four: the air gap

Many homes — required in some states — have a small chrome cylinder on the sink deck next to the faucet. That is the air gap, and it prevents backflow. It also clogs with the same debris that clogs everything else.

Twist off the chrome cover and lift out the plastic cap underneath. Clear any sludge with a bottle brush and flush it. A telltale sign of a blocked air gap is water bubbling up out of it onto the countertop while the dishwasher drains.

Check five: the drain pump

If all four checks pass and the machine still holds water, the drain pump is the likely culprit — either jammed by debris or electrically failed. You can sometimes hear the difference: a humming with no water movement suggests a jammed impeller, while total silence during the drain phase suggests a dead pump or control fault.

This is where the DIY path ends for most people. The pump is under the sump, reaching it means disconnecting power and water, and there is broken glass in the debris more often than you would like. Our deep-clean service includes clearing the sump and impeller, which resolves jammed pumps; a genuinely failed pump needs replacement.

Preventing the next one

Nearly every drain fault we see traces back to solids that should never have entered the pump. Scrape plates properly, keep the filter clean monthly, and never let a machine run with a loose or missing filter. Run hot water at the sink before starting a cycle so the machine begins with hot water rather than the cold slug sitting in the pipe — hotter water keeps grease liquid all the way to the drain.