Standing water in the bottom of a dishwasher makes people assume the appliance is dying. Most of the time it is not. The dishwasher drains through the kitchen sink plumbing, and the sink plumbing is usually the problem. Here is the order we check things in, because it goes from free and easy to expensive, and the free stuff solves it most of the time.
1. The filter and the sump
Most dishwashers made in the last fifteen years have a removable filter in the floor of the tub. It twists out. If it is packed with food, glass, a fruit sticker or a bit of a broken dish, the pump cannot move water past it. Clean it, run a rinse cycle, and see if the problem is gone. This should be done every couple of months anyway.
2. The garbage disposal knockout
If the dishwasher drains into a garbage disposal and the disposal was installed or replaced recently, this is the answer more often than anything else. Every new disposal ships with a plastic knockout plug in the dishwasher inlet. If the installer did not remove it, the dishwasher has nowhere to drain. It will fill, run, and leave every drop behind.
Even when the knockout is out, a disposal full of ground food blocks the inlet. Run the disposal with plenty of cold water before you run the dishwasher. If the disposal itself is struggling, our post on disposal repair vs replacement covers that side.
3. The drain hose and the high loop
The drain hose leaves the dishwasher and should rise to the underside of the countertop before dropping to the disposal or the sink tailpiece. That high loop keeps dirty sink water from running back into the dishwasher. If the hose has slumped, been kinked behind the dishwasher when it was pushed into place, or is clogged with grease at the low point, drainage fails.
Pull the kick plate, look for kinks, and follow the hose under the sink. If it sags in a U below the cabinet floor, that U is full of sludge. Some jurisdictions and some manufacturers call for an air gap on the countertop instead of a high loop; if you have one and it is spitting water, it is clogged and needs cleaning.
4. The sink drain itself
A slow kitchen drain backs up into the dishwasher because the dishwasher pump is pushing against a column of water that cannot go anywhere. Grease is the usual reason in a kitchen line. Our guide to clogged drains covers what you can safely do yourself and when to stop.
5. The pump and the check valve
Only now does the appliance itself become the suspect. A drain pump can fail, and a check valve in the sump can jam with debris. You will usually hear a difference: a humming pump with no water movement, or no pump sound at all at the point in the cycle where it should drain. Some machines also have a drain solenoid or a float switch that can stick.
At this point the choice is an appliance repair or a new dishwasher, and the age of the unit decides it. A pump on a ten-year-old builder-grade dishwasher is rarely worth chasing.
Installing a new dishwasher properly
If you land on replacement, the install is where drainage problems get built in. We see hoses run flat under the cabinet, knockouts left in the disposal, and supply lines kinked by the machine being shoved into the opening. A proper install includes the high loop or air gap, a new supply line and stop, levelling the unit so the door seals, and anchoring it so it does not tip forward when the rack is loaded.
It is a normal part of our handyman and fixture work, and it fits easily into the same visit as a disposal or faucet swap.
Questions we get
The dishwasher drains but leaves a puddle at the end. Is that normal?
A small amount of water in the sump below the filter is normal and keeps the seals wet. Water sitting across the floor of the tub is not.
Why does water come back into the dishwasher after it finishes?
That is siphoning or backflow from the sink, which means the high loop is missing or the air gap is blocked. Fix the loop and it stops.
Is standing water a leak risk?
Not by itself, but a machine that cannot drain will eventually overflow at the door seal. Stop running it until the cause is found.
Need it looked at?
Wright Way Services handles kitchen drain, disposal and dishwasher hookups across Newnan, Coweta County and Fayette County. Call (770) 301-4638 or request service.
Open 24 hours · Newnan, GA
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Wright Way Services handles it all in one call — plumbing, remodeling, smart home installs and the whole punch list. Serving Newnan, Coweta County and the surrounding area.
