Dishwasher Not Draining: Six Checks Before You Call a Repair Tech
Water sitting in the sump after a cycle almost always means a restriction downstream of the pump, not a dead pump. Work outward from the tub — cheapest and easiest first.
Before anything else: switch the dishwasher off at the breaker. You will be reaching into standing water near a heating element.
1. Bail out the water
Scoop what you can with a cup, then soak the rest up with towels. You need the sump dry to see what is happening.
2. Pull and rinse the filter
Nearly every machine built in the last fifteen years has a cylindrical filter in the floor of the tub that twists out by hand. Grease and label paper build up into a mat that water cannot pass. Rinse it under hot water with a brush.
3. Clear the sump and impeller
Under the filter is the sump. Feel around for glass chips, seeds, and fruit stickers. If you can reach the impeller, turn it by hand — it should move freely.
4. Check the drain hose for a kink
The hose runs from the pump to your sink drain or disposal. If the machine was recently pushed back into its cabinet, the hose is the first thing to get pinched behind it.
5. Clear the disposal and air gap
If the drain hose feeds a garbage disposal, run the disposal — a plug of waste in its inlet will back the dishwasher up. If you have an air gap (the small chrome cylinder on the sink deck), pop the cover and clear it.
6. Confirm the high loop
The drain hose must rise to just under the countertop before dropping to the drain. Without that loop, dirty sink water siphons back into the tub. Strapping the hose up under the counter is a five-minute fix.
What is left after that
If all six are clear and it still holds water, you are looking at the drain pump or the check valve. A pump is a moderate DIY job on most brands, but if the machine is out of warranty and more than about eight years old, get a quote on replacement before buying parts.
Testing the drain pump
If all six checks above are clear, the pump is next. It is a separate motor from the wash pump on nearly every machine, and it fails in two ways.
It hums but moves nothing — the impeller is jammed or the bearing has seized. Sometimes a piece of glass or a fruit stone is wedged against it, in which case clearing it is the whole repair.
It is silent — the motor windings have failed, or it is not getting power. With the machine unplugged, you can measure the pump’s resistance at its connector: most read somewhere between 15 and 200 ohms depending on design, and an open circuit means the motor has failed. Check the figure for your model rather than the range here.
Getting to the pump usually means tipping the machine onto its back after disconnecting the water, drain, and power. Put towels down; there is always water left in the sump.
The check valve
Many dishwashers have a small rubber flap or ball valve between pump and drain hose to stop discharged water flowing back in. When it perishes or sticks open, the machine drains and then partially refills itself from the hose.
The signature is a machine that drains correctly during the cycle but has an inch of water in the bottom hours later. It is a cheap part and usually accessible with the pump.
When the control is at fault
If the pump tests good and gets no power during the drain portion of the cycle, the fault is upstream: the control board, or on older machines a timer. Before concluding that, check the float switch — a small plastic float in the tub floor that tells the machine there is water present. If it sticks in the raised position the machine may refuse to fill; stuck down, it may not know to drain. Lift it by hand and feel for free movement, and clean around it.
Standing water is not always a fault
Two normal cases people mistake for a fault:
- A small amount of clean water in the sump between cycles is by design on many machines. It keeps the pump seal from drying out. An inch of clear water is fine; dirty water with food debris is not.
- A brand-new installation that will not drain at all is usually the plug still in the disposal inlet. New garbage disposals ship with a knock-out plug in the dishwasher connection, and it has to be removed with a screwdriver before the dishwasher is connected. This catches a lot of people.
Preventing the repeat
Most drain faults are accumulation, so the habits are simple:
- Scrape plates; do not pre-rinse them spotless. Modern detergents need some soil to work against, but bones, stickers, and large debris belong in the bin.
- Clean the filter monthly. It takes a minute and it is the single most effective thing you can do.
- Run a hot cycle with dishwasher cleaner or citric acid every few months to clear grease from the sump and hose.
- Run the hot tap at the sink before starting the machine so it fills with hot water rather than the cold sitting in the pipe. Grease drains rather than congealing.
A quick reference
| Symptom | Most likely cause |
|---|---|
| Standing dirty water after every cycle | Filter or sump blocked |
| Drains partly, leaves an inch | Check valve, or drain hose not looped |
| Never drains, pump silent | Pump motor, control, or float switch |
| Never drains, pump hums | Impeller jammed |
| Drains, then refills between cycles | Check valve, or hose siphoning |
| Brand new install, no drain at all | Disposal knock-out plug still in place |
| Water backs up into the sink | Shared drain blockage, not the machine |