Dishwasher Not Draining: Possible Causes and What to Check

Quick symptom summary

Find the row closest to what you’re seeing. These are possible meanings only.

Most likely categories of causes

These are the usual categories, from the simplest to the most involved.

The filter and sump. Food and debris collect in the filter and the sump beneath it. A clogged filter slows or blocks drainage and causes odor. It’s the most common cause and the easiest to clear.

The drain hose, air gap and disposal. The drain pump pushes water through a hose, sometimes through an air gap or a high loop, into the sink drain or a garbage disposal. A kinked or clogged hose, a clogged air gap or a disposal that’s blocked, or whose knockout plug was never removed after installation, will stop water leaving.

The household drain. If the kitchen sink is slow, the problem may be in the plumbing, not the dishwasher, and a plumber may be needed.

The drain pump. A pump can jam on debris such as broken glass or a fruit pit, or wear out. A hum without water moving, or silence at the drain step, fits this pattern.

Controls and switches. A control board fault or a float switch problem may stop the drain cycle. A code often accompanies it.

Safe checks you can make

These checks are safe when the power is off. They’re not a diagnosis.

1. Turn off power to the dishwasher at the breaker.
2. Scoop out standing water with a cup and towels.
3. Remove and rinse the filter, following your manual.
4. Look in the sump beneath the filter for debris, and remove anything you can see, wearing gloves.
5. Check the kitchen sink: is it draining normally? Run the disposal if you have one.
6. Check the drain hose under the sink for kinks, and if you have an air gap, make sure it isn’t clogged.
7. If the dishwasher is new, check whether the disposal’s knockout plug was removed.
8. Restore power and run a drain cycle to test.
9. Note any error code and photograph the model label.

Stop and call a technician if water is near electrical connections or outlets, you smell burning or see scorch marks, the dishwasher trips the breaker, the filter and sump are clear and it still won’t drain, you’d need to remove panels or reach the pump or wiring, or the kitchen sink is blocked, in which case a plumber may be needed. Don’t put your hands in the pump area without disconnecting power, and don’t pour drain chemicals into a dishwasher.

How a technician narrows the problem

A technician narrows the problem in steps:

1. Ask when it started, whether the sink is slow and what was tried.
2. Identify the brand, model, serial number and installation type.
3. Check the filter, sump, hose, air gap and disposal connection.
4. Test the drain pump and its power supply.
5. Check the float switch and control signals.
6. Confirm the cause before recommending a repair.

Relevant components and terms

Repair considerations

What tends to shape a drain repair:

• The cause. Cleaning a filter is different from replacing a pump or a board.
• Plumbing versus appliance. If the sink drain is the problem, a plumber may be the right call.
• Access. Some repairs need the dishwasher pulled forward from the cabinet.
• Parts availability. An ordered part adds a step.
• Cost. It depends on the confirmed cause. Ask for the cause and full cost before approving work.

Common mistakes with a dishwasher that won’t drain

Skipping the filter. It’s the most common cause and the easiest fix. Ignoring the sink. A slow sink points to the household drain. Using drain chemicals. They can damage the dishwasher. Reaching into the pump area with the power on. Turn off power at the breaker first. Forgetting the disposal knockout plug after a new installation.

Repair or replace?

A clog, a hose problem or a single failed pump on an otherwise sound dishwasher is usually worth repairing. Replacement is more likely when a drain problem comes with a cracked tub or several other failures on an older unit. A technician can advise after diagnosis, and there’s no obligation to repair.