Why is Your Dishwasher Not Draining?

July 5, 2022
Dishwasher Repair

Dishwashers are one of the most convenient and most-used household appliances. So, if your dishwasher stops draining, having to do dishes by hand will significantly increase the amount of time you spend on household chores . Therefore, you want to resolve the issue as quickly as possible.

Here are the five most common reasons for the dishwasher not draining, with instructions to fix the problem.

Clogged dishwasher filter

Most dishwashers manufactured after 2010 have a removable filter in the dishwasher tub. If you don’t empty the filter or didn’t know it was there, that could be why your dishwasher isn’t draining.

Depending on the dishwasher model, the filter is usually cylindrical, and it’s removed with a one-quarter counterclockwise turn. Some dishwashers have a second coarse filter, which is usually a flat half-circle surrounding the cylindrical filter.

In some cases, the dishwasher’s bottom spray arm needs to be removed to access the filter, or the filter may have screws that first need to be removed.

Follow these steps to remove and clean the filter:

  1. Remove the bottom dish rack.
  2. Locate the filter and turn it counterclockwise, one-quarter turn.
  3. Lift the filter out of the dishwasher. If you see a coarse filter, it should lift out of the dishwasher too.
  4. Wash the filter(s) with a soft dish brush or sponge and dish soap. You can also use distilled white vinegar.
  5. Return the filter(s) to the dishwasher. Make sure the cylindrical filter locks into place by turning it clockwise, one-quarter turn.

Damaged or clogged pump impeller

The dishwasher’s pump impeller propels water out of the dishwasher when it’s draining. If the impeller is broken, clogged with food waste, or impeded with a foreign item like broken glass, the dishwasher won’t be able to drain properly.

Depending on the type of dishwasher, you may see the pump impeller when you remove the dishwasher filter. The impeller may have a cover over it, which has a tab to pull on to lift the cover off. Otherwise, you may have to access the sump underneath the tub.

Follow these steps to access and clean the pump impeller:

  1. Remove the dishwasher filter.
  2. Locate the pump impeller or remove the impeller cover.
  3. Remove any debris around the impeller.
  4. Check that the impeller isn’t damaged.
  5. Turn the pump impeller. It should turn freely. If the impeller doesn’t rotate, the pump has likely failed.

Failed drain pump

Depending on the type of dishwasher, it may have one pump or two (a circulation pump and a drain pump). If the dishwasher isn’t draining, the drain pump may have failed and will need to be replaced.

Accessing the pump depends on the type of dishwasher. You may be able to remove the sump cover in the dishwasher tub or from behind the dishwasher’s kickplate. Or you may need to put the dishwasher on its back to access the pump underneath the dishwasher tub.

Once you access the pump, test it with a multimeter for continuity (a continuous electrical path) to determine if it needs to be replaced.

Follow these steps to check the pump:

  1. Disconnect the power to the dishwasher and turn off the water supply.
  2. Access the drain pump.
  3. Disconnect the pump’s wiring harness and the hoses attached to it.
  4. Remove the pump from the dishwasher.
  5. Test the pump for continuity with a multimeter. If the pump fails the multimeter test, replace the pump.

Blocked drain hose

A blockage in the drain hose will stop the dishwasher from draining.

You can first check the end of the drain hose that connects to a P-trap, air gap, or garbage disposal underneath the sink. If the sink end of the drain hose isn’t blocked, the hose will need to be removed from the dishwasher by disconnecting it from the drain pump.

Forgetting to remove the drain plug in the garbage disposal, or a clogged garbage disposal or air gap are also potential causes for the drainage issue.

If the dishwasher is still draining, just not very well, running a long, hot wash cycle with a dishwasher cleaner or distilled white vinegar may unclog the drain hose.

Follow these steps to check the drain hose:

  1. Disconnect the power to the dishwasher and turn off the water supply.
  2. Disconnect the drain hose from the P-trap, air gap, or garbage disposal. If attached to a garbage disposal, make sure the drain plug has been removed and that the tube isn’t blocked.
  3. Remove any debris that you find.
  4. Depending on the type of dishwasher, remove the sump cover, kickplate, or put the dishwasher on its back to access the drain hose and pump.
  5. Disconnect the drain hose from the drain pump.
  6. Remove the drain hose from the dishwasher.
  7. Clean the drain hose with a drain snake and pour distilled white vinegar through the hose.
  8. Make sure the hose has no leaks. Replace the hose if it’s leaking.

Defective check valve flapper or check ball

Some dishwashers have a check valve flapper or a check ball that stops wastewater from returning into the dishwasher. If the flapper or ball gets stuck, water may not drain from the dishwasher.

The check valve flapper or check ball can usually be found in the dishwasher sump. Depending on the issue, you may be able to clean the flapper or reposition the check ball, or either component may need to be replaced.

Follow these steps to check the check valve:

  1. Disconnect the power and water supply to the dishwasher.
  2. Remove the bottom dish rack, spray arm, and filter.
  3. Remove the sump cover. Depending on the model, the entire spray arm assembly may need to be removed to access the four sump cover screws.
  4. Locate the check valve and check for a flapper or check ball.
  5. Clean the area and the check valve flapper. If you clean the check valve flapper, it may fix the problem. If the issue soon arises again, the flapper should be replaced. If the check ball is damaged, replace it.

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