Dishwasher Not Draining Properly? The Causes and Solutions

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If your dishwasher is not draining, there is likely a blockage in the drain hose, or the pump may be defective. However, you don’t need to call a technician or plumber straight away, as you may be able to fix the issue yourself. This guide gives you all the likely causes and solutions, starting from the most common and easiest to fix.

Cause: The filter is clogged

Most dishwashers have a filter located in the dishwasher tub underneath the spray arm. If you are not in the habit of emptying the filter, debris may be clogging it and restricting the dishwasher’s ability to drain.

Solution: Empty the filter

  1. Open the dishwasher door and remove the bottom dish rack, cutlery basket, and spray arm. Spray arms are often not secured and can be lifted out of the dishwasher. If the spray arm is secured, it may need to be unscrewed or a tab depressed to remove it.
  2. Locate the filter and turn it counterclockwise to remove it from the dishwasher
  3. Empty out the filter and wash in the sink with warm, soapy water. A soft toothbrush can be used to clean the filter properly without damaging the filter.
  4. Return the filter to the dishwasher.

Cause: The garbage disposal is blocked

If your dishwasher connects to the garbage disposal, it may be blocked, which can affect the dishwasher’s ability to drain. Alternatively, if the dishwasher has recently been connected to the garbage disposal, the drain plug may not have been removed. If you are not keen on disconnecting the drain hose, you can try pouring a non-toxic drain cleaner into the disposal.

Solution: Clear the blockage and remove the plug

  1. Check the garbage disposal for a blockage, and run the disposal or remove the debris if there is a blockage
  2. Locate the drain hose that connects to the garbage disposal (usually underneath the sink)
  3. Depending on the connection, either unscrew or unclamp the drain hose from the garbage dispenser. Be prepared for some water to spill.
  4. Check that the drain plug has been removed
  5. Remove any debris that you find
  6. Make sure the drain hose is properly secured when you reconnect it.

Cause: The drain hose is clogged

If the dishwasher is not draining, a clogged drain hose is often responsible. If you are lucky, you will be able to clear the blockage with vinegar and baking soda. Otherwise, the drain hose will need to be disconnected, which can involve disassembling the dishwasher. If you need to disassemble the dishwasher, you will want to check the drain pump, and possibly the check valve (depends on the dishwasher) while you have access to it.

Solution: Unclog the drain hose

  1. Remove the bottom dish rack, dish basket, spray arm, and filter from the dishwasher.
  2. Remove as much water as you can from the dishwasher tub.
  3. Pour 1 ½ cups of baking soda and 1 ½ cups of white vinegar into the dishwasher tub; around the drain.
  4. Let it sit for 15 minutes.
  5. Rinse the area with boiled water.
  6. Run a rinse cycle to see if the issue has been resolved.

If the issue remains, the drain hose needs to be disconnected and removed from the dishwasher. Once the drain hose has been disconnected and removed, it can be unclogged with a drain snake tool, or flushed out with water.

Removing the drain hose usually involves dismantling the dishwasher. However, disconnecting the drain hose where it connects underneath the sink may reveal the blockage, saving you from having to dismantle the dishwasher. See dishwasher dismantling instructions below (under checking the pump).

Cause: The pump is defective or clogged

Occasionally, the dishwasher’s drain pump can become clogged, or the pump can fail either mechanically or electronically. If the drain hose isn’t clogged, a problem with the pump is the next most likely cause of the drainage issue. A multimeter is needed to test the pump for an electrical issue.

You should be able to determine if the pump has failed by listening for the pump to activate when the dishwasher enters the drainage cycle. If you cannot hear the pump or the pump sounds like it is struggling and not operating normally, the pump most likely needs to be replaced.

Accessing the pump depends on the type of dishwasher. You may be able to access the pump by removing the covers in the tub and sump, but most likely, the dishwasher’s kick plate needs to be removed, and the dishwasher needs to be put on its back to access the pump underneath the sump.

Solution: Check the pump is working, replace it if defective

  1. Disconnect the power to the dishwasher.
  2. Remove the dishwasher’s kick plate.

Depending on the dishwasher, you may now be able to access and remove the pump. If you cannot access and remove the pump, the dishwasher needs to be moved.

  1. Turn off the water to the dishwasher and disconnect the drain hose.
  2. With the kickplate removed, open the junction box and remove the wiring nuts to disconnect the wires (for hardwired dishwashers).
  3. Remove the mounting nut that secures the dishwasher underneath the kitchen cabinet.
  4. Pull the dishwasher out and carefully place the dishwasher on its back.
  5. Locate the pump underneath the dishwasher.
  6. Disconnect the hoses connected to the pump.
  7. Check the pump and hoses for a blockage or damage, like a broken impeller.
  8. Disconnect the pump’s wiring harness.
  9. Remove the pump from the dishwasher.
  10. Check the pump for continuity with a multimeter. After testing both terminals, test the grounding connection by placing a probe on one terminal and the other probe on bare metal (repeat for the other terminal).

If the pump is damaged or fails the multimeter continuity test, it needs to be replaced to fix the drainage issue.

Other less likely causes

If the above causes and solutions have failed to fix the problem, one of the following components may be defective. Not all dishwashers have these components, and the locations can vary. Check the dishwasher’s manual to see if the component applies to your dishwasher and its location. If the component is defective, it will most likely need to be replaced.

  • Timer that controls the pump motor (possibly the drain solenoid as well)
  • Drain solenoid
  • Check valve flapper
  • Check valve piston and nut assembly
  • Check ball (part of some check valves)
  • Water pump belt
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