Troubleshooting
Why a dishwasher won’t drain
A shallow pool of water at the bottom of the tub after a cycle is one of the most common dishwasher complaints. In most homes it is not a failed motor — it is a blockage somewhere between the filter and the drain connection under the sink. Working through the path in order saves time and usually avoids a service call.
Before you start
Switch the dishwasher off at the wall outlet or the breaker before reaching inside. Standing water can be drained with a cup and a sponge; lay towels on the floor first.
What is actually happening
At the end of a cycle a drain pump pushes used water out through a hose, often up to an air gap or a high loop, and then into the sink drain or a garbage disposal. If water cannot complete that journey it falls back into the tub. The blockage is usually at the first narrow point: the filter.
Step-by-step check
- Clear the standing water. Bail out what you can with a cup, then soak up the rest. A dry tub makes the filter easier to inspect.
- Remove and rinse the filter. Most modern units have a twist-out cylindrical filter in the floor of the tub. Rinse it under a tap and clear any food, glass or labels from the mesh.
- Check the sump and spray arm. With the filter out, look for debris in the recess beneath it and make sure the lower spray arm turns freely.
- Inspect the drain hose. Under the sink, feel along the corrugated hose for kinks. A hose crushed behind a stored bucket is a frequent culprit.
- Look at the air gap. If your counter has a small chrome cylinder beside the faucet, lift its cap and clear any sludge. This part is common in Canadian kitchens fitted with one.
- Run a short cycle. Restore power and run the rinse-only setting to confirm the tub now empties.
If there is a garbage disposal
When the dishwasher drains into a disposal unit, a freshly installed disposal can still have its knockout plug in place, blocking the dishwasher line entirely. If the problem began right after a disposal was installed, that plug is worth checking.
Hard water and cold climates
Across much of the Prairies and parts of Ontario, mineral-rich water leaves scale that can narrow the filter mesh over months. In unheated spaces a drain line can also be slowed by cold. Neither is a fault in the appliance, but both shorten the interval between filter cleanings.
When to stop and call a technician
If the filter, hose and air gap are clear but the tub still holds water, the drain pump or control board may be at fault. These involve mains electricity and water together; a licensed appliance technician is the safer choice.
Upkeep that prevents a repeat
- Rinse the filter roughly once a month, more often with heavy use.
- Scrape plates instead of pre-rinsing so large debris never enters the tub.
- Run an empty hot cycle periodically to clear grease from the sump.