A dishwasher not draining almost always comes down to something blocking the path the water takes out of the tub: a dirty filter, a knockout plug that never got removed from a new garburator, a clogged air gap, a kinked drain hose or, less often, a tired drain pump. Work through those in order, cheapest first, and most people find the problem before they get anywhere near a tool.
This is the same seven-step checklist our technicians run on every dishwasher call across London, Woodstock and Kitchener. It covers how to deal with the standing water safely, what to check yourself, what hard water does to a drain in Southwestern Ontario, and the point where it is smarter to hand it over to a pro.
First, deal with the standing water safely
Before anything else, cut power to the dishwasher. Unplug it under the sink if you can reach the cord, or switch off its breaker.
Bail the tub with a cup and a towel, or a wet-dry vacuum if you have one. Water that has sat for a day or two will smell, so open a window. Notice what comes out: greasy grey water with food bits points to a filter or sump blockage, while clear water that simply will not leave usually means the hose, the air gap or the pump.
Dishwasher not draining? Fixes 1 to 4 solve most calls
1. Clean the filter
Pull out the bottom rack and look at the centre of the floor. Most dishwashers built in the last fifteen years have a twist-out cylindrical filter with a flat mesh plate around it. Turn it a quarter turn, lift it out, and rinse both pieces under hot water with a soft brush. A filter packed with rice, seeds and label glue is the single most common reason for standing water in a dishwasher. While it is out, feel inside the sump with a gloved hand for glass, fruit pits or toothpicks.
2. Check the garburator knockout plug
If your dishwasher drains into a recently installed garbage disposal, check this first. New disposals ship with a plastic plug inside the dishwasher inlet, and if the installer forgot to knock it out the dishwasher has nowhere to drain. Unplug the disposal, pull the dishwasher hose off the inlet nipple, and look for a plug you can tap out with a screwdriver.
On any disposal, run it for thirty seconds with cold water before starting the dishwasher, because a disposal full of food waste blocks the shared drain. If the garburator itself is jammed or humming, our garbage disposal repair page covers that separately.
3. Clear the air gap
Look beside the tap for a small chrome or plastic cylinder; not every home has one. Pull the cap off, remove the inner cover, and clear out anything sitting in it. If water spurts from the air gap while the dishwasher drains, the hose from the air gap to the drain is blocked.
4. Find the drain hose kink
Under the sink, follow the ribbed drain hose from the dishwasher to where it connects. It should rise in a high loop near the underside of the counter before dropping to the drain. If it sags, is pinched behind a pot or folded flat by a garbage can, straighten it, and check that the connection at the drain tee or disposal is not packed with sludge.
Fixes 5 to 7: sump, pump and control
5. Clear the sump and check valve
With the filter out, shine a flashlight into the sump. Many models have a small rubber flap or plastic check valve where the water exits; it can jam when a seed gets wedged under it. Free it gently with a wooden skewer, never a screwdriver, because the plastic housing below cracks easily.
6. Test the drain pump and impeller
The drain pump sits under the sump, and on many Bosch dishwashers and a few other brands you can reach it by removing a small cover in the sump floor and lifting the pump out. Check for anything wrapped around the impeller and that it spins freely. Bosch publishes cleaning steps for that cover in its Canadian support pages.
On most other brands the pump is only reachable from underneath, which means pulling the dishwasher out and laying it on its back. A pump that hums but moves no water has a stripped impeller or seized motor. One that makes no sound during the drain phase is either dead or not being told to run.
7. The control or a stuck cycle
Occasionally the pump is fine and the board never sends it power. Cut power at the breaker for five minutes, then run a cancel-drain cycle and listen for the pump. If it never runs and everything else checks out, the control board or wiring is the likely cause, and that is a job for a technician with a meter.
From the van: at least half of the dishwasher not draining calls we run in London end at the filter or a kinked hose behind the machine. Before you book anyone, pull the bottom rack, lift the filter out and look. It takes two minutes and it is the first thing we would do anyway.
Appliance Experts repairs dishwashers across London and Southwestern Ontario, 6 AM–9 PM, seven days a week — usually same day. The service call is free with the repair, and every job carries a 90-day parts and labour warranty.
Hard water in Southwestern Ontario and slow drains
Most of our service area sits on hard, mineral-heavy water, and it shows up inside dishwashers. Scale narrows the drain hose over time and glues food particles to the filter mesh, so a dishwasher that drains slowly rather than not at all is often just scaled up.
Run an empty cycle with a citric-acid dishwasher cleaner every month or two, and keep the filter clean. If you are also seeing cloudy glasses and a chalky film on the tub, our post on hard water and cloudy dishwasher glasses explains what is going on and what actually works to fix it.
When to call a pro
If the filter is clean, the hose is clear and the dishwasher still will not drain, the remaining suspects are the drain pump, the check valve, the control board and the wiring. Those repairs mean pulling the machine out and working around live connections and the water supply, and it is not worth flooding a kitchen floor to save a service call.
Also call if the dishwasher trips a breaker, if there is water on the floor rather than in the tub, or if it is still under manufacturer warranty. Our dishwasher repair service covers every major electric brand, and our London dishwasher repair team can usually get to you the same day. A drain pump replacement typically lands in the $180 to $360 range for a dishwasher repair in this region, with the diagnostic fee applied to the job.
Frequently asked questions
Why is there standing water in the bottom of my dishwasher?
The most common reason is a clogged filter or sump, followed by a kinked or blocked drain hose, a clogged air gap, and a knockout plug left in a new garbage disposal. A worn drain pump or a control fault is less common. Check the cheap items first, in that order.
Is it normal for a little water to stay in the dishwasher after a cycle?
A small amount of clean water in the sump around the filter is normal on many models; it keeps the pump seal wet. Water that covers the floor of the tub or reaches the bottom of the door is not normal and means the drain path is blocked.
Can I run the dishwasher if it is not draining?
It is better not to. Each cycle adds more water, the machine may abort with an error, and repeated attempts can overheat a jammed drain pump. Bail the tub, work through the checks, and run a cycle only once you have found and cleared the cause.
How much does it cost to fix a dishwasher that will not drain?
Filter and hose fixes cost nothing but a few minutes. If a technician needs to replace a drain pump or check valve, a typical dishwasher repair in Southwestern Ontario runs about 180 to 360 dollars including parts and labour, with the service call fee applied to the repair.
Does a garbage disposal affect dishwasher draining?
Yes. The dishwasher usually drains through the disposal, so a full or jammed disposal blocks it, and a new disposal with the knockout plug still in place blocks it completely. Run the disposal with cold water before each dishwasher cycle and confirm the plug was removed during installation.
The bottom line
A dishwasher not draining is one of the more forgiving appliance problems, because you can rule out the free fixes yourself in twenty minutes. Cut the power, bail the tub, clean the filter, check the disposal plug, the air gap and the hose, and only then think about the pump. If the pump or the board is the problem, that is where a technician earns the fee. Call Appliance Experts at (519) 900-3010 or book online, and take $35 off any completed repair while you are at it.