You open the dishwasher at the end of a cycle and there’s a pool of grey water sitting in the bottom. The dishes might be clean, or they might be covered in a gritty film. Either way, a dishwasher not draining is one of the most common calls we get in Toronto, and the good news is that most drain problems are caused by something you can reach and clear yourself in about 20 minutes.
This guide walks you through the fixes in the same order a technician works through them: the quick, free checks first, then the parts that take a little more effort, and finally the faults that need a repair visit.
Before You Start: Power Off and Bail the Water
Water and electricity don’t mix, so do these two things before you put your hands inside the tub:
- Cut the power. Unplug the dishwasher if you can reach the plug (often under the sink), or switch off its breaker at the panel. Turning it off at the control panel is not enough.
- Remove the standing water. Pull out the bottom rack, then use a cup or plastic container to bail the water into a bucket. Finish with old towels or a sponge. Don’t use a wet/dry shop vac on the drain pump area unless you’re sure the power is off.
Watch for broken glass in the bottom of the tub. A small shard is one of the more common things we find jammed in a drain pump.
Also check one simple thing: did the cycle actually finish? If the dishwasher was interrupted mid-cycle (a power blip, someone opening the door, or a cancelled cycle), it’s normal for water to be left behind. Try running a short rinse or “cancel/drain” cycle first. Many models drain when you press and hold the start button or cancel button for a few seconds; check your owner’s manual for the exact method on yours.
Fix 1: Clean the Filter and Sump
This is the number one cause of a dishwasher not draining, and it’s the first thing we check on every service call. Most modern dishwashers have a manual filter that’s meant to be cleaned by the owner, and many people don’t know it’s there.
- Pull the bottom rack all the way out.
- Find the filter at the bottom of the tub, usually under or near the lower spray arm. It’s often a cylinder you twist a quarter turn counter-clockwise and lift out, with a flat mesh screen underneath.
- Rinse both parts under warm running water. Use a soft brush or old toothbrush to remove grease, food bits, labels and seeds. Avoid wire brushes, which can tear the mesh.
- With the filter out, look into the opening (the sump). Remove anything sitting in there: bits of glass, bones, fruit pits, twist ties or plastic.
- Reinstall the filter and lock it fully in place. A filter that isn’t seated properly can let debris through to the pump.
Bosch, for example, recommends checking and cleaning the filter regularly as part of normal care. A good habit for most households is to look at it every few weeks, or more often if you don’t rinse plates before loading.
Fix 2: Check the Drain Hose, High Loop and Air Gap
If the filter was clean, the next place water gets stuck is the drain hose that runs from the dishwasher to your sink drain.
Look for kinks
Open the cabinet under the sink and follow the ribbed drain hose as far as you can. If the dishwasher was recently installed or pushed back into place, the hose may have been crushed or kinked behind it. Straighten any bends you can reach.
Check the high loop
The drain hose should rise up and be fastened high under the counter (called a “high loop”) before it drops down to the sink drain or disposal. This stops dirty sink water from flowing back into the dishwasher. If the hose is lying on the cabinet floor, the dishwasher may refill with sink water or drain poorly. Use a zip tie or hose clamp to secure it as high as possible under the counter.
Clean the air gap (if you have one)
Some kitchens have a small chrome or plastic cap on the countertop next to the faucet. That’s an air gap. Pull or twist off the cover, remove the inner cap, and clear out any gunk with a small brush or paper towel. A clogged air gap often shows itself by water spilling out of it onto the counter while the dishwasher drains.
Clear the hose itself
If you’re comfortable doing it, you can disconnect the hose at the sink end (have a bucket and towels ready), and blow through it or flush it with water to check that it’s clear. If you can’t get water through it easily, it’s blocked, and it may be simpler to replace than to clean.
Fix 3: The Garbage Disposal Knockout Plug and the Sink Drain
The dishwasher drains into the same pipe as your kitchen sink, so a slow sink means a slow dishwasher.
- New garbage disposal? If the dishwasher stopped draining right after a disposal was installed, this is almost certainly the cause. New disposals come with a plastic “knockout plug” sealing the dishwasher inlet. It has to be knocked out during installation, and it’s easy to forget. With the disposal unplugged or switched off at the breaker, remove the hose from the disposal’s inlet and look inside. If you see a solid plastic wall, it needs to be knocked out (and the loose piece removed from inside the disposal).
- Run the disposal. If you have a disposal, run it for a few seconds with cold water before you start the dishwasher. Food waste in the disposal can block the dishwasher’s drain inlet.
- Test the sink. Fill the sink partway and let it drain. If it’s slow, the clog is in the household plumbing, not the dishwasher. Clear the sink drain first, then try the dishwasher again. Avoid pouring chemical drain cleaners into the dishwasher itself, as they can damage seals and parts.
Fix 4: The Drain Pump and Check Valve
If the filter, hose and sink drain all check out, the problem is likely the drain pump or the check valve that stops water from flowing back in.
Listen first
Start a cycle, then cancel or skip to drain, and listen closely:
- A normal humming or whooshing sound with water going down means the pump is working, and the restriction is somewhere downstream.
- A hum with no water moving often means something is jamming the pump impeller.
- A grinding or rattling noise can mean debris (often glass) is in the pump.
- Complete silence during drain can point to a failed pump motor, a wiring problem or a control fault.
Clear the pump cover
On many models you can reach the pump impeller from inside the tub. With the power off and the filter removed, look for a small cover (often a clip-on plastic piece) in the sump. Remove it and gently check the impeller blades with a gloved finger or a plastic utensil. If they don’t turn freely, remove the debris. Be careful: glass fragments are sharp. Bosch’s own guidance describes a similar process for its dishwashers, and your manual will show where the cover is on your model.
The check valve
The check valve is a small flap or ball in the drain path that lets water out but not back in. If it sticks closed, water can’t leave. If it sticks open, drained water can flow back in. It’s usually located where the drain hose connects to the pump, and reaching it typically means pulling the dishwasher out or removing the kick plate. This is the point where many people decide to call a technician.
Error Codes That Mean a Drain Fault
Many dishwashers will tell you there’s a drain problem with an error code. A few common ones:
- Bosch E24 / E25: E24 usually points to a drain blockage (filter, hose or sink drain), while E25 usually points to something blocking the drain pump itself. See our full list of Bosch dishwasher error codes.
- LG OE: A drain error, meaning the dishwasher couldn’t drain within the expected time. Our guide to LG dishwasher error codes covers the rest.
- Whirlpool, KitchenAid and Maytag: These brands use different code formats depending on the model and age, and some older models flash the cycle lights in a pattern instead of showing a code. Check the tech sheet that’s usually tucked behind the kick plate or inside the door panel, or your owner’s manual.
A drain error code doesn’t always mean the pump is broken. In most cases the same steps above (filter, hose, sink drain, pump cover) clear the fault. After fixing the cause, you may need to reset the dishwasher by turning off power at the breaker for a minute or two.
When to Call for Repair
Some drain problems need proper diagnosis and tools. It’s time to call a technician if:
- You’ve cleaned the filter, checked the hose and confirmed the sink drains well, and water still sits in the tub.
- The pump hums, grinds or stays silent, and you can’t clear it from inside the tub.
- The drain error code keeps coming back after a reset.
- There’s water leaking onto the floor or under the dishwasher.
- You smell burning or see scorched wires, or the breaker trips when the dishwasher drains. Stop using it and leave the power off.
- Getting to the pump or check valve means pulling the dishwasher out from under the counter, disconnecting the water line or opening electrical panels, and you’re not comfortable doing that.
For other dishwasher troubles such as poor cleaning or noise, our post on common dishwasher problems and solutions is a good next read.
Quick Recap
- Turn off the power, bail the water and make sure the cycle actually finished.
- Clean the filter and check the sump for debris.
- Straighten the drain hose, set a high loop and clean the air gap.
- Check the disposal knockout plug and make sure the sink drains freely.
- Clear the pump impeller, then consider the check valve.
- Call a pro if the pump is noisy or silent, the code keeps coming back, or there’s a leak.
Need Help With a Dishwasher That Won’t Drain?
If you’ve worked through these steps and your dishwasher still won’t drain, I-Fix Appliance Repair can help. Our technicians repair all major dishwasher brands across Toronto, North York, Scarborough and Etobicoke, and we’ll give you an honest answer about whether a repair makes sense. Visit our dishwasher repair page or contact us to book a visit.