Dishwasher Not Draining? 6 Things to Check Before You Call
By Mike Holt, NJ Master Plumber · August 2, 2024 · 3 min read · Updated November 1, 2026
Quick answer
Start with the filter at the bottom of the dishwasher, which clogs with food. Then run the garbage disposal and check the drain hose under the sink for kinks. If you have an air gap, have a professional investigate it. If the kitchen sink is also slow, the shared drain line may be clogged and need a plumber.
- Difficulty
- Simple checks. Air gaps and drain connections need a professional
- Time
- 20 to 40 minutes
- You need
- Towels, a cup or sponge, flashlight
Rather not risk it? A licensed plumber can handle this for you, with written upfront flat-rate pricing options before any work starts.
When a dishwasher won't drain, the problem is often in the plumbing under the sink and not the dishwasher itself. Most of these checks take a few minutes and no tools. Anything past looking or cleaning the filter goes to a professional. Scoop the standing water out with a cup and a towel first, so you can see what you're doing.
How to fix a dishwasher that won't drain
Step 1: Clean the filter
Pull out the bottom rack. Most dishwashers have a round filter in the floor of the tub that twists out by hand. Rinse it under the faucet and scrub the mesh with an old toothbrush. Wipe out the area underneath, then lock the filter back in. A clogged filter is the most common reason for standing water.
Step 2: Run the garbage disposal
Most dishwashers drain through the garbage disposal. If the disposal is full of food, the dishwasher water backs up. Run cold water and turn the disposal on for 20 to 30 seconds, then run a short dishwasher cycle.
Step 3: New disposal? Ask about the knockout plug
If the problem started right after a new disposal went in, the knockout plug may still be in the dishwasher inlet on the side of the disposal. Checking it means disconnecting the power and taking off the drain hose, so call us or your installer.
Step 4: Check the drain hose
Look under the sink. The corrugated drain hose should run without kinks. Make sure nothing stored under the sink is crushing it. Dishwasher drain connections must follow appliance instructions and applicable NJ plumbing requirements, so if the routing looks wrong, have a plumber look at it.
Step 5: Look at the air gap
Some kitchens have an air gap, a small chrome cap on the back of the sink next to the faucet. Not every installation has one, and what's required depends on the appliance instructions and NJ plumbing requirements. If yours spills water when the dishwasher drains, we recommend a professional investigation of it. Don't take it apart.
Step 6: Test the kitchen sink drain
Fill the sink a few inches and let it drain. If it drains slowly, or water bubbles up in the sink while the dishwasher runs, the drain line the two share is clogged. Don't pour chemical drain cleaner into it. That's a job for a plumber. See our drain cleaning page.
Plumber or appliance repair?
Call a plumber if the kitchen sink is slow too, water backs up into the sink, or something is leaking under the sink. Call an appliance repair technician if the sink drains fine, the filter and hose are clear, and the dishwasher still won't pump water out. A humming sound with no draining, or an error code on the display, usually means the dishwasher's drain pump has failed.
Keep it from happening again
- Scrape plates into the trash. Your dishwasher doesn't need pre-rinsed dishes, but it can't handle bones, rice and bits of paper labels.
- Clean the filter once a month.
- Run the disposal before you start the dishwasher.
- Keep grease out of the sink. Our post on why oil is bad for your drains explains why.
Need help with a clogged kitchen drain? Call 908-873-6686. Written upfront flat-rate pricing options. You choose.
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Stop and call us if
- The kitchen sink is slow or backs up too, or water comes up in the sink when the dishwasher drains.
- Water is leaking under the sink or onto the floor.
- Water spills from the air gap, or the drain hose needs to be replaced or rerouted.
- You just installed a garbage disposal and the dishwasher stopped draining.
Call 908-873-6686.
Michael Holt
Owner and operator of Plumbing Doctor, NJ Master Plumber (Lic. #36BI01345600) and U.S. Marine Corps veteran.
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