Dishwasher Not Draining
You open the dishwasher expecting clean dishes and instead there's a pool of murky water at the bottom. This is almost always a blockage somewhere in the drain path, not a dead dishwasher. Let's track it down.
What to Check Before You Call Someone
Check the garbage disposal knockout plug
If you recently installed a new garbage disposal, this is very likely your problem. Dishwashers drain through the garbage disposal, and new disposals come with a knockout plug that blocks the dishwasher drain port. It has to be physically removed during installation... and a lot of people (and some installers) forget.
Fix: Turn off power to the disposal. Reach into it with a screwdriver and knock out the plastic plug from the inside. Fish the plug out so it doesn't cause a jam. This is the number one cause of drainage problems after a disposal install.
Check the drain hose for kinks
Pull the dishwasher out slightly or look under the sink where the drain hose connects. The hose runs from the dishwasher to either the garbage disposal or an air gap on the sink. If it's kinked, pinched, or sagging, water can't flow out.
Fix: Straighten any kinks. Make sure the hose has a high loop (goes up near the countertop before going down to the disposal connection). This high loop prevents dirty water from flowing back into the dishwasher. If the hose is old and cracked, replace it... they're a few bucks at the hardware store.
Clean the air gap
If you have a small chrome or stainless cylinder on your sink (usually next to the faucet), that's the air gap. It prevents backflow into the dishwasher. When it gets clogged with debris, water backs up.
Fix: Twist off the top cap and the inner cover. Clean out any gunk. Use a stiff brush or pipe cleaner to clear the passages. While you're there, check that the hose from the air gap to the disposal isn't clogged either.
Clean the dishwasher filter and trap
Most modern dishwashers have a removable filter at the bottom of the tub, usually under the lower spray arm. When it gets packed with food debris, grease, and gunk, drainage slows to a crawl.
Fix: Remove the lower spray arm if needed, then twist out the filter. It usually turns counterclockwise. Clean it thoroughly with hot water and a brush. Some have a coarse filter and a fine mesh filter... clean both. Put them back and run a short cycle to test.
Check the drain pump
If you've cleared every blockage and the dishwasher still won't drain, the drain pump might have failed. You might hear it trying to run (a buzzing sound at the end of the cycle) or complete silence when it should be draining.
Fix: A drain pump replacement is a $50-100 part and is doable as a DIY project if you're comfortable pulling the dishwasher out and working underneath it. There are model-specific videos for most dishwashers. If this feels like too much, a repair tech will charge $150-250 for this fix.
When It's Time to Replace
Dishwasher drainage issues are almost always fixable without replacement. The exceptions: if the tub itself is cracked and leaking, if the control board is dead and the drain pump won't activate, or if the machine is 12+ years old and this is just the latest in a string of problems. At that point, a new dishwasher ($400-700 installed) is the better investment.
Read our full Dishwasher replacement guide →When to Call a Professional
Call a plumber if the kitchen sink also isn't draining (the problem is in your main drain line, not the dishwasher). Call an appliance tech if the drain pump has failed and you're not comfortable replacing it yourself. And if the dishwasher trips a breaker or you see any electrical issues, stop and call someone.
This guide is for informational purposes. For gas leaks, electrical issues, or emergencies, call a licensed professional immediately.