Most built-in dishwashers drain through the garbage disposal, so start there: run the disposal to clear any clog, then clean the cylindrical filter in the tub floor and remove standing water from the sump. If the unit is newly installed and never drained, the disposal's knockout plug was probably left in, which blocks drainage completely.
Quick checks
- Run the garbage disposal for several seconds. A clog there backs water up into the dishwasher.
- New install that has never drained once? Suspect the disposal knockout plug first.
- Pull the bottom rack and twist out the filter in the tub floor. Rinse and reseat it.
- Scoop standing water out of the sump with a cup, then feel around the drain opening for food, glass, or a stuck label.
- Look behind and under the unit for a kinked or crushed drain hose.
Work through it in order
The fixes below go from most common and easiest to least common. Do them in sequence and test a short cycle after each one, so you know which step solved it.
- Run the disposal. Most dishwashers share a drain line with the garbage disposal. Turn the disposal on with water running for ten seconds to clear food, then run the dishwasher's drain or rinse cycle and watch whether the water leaves.
- Rule out the knockout plug (new installs only). When a dishwasher or disposal is brand new and has never drained, the most common miss is the disposal's knockout plug. The plug seals the disposal's dishwasher inlet from the factory and has to be tapped out before water can pass. Disconnect power to the disposal, reach into the inlet with a screwdriver, tap the plug out, and remove the loose piece. Whirlpool calls this step critical for draining and a common misdiagnosis.
- Clean the filter. In normal use this is the number one cause. Remove the bottom rack, twist the cylindrical filter counterclockwise, lift it out, and rinse it under hot water. Scrub gently with a soft brush to clear grease and food, then drop it back in and twist to lock. A clogged filter looks fine at a glance but chokes the flow. Our guide on the dishwasher filter when dishes come out dirty walks through the same part.
- Clear the sump. With the filter out, scoop the standing water from the well at the bottom with a cup or sponge. Then clear anything sitting around the drain opening: a shard of glass, a chunk of food, or a soaked-off jar label can all block the pump.
- Check the drain hose. Pull the unit out enough to see the hose, or look under the sink where it connects. A kink, a crush from being shoved against the cabinet, or a sag full of standing water all stop drainage. Confirm the hose is clamped tight at both ends.
- Inspect the air gap or high loop. If you have a small chrome cylinder on the counter beside the faucet, that is the air gap. Pop the cap, lift the cover, and clean out any gunk inside. If there is no air gap, the drain hose should loop high under the counter before dropping to the disposal, which keeps dirty sink water from flowing back. Which one you have depends on local plumbing code.
Water sits at the bottom after every cycle
A shallow pool of clean water in the sump is normal between cycles on some models. A full pool of dirty water means the drain step failed. Run the disposal, then clean the filter and sump as above. If standing water comes back after a clean cycle, the hose or pump is the next suspect.
It drains slowly or only partway
Partial draining usually points to a partial clog rather than a full failure. A greasy filter, a sagging hose holding water, or a dirty air gap each slow the flow without stopping it. Clean all three and watch whether the cycle ends with a dry sump.
Brand new dishwasher that has never drained
Go straight to the knockout plug. A unit that drained fine and then stopped has a clog or a worn part; a unit that has never once pushed water out almost always has the plug still in place. If you have a Bosch, the routine is a little different, so see why a Bosch dishwasher will not drain.
When to call for service
If the disposal runs clear, the knockout plug is out, the filter and sump are clean, the hose is unkinked and clamped, and the air gap or high loop is clear, and the unit still will not drain, the drain pump or a control board part has likely failed. Those are sealed electrical components inside the base. Call the manufacturer or a qualified appliance technician rather than opening the pump housing yourself. If the unit is under warranty, do not start disassembly that could void it.
How to keep it draining
Almost every drainage call traces back to food and grease building up where water has to pass. A few habits keep the path clear:
- Scrape plates into the trash before loading. You do not need to pre-rinse, but knock off bones, peels, and large scraps.
- Clean the filter monthly, or every couple of weeks if you run the dishwasher daily or skip rinsing.
- Run a hot empty cleaning cycle with a dishwasher cleaner or a cup of white vinegar roughly once a month to cut grease in the sump and hose.
- Run the disposal before the dishwasher so the shared line starts clear.
If odors come with the standing water, a clean filter usually fixes both at once. See why your dishwasher smells and how to clear it.
Common questions
Why does my new dishwasher have water at the bottom and will not drain?
On a brand new dishwasher or disposal, the disposal's knockout plug was probably left in. It seals the inlet from the factory and must be tapped out before water can drain. This is the single most common miss on fresh installs.
Can I pour vinegar or baking soda down a dishwasher to unclog it?
A hot cleaning cycle with white vinegar helps cut grease and keeps the sump clear, but it will not move a solid clog or a stuck knockout plug. Clear the disposal, filter, and sump physically first, then use vinegar as upkeep.
Why does dirty water back up into my dishwasher from the sink?
That is backflow, and it points to a missing or misrouted high loop, or a clogged air gap. Clean the air gap if you have one. If you do not, make sure the drain hose loops high under the counter before dropping to the disposal.
Is standing water in the bottom of a dishwasher normal?
A small amount of clean water in the sump is normal on some models between cycles. A full pool of cloudy, food-filled water after a finished cycle is not, and means the drain step failed.
Good maintenance rhythm
- Ongoing: scrape plates before loading and run the disposal before starting the dishwasher.
- Monthly: clean the cylindrical filter and run a hot empty cycle with dishwasher cleaner or white vinegar.
- Yearly: pull the unit out far enough to check the drain hose for kinks and confirm the clamps are tight.