How to unclog a dishwasher drain

Gray water still sitting in the tub when a cycle ends is stuck somewhere along its exit, and the culprit is one of four spots: the filter basket in the tub, the drain pump, the hose behind the machine, or the sink drain it connects to. Work through them in that order, since each takes longer than the one before. If several sinks drain slowly too, the clog is deeper, and drain cleaning and clogs is the better starting point.

Before reaching in, unplug the machine or flip its breaker, then ladle out what remains using a mug and a towel.

What traps wash water inside a dishwasher?

A clogged filter or drain hose is the usual reason. Food bits, glass shards and grease collect in the filter at the tub floor, and the same sludge can block the hose or the disposal port it empties into. Less often the drain pump is jammed, or the sink drain downstream is blocked.

A quick way to separate the causes is to run the kitchen sink. If the sink also drains slowly or gurgles, the clog is shared and sits in the sink line. If the sink is fine and only the dishwasher holds water, the problem is within the machine or its short hose.

What should you check inside the dishwasher first?

Start with the filter and the sump. Remove the lower rack, twist out the cylindrical or flat filter, rinse it under warm water, and look into the sump for a broken glass shard, a bone or a label. Clear what you find, put the filter back, and run a short rinse cycle to test.

Steps:

1. Cut power and scoop out water.
2. Lift out the lower rack and the filter, then scrub both with a soft brush and dish soap.
3. Look under the filter for debris in the sump. Wear gloves, since broken glass is common.
4. Check the spray arm for blocked holes. A toothpick clears them.
5. Replace the parts and run a rinse cycle.

When the level never drops and the machine is silent at the end of a cycle, suspect a jammed or dead drain pump. That repair is a part swap, and many owners hand it to a technician.

How do you clear the drain hose and the sink connection?

Open the lower access panel or slide the machine out and locate the drain hose, the ribbed line that carries wash water from the pump over to the sink side. Disconnect it over a bucket, shake or rinse it out, and check for kinks. A hose that sags below the connection can hold water, so it should rise in a loop before it drops.

Called a high loop, it is strapped up under the counter so sink water cannot run back into the machine. Some installations use an air gap, a small fitting on the sink deck that does the same job. If you see a cap or fitting on the sink with the dishwasher line attached, unscrew its cap and clean it; air gaps clog with grime and cause backups.

On a sink with a disposal, check the inlet where the hose connects. A new disposal has a plug in this port that must be knocked out for the dishwasher to drain, and forgetting it is a classic reason a dishwasher will not drain after a fresh install. If you installed a disposal recently, look here first. The disposal installation guide explains the connection.

What if the sink drain itself is clogged?

Should the kitchen sink back up as well, the clog lies beyond the trap, and the dishwasher only shows it. Work with a plunger, then a hand auger, or take the trap apart and clean it. Deal with a disposal before anything else.

Safe tools: a cup plunger, a drain snake, and a bucket under the trap. Skip chemical drain cleaners. They sit in the standing water and can damage a dishwasher's seals, hoses and pump, and they are a hazard to anyone who later opens the pipe. A mix of hot water, baking soda and vinegar is a mild option for light grease, not for a solid blockage.

Related pages: clearing a kitchen sink, home remedies for a clogged sink drain, and unclogging a disposal drain. The cause behind recurring slow sinks is covered in why a sink drains slowly.

When do you need a plumber instead of a wrench?

Book help whenever more than one fixture backs up, if water rises in another sink or the laundry drain, if sewage smells appear, or if filter, hose and trap are all clean and water still sits. Each of those suggests a deeper line blockage that wants a cable or a camera.

Bob Vila's national guide lists clearing a clog at $150 to $350, and the written quote sets the price for your drain. The sink clog cost guide has the breakdown. A plain clog stays far below the $1,000 point where California begins requiring a contractor license, though larger repairs can pass it. A visit can be set up through the quote page.

In older Westside houses, a kitchen line is often cast iron or galvanized steel and may have a rough interior that catches grease. If the same clog returns every few months, ask the plumber about a camera look instead of repeating the same fix.

How can you stop the dishwasher from clogging again?

Scrape plates before loading, but do not rinse them clean, since modern detergents need some soil to work. Clean the filter monthly, run hot water at the sink before a cycle, keep grease out of the drain, and run a descaling cycle with a dishwasher-safe cleaner when you see buildup.

Hard water leaves scale in the pump and the hose. The City of Santa Monica's 2022 water quality report lists average hardness of 161 ppm for water the city delivers, so periodic cleaning is worthwhile. Do not pour fat down the sink, since it hardens in the trap and blocks flow back to the dishwasher.

Common questions

How long is the job?

Allow 20 to 40 minutes for filter and hose. A blocked sink line may add up to an hour. A pump swap or a cable run takes longer, and the plumber should name a window once the blocked section is known.

Will a bottle of drain opener help?

No. Those products are not made for dishwashers, harm rubber seals and hoses, and pool in the tub where they can splash. Clean the filter, inspect the hose, empty the trap and use a plunger or snake on the sink line instead.

What causes a smell once the water finally leaves?

Old food in the filter, trapped water in a sagging hose or a dirty air gap are the usual sources. Clean the filter, confirm the hose has its loop, and clean the air gap or disposal inlet. If a sewer smell comes from the sink, see the page on sewer smell.

Is this a plumbing call or an appliance repair?

A plumber suits clogs in the sink line, the disposal connection or the trap. An appliance technician suits a failed drain pump or a control fault. If the filter, hose and sink line are clear and the pump does not run, the machine is the likely problem.