You open the dishwasher and there’s a pool of dirty water sitting in the bottom. Annoying, but rarely serious — a dishwasher that won’t drain is almost always a clog somewhere between the tub and your sink drain, and most of those you can clear yourself in 20 minutes. Here’s the order I check things in.
First: bail out the standing water
You can’t work on it full of water. Scoop out what you can with a cup, then soak up the rest with towels. Lay a towel under the unit too — you’ll be disconnecting a hose later and a little spillover is normal.
Find the clog, in order of likelihood
| Check | Why it’s the culprit |
|---|---|
| Garbage disposal knockout plug | If you just installed a new disposal, the drain plug may never have been knocked out — the #1 cause of a brand-new dishwasher not draining |
| The dishwasher filter | Food and grease clog the basket at the bottom of the tub |
| The drain hose | Kinked or clogged where it loops up under the sink |
| The air gap | That little cylinder on the sink can clog and back water up |
| The sink drain itself | A clogged kitchen drain has nowhere to send the dishwasher’s water |
The garbage disposal connection (check this first if it’s new)
Your dishwasher almost always drains through the garbage disposal. Two things to know: if you recently replaced the disposal, the factory knockout plug in its dishwasher inlet must be punched out — forget that and the dishwasher can never drain. And if the disposal is full or jammed, the dishwasher backs up too, so run the disposal and confirm it works. My guide on a garbage disposal that’s not working covers clearing a jam.
Clean the filter
Most modern dishwashers have a removable filter at the bottom, under the lower spray arm — twist and lift it out. It’s usually packed with food sludge, glass grit, and grease. Rinse it under hot water with a brush and drop it back in. People go years without cleaning this, and it’s a common, easy fix.
Check the drain hose and air gap
Under the sink, find the corrugated drain hose running from the dishwasher to the disposal or drain. Make sure it isn’t kinked, and feel for a soft clog. If your sink has an air gap (a small chrome cylinder on top of the sink), pop the cap and clear any gunk — a clogged air gap will back water right into the tub.
Still backing up? It’s the sink drain
If the dishwasher’s drain path is clear but water still won’t go, the problem is the kitchen sink drain it empties into. Run the sink — if it’s slow too, you’ve found it. My guide on how to unclog a drain walks through clearing it, and a drain snake handles the stubborn ones. Skip harsh chemical drain cleaners here — they can sit in the dishwasher line and damage seals.
Frequently asked questions
Why is there standing water in the bottom of my dishwasher? The drain path is blocked. The usual suspects are a clogged filter, a kinked or clogged drain hose, a jammed garbage disposal, or a clogged kitchen sink drain. A small amount of water in the sump is normal; a full pool is a clog.
Why won’t my new dishwasher drain? Most often the garbage disposal’s knockout plug was never removed during install. The dishwasher drains into the disposal, and that plug blocks the connection until it’s punched out.
Can I use Drano in my dishwasher? No. Chemical drain cleaners can damage the dishwasher’s pump seals and hoses and may sit in the line. Clean the filter and clear the hose mechanically, or snake the sink drain instead.
Will baking soda and vinegar fix a dishwasher that won’t drain? It can freshen the tub but won’t clear a real clog. You need to physically clean the filter and check the hose, disposal, and sink drain.
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