Short answer: standing water in the bottom of your dishwasher is almost always a blockage, not a broken machine — a clogged filter, a garbage-disposal knockout plug left in after installation, a blocked air gap, or a kinked drain hose cause most of the no-drain calls we run. The pump itself is the last thing we suspect, and it's the order below that gets you there.
A dishwasher that won't drain is one of the most satisfying problems in this trade, because the fix is usually free and sits within arm's reach. Before you start, do two things: cancel the cycle (most machines attempt a drain when you do — listen for the hum), and bail or shop-vac the standing water so you can see the bottom of the tub. Then work through these checks in the order we'd check them on a service call.
Is the filter or sump clogged?
This is where we start every time. At the bottom of the tub, under the lower spray arm, there's a twist-lock cylindrical filter sitting in the sump — the low point where all the wash water collects before the pump pushes it out. Twist the filter out, rinse it under the tap, and then look (and carefully feel) into the sump opening it came from. Broken glass, fruit-pit fragments, toothpicks, and pasta sludge collect right there, sitting directly on top of the drain pump inlet.
If the filter was packed solid, you've likely found your problem — and your dishes were probably coming out gritty too, since a clogged filter is also the top cause of a dishwasher not cleaning. Reseat the filter, run a rinse cycle, and watch whether the water leaves.
Did the disposal's knockout plug ever get removed?
If the dishwasher stopped draining right after a garbage disposal was installed — or the dishwasher itself is the new arrival — stop and check this before anything else. Garbage disposals ship with a solid knockout plug inside the dishwasher inlet port. The installer is supposed to punch it out before connecting the dishwasher drain hose. When it's left in place, the dishwasher pumps against a sealed wall and the water comes right back.
The fix: disconnect the drain hose at the disposal, and if you can feel or see a solid plug inside the inlet nipple, tap it into the disposal chamber with a screwdriver and hammer, fish out the plastic disc, and reconnect. This one embarrasses a lot of installers, and we find it more often than you'd think.
Even with the plug out, a disposal packed with food scraps blocks the same path. Run the disposal until it's clear before every dishwasher cycle — it shares the drain.
Is the air gap or high loop clogged?
Look at your sink. If there's a small chrome or plastic cylinder on the counter near the faucet, that's an air gap — a backflow-prevention fitting the dishwasher drains through. If water spits out of it during the drain cycle, or it gurgles and the tub won't empty, the air gap is clogged. Pop the cap off (usually a twist or pull), clear the debris inside, and check the short hose from the air gap down to the disposal — that stub of hose is a classic clog point.
No air gap on the counter? Then your drain hose should rise in a high loop fastened up under the countertop before dropping to the drain. A hose that sags low along the cabinet floor lets dirty sink water flow backward into the tub — which looks exactly like a drain problem, except the water shows up between cycles.
Is the drain hose kinked or clogged?
The corrugated drain hose runs from the dishwasher, through the cabinet sidewall, to the disposal or sink drain. Two failure modes:
- Kinks. If the dishwasher was recently pushed back into its alcove or anything heavy got shoved under the sink, the hose can fold flat. Look under the sink first, then behind the kick panel.
- Internal clogs. Years of grease and food sludge narrow the hose, especially at the corrugations and at the connection fittings. Disconnect it at the disposal end (towels down, clamp pliers or a screwdriver for the clamp) and check whether water flows through. Blowing through it or running a flexible brush tells you quickly whether it's open.
A clogged hose is a DIY fix if you're comfortable under the sink; replacing one that's hardened and cracked is cheap insurance while you're in there.
Has the drain pump failed?
If the filter is clean, the disposal path is open, the air gap is clear, and the hose flows freely — now we suspect the pump. Two ways it fails:
- Jammed: a shard of glass or a fruit pit gets past the filter and locks the impeller. The pump hums or buzzes but doesn't move water. Sometimes you can see and remove the debris through the sump; sometimes the pump has to come out.
- Dead: the motor winding fails and the pump is silent during the drain portion of the cycle. That's a replacement.
Pump replacement means pulling the dishwasher, tipping it, and working at the base near the wiring — this is the point where we'd tell a friend to put the screwdriver down and book dishwasher repair. It's a routine job for a tech and one of the most common dishwasher parts we replace.
Is the check valve letting water back in?
One more pattern worth knowing: the dishwasher drains fine, but an inch of water reappears in the tub hours later. That's usually the check valve — a one-way flap between the pump and the drain hose that's supposed to stop expelled water from flowing back. When it wears or sticks open, water in the hose (or backwash from the disposal) drifts back into the sump. A failed check valve, a low-sagging drain hose with no high loop, and a clogged disposal all produce this same "it comes back" complaint, which is why we check all three together.
What's DIY-safe and what's a service call?
| Check | DIY-safe? | Why |
|---|---|---|
| Filter and sump cleaning | ✅ Yes | Hand tools only, top of the tub |
| Disposal knockout plug | ✅ Yes | Screwdriver job under the sink |
| Air gap / high loop | ✅ Yes | Visible at the countertop |
| Drain hose kink or clog | ✅ Mostly | Under-sink access; mind the clamps |
| Drain pump replacement | ❌ Call | Pulling the unit, base-level wiring near water |
| Check valve replacement | ❌ Call | Same access as the pump |
| Repeat clogs with no found cause | ❌ Call | Could be the house drain line, not the dishwasher |
One safety note that applies to every step past the filter: kill power to the dishwasher at the breaker before reaching into the sump or disconnecting hoses, and never put your hand into a garbage disposal — work its inlet from the outside.
When it isn't the dishwasher at all
If the kitchen sink itself drains slowly or gurgles when the dishwasher runs, the blockage may be in the house drain line downstream of both — no dishwasher part will fix that. The tell: water backs up into the sink during the dishwasher's drain cycle. That's a plumbing call, not an appliance call, and it's worth ruling out before paying for either. (Front-load washing machines have an almost identical drain story, which we cover in washer not draining.)
What a dishwasher drain repair costs
If the blockage checks above don't solve it, you're most likely into a drain pump or check valve. Dishwasher repairs run $100–$300 depending on the part, and every job starts with a $75 service call that's applied toward the repair. You get a written quote after diagnosis, before any work begins — and a 90-day parts-and-labor warranty after it. If your machine is past its expected life, our repair vs. replace guide helps you make that call with the quote in hand.
Frequently Asked Questions
Why is there standing water in the bottom of my dishwasher?
The most common cause we find is a clogged filter or sump at the bottom of the tub — food debris blocks the path to the drain pump. After that come a kinked or clogged drain hose, a blocked air gap, and, on new installs, a garbage-disposal knockout plug that was never removed.
How do I force my dishwasher to drain?
Most dishwashers run a drain-only sequence when you cancel a cycle — press and hold Cancel or Start/Reset for about three seconds and listen for the pump. If water still won't leave, scoop or shop-vac it out, then clean the filter and check the drain hose before trying again.
Can a garbage disposal cause a dishwasher not to drain?
Yes, two ways. If the disposal was just installed, the knockout plug inside its dishwasher inlet may never have been punched out — the water has nowhere to go. And a disposal packed with food scraps blocks the same drain path. Run the disposal before each dishwasher cycle.
How much does it cost to fix a dishwasher that won't drain?
If it's the drain pump or check valve, dishwasher repairs typically run $100–$300 including parts and labor. Every job starts with a $75 service call applied toward the repair, with a written quote after diagnosis and a 90-day parts-and-labor warranty. Clogs you clear yourself cost nothing.
Dishwasher still not working?
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In Pittsburgh? See Dishwasher Repair in Pittsburgh.