You open the dishwasher after a cycle and there's an inch of water in the bottom. Not a flood, not a leak — just water that should have left and didn't. Before you call anyone, there are five likely causes, and four of them are fixable in under an hour with a $5 part or no part at all.
This guide walks through them in order from cheapest to most expensive to diagnose. Start at the top and work down. If you get to the last one, the next step is a service call.
First, the obvious: is the disposal full?
About a third of dishwasher-not-draining cases aren't really dishwasher problems. The dishwasher drains into the garbage disposal on most installations, and if the disposal is clogged — old food, a piece of bone, a wrapper that slipped past — the dishwasher has nowhere to send its water.
Check this first because it costs nothing. Run the disposal for 10-15 seconds. Run hot water through it. Then run the dishwasher on a rinse-only cycle and see if it drains.
There's a related issue worth checking the same day: if you have a new install or recently replaced your disposal, look for the small plastic plug at the dishwasher's drain inlet on the disposal. New disposals ship with that plug installed because they're designed to also serve sinks without dishwashers. If your installer forgot to knock it out, your dishwasher has been trying to drain into a sealed port. This is more common than you'd think.
Second: the filter
Most modern dishwashers — anything made after roughly 2010 — have a user-cleanable filter at the bottom of the tub. Some manufacturers tell you about it in the manual; many don't tell you well, and most homeowners never clean it.
Pull the lower rack out. Look at the bottom of the tub. You'll see a cylindrical or two-piece filter assembly, usually with a small handle or tab to twist. Twist counterclockwise to unlock it (in most models — check yours), lift it out, and look at what comes with it. If it looks like a small science experiment, you've found a contributing problem.
Rinse it under hot water. A soft brush helps. Don't use anything sharp; the filter mesh is fine and tears easily. Reinstall it, lock it in place, and run a cycle.
A choked filter doesn't always cause a complete drain failure, but it slows drainage and contributes to standing water. Cleaning it monthly is the maintenance the manual probably told you about and you definitely didn't do.
Third: the drain hose
If the disposal is clear and the filter is clean and you still have standing water, the next likely culprit is the drain hose — the corrugated rubber line that runs from the dishwasher pump to either the disposal or an air gap on the counter.
The hose has two common failure modes. The first is a kink. Pull the dishwasher forward a few inches (don't force it; on most installations it slides out if you remove the screws holding it to the underside of the counter) and look at the path of the hose. It should rise to its highest point — either an air gap on the counter or a "high loop" zip-tied to the underside of the counter — before descending to the disposal. If it's kinked or the high loop has slumped, straighten it.
The second failure mode is a clog inside the hose. Disconnect the hose at the disposal end (a hose clamp, one screw), put the end in a bucket, and pour a quart of water through it from the dishwasher end. If the water won't pass, you have a clog. The fix is usually either flexing the hose until the clog breaks up, or replacing the hose entirely. Generic dishwasher drain hose runs $10-20 at any hardware store; brand-specific replacements are $15-40. Universal hose works for almost all installations.
Fourth: the air gap (if you have one)
In a few states — California most prominently — code requires an air gap on the counter for dishwasher installations. It's the small chrome cylinder near the faucet with vents in it. The air gap prevents dirty disposal water from siphoning back into the dishwasher.
Air gaps clog. The fix is to unscrew the top cap, pull off the inner cover, and check the inlet for debris. A toothbrush usually clears it. If you can blow through the air gap with no resistance, it's clean.
If you don't have an air gap (most installations outside California don't), skip this step.
Fifth: the drain pump
If all of the above are clear and you still have standing water, the drain pump itself has likely failed. This is the only one of the five where the part costs more than $30 and the diagnosis requires partially disassembling the dishwasher.
The drain pump is a small electric pump mounted under the dishwasher, usually accessible from inside the tub once you remove the filter assembly and pull out the lower spray arm. On most models, you'll see a small impeller. If it spins freely and you can hear no humming when the drain cycle is supposed to run, the motor is gone. If it hums but won't spin, something is jammed in the impeller — usually a piece of glass, a fruit pit, or a label that came off a jar.
Replacement drain pumps run $25-90 depending on brand and model. The actual replacement is about a 30-minute job for a careful DIY-er with a model-specific YouTube guide. If you're not comfortable disconnecting the wiring harness and the discharge hose, this is the point where service-call math starts to make sense. A service visit runs $100-200; the part is half that. The breakeven depends on whether you're confident.
How to find your model and the right part
The single most useful thing you can do before ordering a replacement pump or hose is find your dishwasher's exact model number, not just the brand. Manufacturers make dozens of dishwasher models with similar names and incompatible parts.
The model number is on a sticker, usually inside the door frame on the left or right side. Open the door, look at the metal frame around the tub opening. The sticker has the model number (often starts with letters then a long alphanumeric string) and a serial number. Take a photo of it before you order anything. (Full per-appliance plate-location guide: where to find the model number on every major appliance.)
Once you have the model number, parts sites like RepairClinic, Sears Parts Direct, or AppliancePartsPros all let you search by model number and show you the exact pump or hose your unit takes. The price difference between brand parts and equivalent third-party parts is usually $10-30; both are fine for a part you're not going to think about for another decade.
When to give up and call
If you've worked through all five and the water is still there, the most likely remaining issues are a control board failure or an issue with the dishwasher's water inlet (water coming in faster than it can leave). Both of those are service-call territory. Most experienced appliance techs will diagnose in 15-30 minutes and tell you whether the repair is worth the part cost relative to a new dishwasher.
The rough rule: if the dishwasher is over ten years old and the repair quote is over $200, replacement starts to make sense. Under ten years and under $200, repair almost always wins on lifecycle cost. Before you call, look up whether your dishwasher is still under warranty — the answer is often yes even when you can't find the paperwork.
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