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Dishwasher Not Draining: Causes and Fixes in Order

Kitchen guide · Decoded from manufacturer documentation · Safe homeowner checks only

Why this happens

A dishwasher empties itself through one of the shortest plumbing paths in the house, and every inch of it is a narrowing where food can settle. The cycle's dirty water collects in the sump, the well in the tub floor, and passes through the filter screens that guard the drain pump. The pump then pushes it out through the drain hose, usually rising first to an air gap fitting on the counter or a high loop under it, and finally into a garbage disposal inlet or a sink drain tailpiece. Standing water at the end of a cycle means that path accepted the water at wash speed and refused it at drain speed, or that the push behind it has weakened. The filters are the usual refusal: they are designed to catch food, and they keep catching it until the layer mats into felt and the pump is drinking through fabric. The air gap is the second narrowing, a fitting whose entire job is to hold an open break in the line so drain water can never siphon back, and whose cap quietly fills with sludge. The disposal inlet and the hose's low loop collect their share after that. Only at the end of the list does the pump itself wear out, usually after years of straining against the very blockages listed above it, which is why the order of work on this page is also the order of likelihood.

Finding the cause

Start with a drain command and your ears

Cancel the cycle and invoke the drain function if your model offers one, then simply listen. A pump you can hear, running its normal length and sounding even, tells you the motor and its power supply live, and pushes the diagnosis towards the path. A pump that strains, rattles or stops early suggests debris at the impeller or a blockage close to home. Silence is the third answer, and it points at the pump or its supply before any clean out is worth doing. That single observation, noted honestly, decides the shape of everything after it.

Take the filters out and read them

Scoop out the standing water, remove the lower rack, and lift the filter set from the tub floor. A healthy filter rinses clean in seconds. A filter wearing a grey mat, or a sump well underneath it full of sludge, seeds, labels and bone fragments, is the classic finding on this fault and explains a drain that has slowed over weeks rather than stopping in a day. Wear gloves in the sump: broken glass collects there and hides in the residue.

Clear the air gap if your sink wears the chrome cap

In the many US installs whose plumbing code requires one, the drain hose routes up through the air gap beside the faucet, and the fitting clogs with food sludge exactly as a filter does, just out of sight. Pop the cap, remove the inner cover, and clear the sludge with a bottle brush. An air gap blocked enough to matter sometimes announces itself by weeping water onto the counter during the drain, which owners mistake for a faucet leak.

Give the disposal connection its moment

Sludge builds at the disposal inlet where the hose arrives, and running the disposal for thirty seconds with cold water clears its chamber. The special case deserves its reputation: on a brand new disposal, the factory knockout plug sealing the dishwasher inlet is sometimes never removed, and the dishwasher then has no drain path at all. A machine that stops draining on its first cycle after a disposal install is that plug until proven otherwise, every time.

Follow the hose for the low loop and the kink

The drain hose can kink behind the machine where it was pushed back, and it almost always has a low loop somewhere under the sink where grease and fine debris settle into a plug over years. Straighten what you can see, and treat a hose that has gone stiff, slimy inside or repeatedly blocked as a wear item rather than a mystery. Bosch and Samsung models use fine cylinder filters that clog visibly and early, while older Whirlpool and GE designs lean on a hard food disposer and a sump screen, so the emphasis shifts by brand but the path never changes.

Reading the results

Fixing it

1. Run the listening test, two minutes. Cancel, command a drain, and record the result honestly: even running, straining, or silent. This decides whether you are cleaning or repairing.
2. Wash the filter set and clear the sump, about fifteen minutes. Scoop out standing water first, wash the filters thoroughly, and pick the sump well clean of glass, labels, seeds and bone fragments, wearing gloves.
3. Check the pump cover area, about ten minutes. On models with a removable pump cover in the sump, lift it per the model's design and clear anything sitting at the impeller mouth.
4. Clear the air gap, about five minutes. Cap off, inner cover out, sludge brushed clear, and a jug of water poured through to prove the fitting is open.
5. Clear the disposal path, about ten minutes. Run the disposal with cold water, and on a new unit confirm the knockout plug is gone, with the disposal power off while the hose is disconnected.
6. Flush and prove it, one short cycle. Run a rinse or the shortest cycle empty, with a dishwasher cleaner or a cup of white vinegar on the top rack if you like, and watch the drain stage empty the tub in about a minute. Full emptying at normal speed is the fix confirmed.

Costs

All prices on this page are estimates based on typical US parts and service pricing. Your model, region and the actual failed part will move the real figure.

Repair or replace: clean outs are free at any age, and a fitted pump in this range is a rational repair on a dishwasher that cleans well and is not leaking elsewhere. A machine that needs a pump on top of rack, seal and control problems has crossed into replacement territory, and the drain fault is simply the first bill to arrive.

Mistakes that make it worse

• Running the cycle again to see if it clears itself. The wash fills from the dirty water sitting in the sump, redeposits grit on the dishes, and strains the pump against the same wall.
• Skipping the air gap because it sits outside the machine. It is inside the drain path in every way that matters, and it clogs on the same schedule as the filters.
• Probing the sump bare handed. Glass and bone in the sludge are effectively invisible, and the pump well is where they collect.
• Leaving the knockout plug disc inside a new disposal. The disc becomes a floating blockage that causes the next no drain story, sometimes months later.

Brand codes for this same fault live in the Dishwasher Error Codes hub, including the Bosch E24 guide.

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