Dishwasher Not Draining? 7 Causes and How to Fix Each One

Standing water in your dishwasher after a cycle is one of the most common appliance problems — and usually one of the easiest to fix. About 70% of dishwasher drainage issues are caused by a clogged filter or food trap, which takes 5 minutes to clean with no tools. Before you call a repair tech or start shopping for a new dishwasher, work through the 7 causes below in order. Most homeowners can fix this themselves in under 30 minutes.

How a Dishwasher Drains (Why This Matters)

Understanding the drain path helps you diagnose the problem faster. Water exits your dishwasher through a sequence: the tub drains through a filter screen (catches food particles), then a drain pump pushes the water out through a drain hose that connects to either your garbage disposal or the sink drain tailpiece. Many installations also include an air gap (a small device on your countertop) or a high loop (the hose loops up under the counter) to prevent dirty water from siphoning back into the dishwasher.

A blockage or failure at any point in this chain will cause water to pool in the bottom of the tub. The good news is that most blockages happen at the filter — the first and most accessible point.

7 Causes of a Dishwasher Not Draining (Most to Least Common)

1. Clogged filter or food trap (most common — fixes ~70% of cases). Every modern dishwasher has a removable filter at the bottom of the tub, usually in the center or back corner. It catches food particles, grease, broken glass, label paper, and other debris during the wash cycle. When this filter gets clogged, water can't pass through to the drain pump.

How to fix it: Remove the bottom dish rack. Look for a cylindrical filter assembly — it usually twists counterclockwise to unlock and lifts straight out. Some models have a coarse filter (outer mesh) and a fine filter (inner cylinder); remove both. Rinse under hot running water, scrubbing with a soft brush or old toothbrush to remove grease and stuck-on food. Check the sump area (the cavity where the filter sits) for debris like broken glass, bones, or small objects that may have fallen through the racks. Reinstall the filter, making sure it locks into place, and run a short rinse cycle to test.

2. Garbage disposal connection blocked. If your dishwasher drains into a garbage disposal, a full or clogged disposal will back water up into the dishwasher. This is the second most common cause and is often overlooked because the problem isn't in the dishwasher at all.

How to fix it: Run your garbage disposal with cold water flowing for 15–20 seconds to clear it. If you recently installed a new garbage disposal, check that the knockout plug was removed from the dishwasher drain inlet on the disposal. This is a very common installation mistake — the plug is a plastic disc inside the disposal's dishwasher inlet that must be knocked out with a screwdriver and hammer before connecting the drain hose. If it's still in place, no water can drain from the dishwasher.

3. Clogged or dirty air gap. The air gap is a small chrome or plastic dome on your countertop (usually next to the faucet or soap dispenser). It prevents dirty sink water from flowing backward into the dishwasher. Over time, food debris accumulates inside and restricts drainage.

How to fix it: Twist or pop off the decorative cap, then remove the inner cover. Clean out any visible debris — food particles, grease, or mineral buildup. Use a bottle brush or pipe cleaner to clear the tubes. Replace the cap and test with a short cycle. If you don't have an air gap, your installation should use a high loop — the drain hose should be secured as high as possible under the countertop before dropping down to the disposal or drain. If the hose isn't looped up, water can siphon back into the dishwasher.

4. Kinked or blocked drain hose. The drain hose runs from the dishwasher to the disposal or sink drain. It can get kinked when the dishwasher is pushed back into its cabinet space, or it can develop a clog from grease and food buildup over time.

How to fix it: Pull the dishwasher forward slightly (most slide on rails — you may need to remove two screws from the mounting brackets under the counter lip). Inspect the entire length of the drain hose for kinks, pinches, or visible blockages. A kinked section can usually be straightened by hand. If you suspect an internal clog, disconnect the hose from the disposal or drain tailpiece (have a towel and bowl ready — water will drain out) and flush it with hot water. If grease is the issue, run hot water mixed with a tablespoon of dish soap through the hose.

5. Drain pump failure. The drain pump is a small motor-driven pump that pushes water out through the drain hose. If it fails, you'll typically hear one of two things during the drain cycle: either complete silence (the pump isn't activating at all) or a humming/buzzing sound without any water movement (the motor is running but the impeller is stuck or broken).

How to fix it: This is where the DIY line starts to blur. First, check if something is jammed in the pump — small pieces of broken glass or food debris can block the impeller. With the dishwasher off and the filter removed, look into the sump area for the pump access. On some models you can reach the impeller and clear debris manually. If the pump motor itself has failed (no sound at all during drain, or the impeller spins freely but no water moves), the pump needs to be replaced. A replacement drain pump costs $40–$120 in parts depending on the brand. If you're handy, it's a 30–60 minute job; otherwise, this is where a pro makes sense.

6. Drain solenoid or check valve issue. Some dishwashers use a drain solenoid (an electromagnetic valve) to open the drain path when the pump runs. If the solenoid fails, the valve stays closed and water can't exit even though the pump is running normally. Similarly, a stuck check valve (a one-way flap that prevents backflow) can block drainage.

How to fix it: This requires accessing the underside of the dishwasher, which means pulling it out from the cabinet. The solenoid is typically located near the drain pump. You can test it with a multimeter for continuity — if it doesn't have continuity, it needs to be replaced ($15–$40 part). Check valves can sometimes be cleaned and freed manually. If you're not comfortable with electrical testing, call a pro.

7. Drain timer or control board malfunction. If the dishwasher runs through the wash cycle normally but never initiates the drain cycle at all, the issue may be electronic — a failed drain timer, a faulty control board, or a wiring problem. This is the least common cause but the most expensive to repair.

How to fix it: Check if your dishwasher is displaying an error code — consult your owner's manual or search the code online to see if it points to a drain-related fault. Some models let you force a drain cycle by pressing and holding a specific button combination (check your manual). If the control board has failed, replacement costs $100–$300 for the part. At that price point, compare the repair cost to the age and value of the dishwasher — if it's more than 8–10 years old, replacement may make more sense.

Still Not Draining? Troubleshooting by Symptom

If you've worked through the 7 causes and the dishwasher still isn't draining, match your specific symptom to narrow down the problem:

Water pools after every cycle but the dishwasher seems to run normally. The filter is the most likely cause, even if it looks clean. Food grease can coat the mesh and reduce flow without looking obviously clogged. Soak the filter in hot water with a tablespoon of dish soap for 10 minutes, then scrub with a brush and rinse. Also check whether the drain hose has a low spot (sag) where water sits instead of flowing downhill to the disposal.

Dishwasher not draining completely — leaves some water but not a full pool. A small amount of water at the very bottom of the tub (below the filter level) is actually normal on most models — it keeps the pump seal lubricated. But if water is covering the filter or pooling more than half an inch, you likely have a partial blockage in the filter, air gap, or drain hose. A partially kinked hose is a common culprit — it allows some water through but restricts full flow.

Dishwasher not draining but there's no visible blockage anywhere. If the filter is clean, the hose has no kinks, and the disposal is clear, check the air gap or high loop — a clogged air gap is often invisible from the outside. If all drain path components are clear, the issue is likely the drain pump or drain solenoid. Listen during the drain cycle: silence means the pump isn't activating; humming without water movement means the pump is stuck or the solenoid/check valve is blocking flow.

Sink and dishwasher both not draining. If both your kitchen sink and dishwasher won't drain, the shared drain line is blocked downstream of where they connect. This is a plumbing issue, not a dishwasher issue. Try plunging the sink or using a drain snake. If that doesn't clear it, you need a plumber.

Brand-new dishwasher not draining on first use. Almost always the garbage disposal knockout plug — installers sometimes forget to remove it. Pull the drain hose from the disposal inlet and check for the plastic plug. If you don't have a disposal, verify the drain hose is connected to the correct inlet on the sink tailpiece and that there's no cap or plug blocking it.