Dishwasher Not Draining? 6 Causes & Fixes

Published: May 3, 2026 · By SAVA HVAC & Appliance Repair

Opening your dishwasher after a cycle to find an inch of murky water sitting at the bottom is frustrating — and it usually means the drain system has a blockage or a failed component. The good news is that several causes are DIY-fixable in under 10 minutes. Here are the six most common reasons a dishwasher won't drain, starting with the easiest to check.

1. Clogged Dishwasher Filter

Most modern dishwashers (Bosch, KitchenAid, Miele, Samsung, and others) use a manual filter rather than a self-cleaning grinder. That filter traps food debris during every wash — and if it hasn't been cleaned in months, it can become packed enough to block drainage entirely. This is the most common cause of standing water, and the easiest to fix.

How to clean it: Pull out the bottom rack. Locate the cylindrical filter at the bottom of the tub — usually near the center or back. Twist it counterclockwise to unlock it and lift it out. Rinse under running water and scrub with a soft brush (an old toothbrush works well) to remove grease and food buildup. Reinstall, run a short cycle, and check if water drains. Clean the filter every 1–3 months going forward.

2. Blocked or Kinked Drain Hose

The drain hose runs from the dishwasher pump to the sink drain or garbage disposal under your kitchen sink. Over time it can kink (especially if items were pushed against it under the sink), develop a blockage from grease accumulation, or come partially disconnected. A kinked hose is a complete blockage — even a well-functioning pump can't push water through it.

What to check: Open the cabinet under your sink and trace the corrugated drain hose from the dishwasher. Make sure it runs in a smooth loop without any sharp bends or tight kinks. Also check that the hose is connected firmly at both ends — the dishwasher connection and the disposal or sink drain. If it's kinked, straighten or reroute it. If it's blocked internally, it will need to be disconnected and cleared.

3. Garbage Disposal Knockout Plug

If your dishwasher stopped draining right after a new garbage disposal was installed, this is almost certainly the cause. New disposals ship with a plastic knockout plug inside the dishwasher drain inlet — the installer is supposed to knock it out when connecting the dishwasher drain hose. If they missed this step, the drain hose is completely blocked at the disposal connection.

Fix: Disconnect the drain hose from the disposal's side inlet. You'll see the plastic plug inside the inlet. Use a screwdriver and hammer to knock it into the disposal chamber, then fish it out (don't leave it in the disposal — it will damage the blades). Reconnect the hose and run a drain cycle.

4. Failed Drain Pump

The drain pump is the motor that forces water out of the dishwasher tub at the end of a cycle. If you've cleaned the filter, checked the hose, and confirmed the drain is clear but water still won't drain — or you hear a humming sound during the drain cycle with no water movement — the drain pump has likely failed. Drain pump failures are common after 7–10 years of use, or when a large piece of debris (broken glass, a pit from a fruit) gets past the filter and jams the impeller.

A drain pump replacement is a technician job — it requires pulling the dishwasher out and accessing the pump from underneath. Parts and labor typically run $150–$300 depending on brand and model.

5. Clogged Air Gap

Some kitchens have an air gap — a small chrome or plastic fitting mounted on the countertop or sink deck next to the faucet. It's a backflow prevention device for the dishwasher drain. When an air gap clogs with debris, water backs up into the dishwasher tub instead of draining to the disposal. If you have one of these fittings, remove the decorative cap, lift out the inner cap, and clear any debris you find inside.

6. Blocked Sink Drain or Garbage Disposal

Your dishwasher drains into the same plumbing as your sink. If your kitchen sink is draining slowly or not at all, the dishwasher has nowhere to push its water. Run the garbage disposal to clear any food buildup, and check whether the sink itself is draining normally. If the sink drain is partially blocked, clearing it will often restore dishwasher drainage without any other repair.

Quick Diagnosis Checklist

Frequently Asked Questions

Why is there standing water in my dishwasher after the cycle?

The most common causes are a clogged dishwasher filter, a blocked or kinked drain hose, or a garbage disposal knockout plug that was never removed. Start by cleaning the filter at the bottom of the dishwasher tub — this alone resolves most drainage problems.

How do I clean my dishwasher filter?

Remove the bottom rack and locate the cylindrical filter at the bottom of the tub. Twist it counterclockwise and lift it out. Rinse under running water and scrub with a soft brush to remove grease and debris. Reinstall and run a short cycle to test drainage. Most filters should be cleaned every 1–3 months.

Why did my dishwasher stop draining after I got a new garbage disposal?

New garbage disposals ship with a plastic knockout plug inside the dishwasher drain inlet. If the installer didn't remove it, your drain hose is completely blocked at the disposal. Disconnect the hose, knock out the plug with a screwdriver, retrieve it from inside the disposal, reconnect the hose, and test.

How much does it cost to fix a dishwasher that won't drain?

If the fix is a clogged filter or blocked drain hose, you may resolve it yourself at no cost. If the drain pump has failed, parts and labor typically run $150–$300 depending on brand and model. SAVA charges a $79 diagnostic fee credited toward the repair if you proceed.