Dishwasher Not Draining: Causes and When to Call a Plumber

A dishwasher that will not drain leaves standing water at the bottom of the tub after the cycle finishes. It is a common problem, and in many cases the fix is something you can do yourself in under fifteen minutes. Here is how to work through it.

Check the Filter First

Most modern dishwashers have a cylindrical filter at the bottom of the tub that catches food debris. When this filter gets clogged, water cannot drain properly. It is the most common cause of standing water and the easiest fix.

To clean it: remove the bottom rack, twist the filter counterclockwise and lift it out (the exact mechanism varies by brand - check your manual), rinse it under warm running water, and use a soft brush to clear any debris. Reinstall and run a short cycle to see if drainage improves.

Check the Drain Hose

The drain hose runs from the dishwasher to either the garbage disposal or the drain beneath the kitchen sink. If the hose is kinked, clogged, or installed incorrectly, water will not drain.

Pull the dishwasher out slightly (or open the cabinet under the sink) and trace the drain hose. Look for kinks - straighten any you find. If the hose connects to the garbage disposal, make sure the knockout plug was removed when the disposal was installed. This is a common oversight when a new disposal is added - a plastic plug inside the disposal inlet blocks the dishwasher drain completely. Remove the disposal knockout plug if present.

Also check that the drain hose runs up high before dropping down to the connection point (called a high loop). Without this, water can back-siphon from the sink into the dishwasher.

Check the Garbage Disposal Connection

If your dishwasher drains into the garbage disposal, run the disposal before starting a dishwasher cycle. A clogged disposal prevents the dishwasher from draining. If the disposal is clear and the dishwasher still will not drain, disconnect the hose at the disposal connection and check for blockage in the hose itself.

Check the Air Gap (If Present)

Some kitchens have an air gap - a small chrome or plastic cap on the countertop or sink deck near the faucet. The air gap prevents drain water from back-flowing into the dishwasher. It can become clogged with debris. Remove the cap and clean out any buildup inside.

Run a Drain Cycle Manually

Many dishwashers allow you to force a drain cycle. Cancel the current cycle and press Start again - this often triggers a drain at the beginning of the cycle. Some brands have a specific drain-only cycle option.

When the Problem Is Not DIY

Call a plumber if the drain hose and filter are clear but water still sits at the bottom, water is backing up into the sink when the dishwasher drains, the drain pump is making noise but water is not moving, or there is a gurgling sound from the sink drain when the dishwasher runs.

Sources and editorial notes

Prices and permit requirements vary by location, property, equipment, and scope. Treat price ranges as planning estimates and confirm current requirements with the relevant authority and contractor.

• US Small Business Administration - business guide

Related guides

• Dishwasher Installation Requirements: Plumbing, Power, and Space
• Appliance Installation Cost Guide (Dishwasher, Range, Washer)
• Water Heater Leaking from the Bottom: Shutoff and Damage-Control Guide

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