What to Do When Your Dishwasher Won't Drain

Finding a pool of murky, stagnant water at the bottom of your dishwasher after a cycle is a frustrating discovery. Not only is it unsanitary, but it also means your dishes are far from clean. The good news is that a dishwasher that won't drain is a common household problem, and you can often fix it yourself with a few simple troubleshooting steps.

This guide will walk you through the most frequent causes of a clogged dishwasher and how to resolve them safely. We'll also help you identify when the issue requires a professional touch.

Safety First: Turn Off the Power

Before you begin any inspection or repair work, your top priority is safety. Water and electricity are a dangerous combination. To avoid any risk of electric shock, you must disconnect the dishwasher from its power source.

You can do this by either unplugging the unit from the wall outlet, which is often located under the sink, or by switching off the dedicated circuit breaker for the dishwasher in your home's electrical panel. Once the power is off, you can safely proceed with your investigation.

Common Causes for a Dishwasher Not Draining

Most drainage issues stem from a simple blockage. By checking a few key areas, you can usually locate and clear the obstruction without needing special tools.

1. Check for a Clogged Filter

Your dishwasher's filter is designed to catch food particles, debris, and other small objects to prevent them from clogging the drain system. Over time, this filter can become blocked, stopping water from draining properly.

• Locate the Filter: The filter is typically a cylindrical component found on the floor of the dishwasher, usually beneath the lower spray arm. You may need to remove the bottom rack to access it.
• Remove and Clean: Most filters can be removed by twisting them counter-clockwise. Once removed, take it to the sink and wash it thoroughly with warm, soapy water. Use a soft brush to gently scrub away any stubborn food residue.
• Inspect the Sump: With the filter removed, check the area underneath it (the sump) for any larger pieces of debris that might be causing a blockage.
• Reinstall: Once clean, securely place the filter back into its housing. Running the dishwasher without the filter can lead to more serious damage to the pump and drain lines.

After cleaning the filter, run a short rinse cycle to see if the problem is resolved.

2. Inspect the Drain Hose

The drain hose is a flexible, ribbed tube that carries wastewater from your dishwasher to the garbage disposal or the main drain pipe under your sink. Kinks or clogs in this hose are another frequent reason for drainage failure.

• Look for Kinks: Visually inspect the entire length of the hose that runs from the dishwasher to the sink's plumbing. Ensure it isn't bent, twisted, or pinched behind the appliance or under the sink. Straightening out a kink is often all it takes to fix the issue.
• Check for Clogs: If there are no visible kinks, the hose itself may be clogged. Place a bucket or pan under the connection point at the sink, and disconnect the hose. Allow any trapped water to drain into the bucket.
• Clear the Hose: Carefully inspect both ends of the hose for blockages. You can try to dislodge any clogs by gently blowing through the hose or by using a plumber's snake to clear the obstruction. Once clear, reattach it securely.

3. Clear the Garbage Disposal

Many dishwashers drain directly into the garbage disposal. If the disposal is clogged with food waste, it will prevent water from the dishwasher from draining away.

• Run the Disposal: Before starting a dishwasher cycle, always run your garbage disposal with cold water for about 30 seconds to ensure it's clear.
• Check the Knockout Plug: If your dishwasher is newly installed, the installer may have forgotten to remove the knockout plug inside the disposal's dishwasher connection nipple. To check this, you'll need to disconnect the drain hose from the disposal and feel inside the nipple for a plastic plug. If it's there, carefully knock it out with a screwdriver and hammer, then retrieve the plastic piece from the disposal.

4. Examine the Air Gap

Some plumbing codes require an air gap, which is a small cylinder-shaped fixture located on your countertop near the sink. Its purpose is to prevent contaminated drain water from siphoning back into your dishwasher. Like other components, it can get clogged.

• Remove the Cover: Pull off the metal or plastic cover of the air gap.
• Clean Inside: Underneath, you'll see a smaller plastic cap. Remove it and clean out any food particles or grime that have built up inside. A small brush or pipe cleaner can be very effective.
• Test the Drain: Once clean, reassemble the air gap and run a rinse cycle on your dishwasher.

When to Call a Professional Plumber

While these DIY steps can solve many drainage problems, some issues are more complex and require professional expertise. You should consider calling a plumber if:

• You've tried all the troubleshooting steps above and the dishwasher still won't drain.
• You suspect the problem lies with the dishwasher's drain pump or motor, which are more difficult and risky to repair.
• The issue appears to be related to your home's main plumbing lines rather than just the dishwasher.
• You are not comfortable performing any of the inspection or cleaning steps yourself.

Attempting complex repairs without the proper knowledge can lead to further damage to your appliance or even cause water damage to your kitchen.

Get Expert Help from A Rescue Rooter

Don't let a clogged dishwasher disrupt your routine. If you're facing a stubborn drainage issue or prefer to leave the work to an expert, the team at A Rescue Rooter is here to help. Our professional plumbers have the tools and experience to quickly diagnose and resolve any plumbing problem, from a simple clog to a complex repair. We ensure the job is done right, so you can get back to enjoying the convenience of a fully functional dishwasher.