How to Troubleshoot a Dishwasher That Won’t Drain

Having a dishwasher that won’t drain can be a major inconvenience. Dirty water filling up the tub and leaking out onto the floor is something no one wants to deal with. But before calling a repair person, there are several troubleshooting steps you can try yourself to get your dishwasher draining properly again.

Inspect the Drain Hose

The most common reason a dishwasher won’t drain is because there is a clog or kink in the drain hose. Start by pulling the dishwasher out from under the counter so you can access the drain hose.

Check the following:

  • Kinks – Run your hands along the hose to feel for any sharp bends or kinks that may be blocking water flow. Straighten the hose.
  • Clogs – Detach the drain hose from the sink drain or garbage disposal if possible. Hold it over a bucket and pour water through to flush out any debris. Reattach.
  • Leaks – Examine along the length of the hose for cracks or holes where water could be leaking out. If found, the drain hose will need replacing.
  • Connection – Make sure the drain hose is securely connected to the sink drain or garbage disposal outlet. Tighten if loose.
  • High Loop – Verify the drain hose is looped up high under the counter before going down to prevent backflow of dirty water.

Clean the Drain Pump Filter

Your dishwasher has a drain pump with a filter to catch food particles. If this gets clogged, it can stop proper drainage. To clean:

  1. Locate the drain pump filter. It is usually at the bottom front of the dishwasher.
  2. Twist counter-clockwise to unlock and remove the filter. You may need pliers if it’s stuck on tightly.
  3. Rinse filter under hot water to wash away debris. Use a toothbrush to dislodge stuck-on gunk.
  4. Replace the filter and twist clockwise to lock back in place.

This should allow normal water drainage again.

Check the Garbage Disposal

If your drain hose connects to the garbage disposal, a clog here can prevent proper dishwasher drainage.

To check:

  • Run the disposal to see if it sounds normal versus stalled.
  • Insert a screwdriver in the bottom of the disposal and turn the motor back and forth.
  • Disconnect the dishwasher hose and inspect inside the disposal outlet for obstructions.
  • Manually rotate the disposal blades using an Allen wrench in the bottom center.

If you find a clog, try to break it up with a disposal cleaning tool or drain snake. You may need to disconnect and thoroughly clean out the disposal if buildup is extensive.

Ensure Proper Air Gap

If your drain setup goes through an air gap device, check that it’s working right. This should be located on your sink or countertop.


  • Air gap is correctly installed above the water line of the sink.
  • Internal parts move freely and are not clogged.
  • Rubber cap sits properly over the main opening.
  • Connection tubes from dishwasher and garbage disposal are securely attached and free of kinks.

The air gap allows proper water flow without back pressure. Clean or replace if not functioning optimally.

Test Motor and Pump

The dishwasher motor and drain pump operate together to push out used water. Weakness in either can prevent good drainage.

To test:

  • Turn off power to the dishwasher at the breaker.
  • Remove outer panel to access motor and pumps.
  • Check if impellers turn freely.
  • Ensure wiring is intact with no burns or breaks.
  • Test for continuity with a multi-meter.

You may be able to clear out stuck impellers. But motors or pumps with electrical issues will need replacing.

Replace Defective Drain Valve

At the bottom of the dishwasher tub is a drain valve that opens to allow water to empty. If this fails, drainage problems occur.

Warning signs:

  • Water not emptying or emptying very slowly
  • Hearing buzzing or humming sound from valve area
  • Seeing leaking from valve during cycle

Replace the drain valve if diagnostic tests point to it as the cause. Make sure to shut off electrical power before accessing internal components.

Unclog a Clogged Sink Drain Line

If the dishwasher drain hose connects to the sink drain line, a clog here can back up the system.

To clear sink drain obstructions:

  • Use a plunger over the sink drain to pressurize the line.
  • Try snaking a drain auger down the drain line to hook and pull up debris.
  • Remove the p-trap under the sink to check for clogs.
  • Use a chemical drain cleaner or boiling water to dissolve obstructions.
  • For tough clogs, the drain pipe may need disassembly or replacement.

Once the sink drains freely again, the dishwasher should be able to drain out properly.

Adjust Cycle Settings

Some drainage problems are not mechanical issues, but rather improper cycle settings.

Try these adjustments:

  • Select heavier cycles like Pots & Pans to provide maximum water flow.
  • Disable HE (high-efficiency) options if available. These use less water.
  • Add Hi-Temp or Sani-Rinse options to utilize higher water temperatures.
  • Verify you are using rinse aid which helps optimize drainage.
  • Remove unneeded dishwasher safe rinse stop additive products.

Programming the optimal cycle should help with complete water drainage.

Inspect and Replace Door Gasket

A leaking door gasket can allow water to escape instead of properly draining out the bottom.

Inspect the rubber gasket around the door. If it’s damaged or deteriorating, replacement is required.

With a good seal, all water should stay contained until drained. Make sure to clean out any debris stuck in the gasket as well.

Adjust Dishwasher Legs

If the back or front of the dishwasher is not level, it can interfere with proper drainage.

To adjust:

  • Locate the leveling legs in the front corners.
  • If the back is too low, turn legs clockwise to raise it up.
  • If the front is too low, turn legs counter-clockwise to lower it.
  • Use a spirit level on top to verify dishwasher is level.

Proper leveling ensures water can drain completely out the pump. Check owner’s manual for further adjustment tips.

Increase Water Supply Pressure

Low water pressure going into the dishwasher can impede drainage. It may be too weak to push water out via the drain pump.

Try these tips:

  • Partially close sink faucets or other supply lines to increase dishwasher pressure.
  • Remove any supply line kinks reducing flow.
  • Examine supply filters on the dishwasher for debris and clean as needed.
  • Consider adding a booster pump if household water pressure reads low.

Proper water supply pressure is key for complete dishwasher drainage.

Summary of Dishwasher Drainage Fixes

While various issues can cause a dishwasher not to drain, there are several DIY troubleshooting steps you can take:

  • Inspect and clean drain hoses, pumps, valves and supply lines
  • Check for clogs in garbage disposal, sink drain, or air gap
  • Test and replace defective motor, pump or valve parts
  • Adjust cycle settings and dishwasher installation
  • Ensure door gasket is sealing tightly
  • Increase water supply pressure if too low

Following a systematic diagnosis approach can help isolate the cause of the drainage problem. Fixing these common issues often does not require a technician. But if you’ve tried all the troubleshooting tips without success, professional dishwasher repair may be the best solution.

Frequently Asked Questions About Dishwasher Drainage

Here are answers to some common questions about troubleshooting a dishwasher that won’t drain:

Why does my dishwasher have standing water in the bottom?

The most likely reasons are a clogged or kinked drain hose, clogged drain pump filter, blocked garbage disposal, defective drain valve, or improper sink drain hookup. Going through the troubleshooting steps will help identify the specific cause.

Why is dirty water backing up into my dishwasher?

Backflow of dirty water is usually due to an improper high drain loop, clogged garbage disposal, or faulty air gap device. Checking these areas will reveal the obstruction that needs clearing.

Why is water leaking onto the floor from my dishwasher?

If not coming from the door, leaks likely point to a hole in the drain hose, cracked pump housing, or deteriorated drain valve. Inspect these components closely to find and seal the leak.

My dishwasher hums but won’t drain – what’s wrong?

A humming noise means the pump is getting power but the impeller is jammed or broken. Try turning the impeller manually or replace the entire pump assemble if damaged.

How do I unclog my dishwasher drain?

Use a zip-it style cleaning tool to clear debris from the drain hose. Remove and clean the drain pump filter. And inspect the garbage disposal and sink drain lines for jams. This should get it draining freely again.

Why is dirty water pooling in the bottom of my dishwasher after a cycle?

For water left after a wash, the most common defect is a faulty drain valve that is not opening fully to allow complete drainage. Replace the valve if this is the diagnosed issue.


Dishwashers not draining properly can certainly be annoying. But as you’ve learned, there are a range of possible causes – from clogged hoses and filters to component malfunctions. Following DIY troubleshooting tips starting with the easiest solutions can help isolate the exact problem. Fixing basic clogs yourself saves repair costs. But for internal part replacements, professional dishwasher repair may be required. With the right diagnosis and service, you can get the appliance draining correctly again.