Dishwasher Not Draining? Common Causes & How to Fix It

There is a specific kind of panic that sets in when you open your dishwasher door. You expect to see clean, dry plates. Instead, you are greeted by a pool of grey, murky water at the bottom of the tub. It smells bad. It looks gross. And immediately, you start seeing dollar signs.

Here in Houston, Texas, where the humidity already makes everything feel damp, finding standing water in your appliance is the last thing you want.

We get calls about this every week at Homevisory. Homeowners think the machine is broken. They think the motor burned out. Usually, they are wrong.

If your dishwasher is not draining, it is rarely a catastrophic mechanical failure. It is usually a clog. A blockage. Something is stopping the water flow from leaving the machine and entering your house pipes.

Before you call a professional service and spend $200 just for them to show up, you can probably fix this yourself. It takes a little bit of work, and you might get your hands wet, but it is better than buying a new machine.

Here is the step-by-step process we use to diagnose and fix a dishwasher that won’t drain.

Safety First: Don’t Get Shocked

Before you stick your hands in that water, you need to be safe. Dishwashers mix electricity and water. That is a dangerous combination if you start taking things apart.

Find the breaker box in your garage or basement. Flip the switch for the dishwasher to “Off.” If you can’t find the breaker, unplug the unit. Usually, the plug is under the kitchen sink.

Don’t skip this. You don’t want the machine to start a cycle while your fingers are near the drain pump impeller.

Step 1: Bail Out the Standing Water

You can’t see the problem if it is covered in three inches of dirty water. You need to get that water out.

• Use a cup: Scoop the water out into a bucket or the sink.
• Towels: Soak up the last bit at the bottom.
• Wet vac if you have one: This is the fastest way.

Once the bottom of the tub is visible, you can start looking for the culprit.

Step 2: Check the Filter (The Usual Suspect)

We talked about this in our dishwasher cleaning guide, but it is worth repeating because it is the number one cause of drain blockage.

Modern dishwashers have a filter system at the bottom of the tub. It catches the food debris so it doesn’t clog the pump. But if you never clean it, the filter itself becomes the clog. It gets coated in grease, paper labels from jars, and pieces of bone. If water can’t get through the filter, it can’t get to the drain pump.

What to do:

1. Remove the bottom rack.
2. Twist and unlock the filter cylinder.
3. Lift it out.
4. Remove the mesh screen below it (if your model has one).
5. Look at the “sump” area (the hole where the filter sits). Is there chunks of food in there? A piece of broken glass? A popcorn kernel?
6. Clean the filter in the sink with hot water.
7. Reach into the sump with a paper towel and wipe it out. Be careful of glass.

If the filter was covered in slime, that was likely your problem. Put it back together and try to run a “Rinse” cycle. If it drains, you’re done.

Step 3: The Garbage Disposal Connection

This is the second most common issue we see, especially if you just installed a new garbage disposal.

Your dishwasher drain hose connects to the disposal under the sink. If the disposal is full of food, the dishwasher cannot force water into it. The water flow is blocked by the potato peels you shoved down the drain last night.

Run the disposal: Turn on the water in the sink and run the disposal for thirty seconds. Ensure it is clear.

The Knockout Plug: If you just bought a new disposal and now the dishwasher won’t drain, we know exactly what happened. New disposals come with a plastic “knockout plug” inside the inlet port. You have to break this plug out with a hammer and screwdriver before connecting the hose. If you forgot to remove it, the hose is connected to a solid wall of plastic. The water has nowhere to go.

Take the hose off, punch out the plug, and fish the plastic piece out of the disposal.

Step 4: The Drain Hose

The drain hose is the corrugated plastic tube that runs from the pump to the sink drain or disposal. It is usually ribbed. Because it is flexible, it can get kinked. Think of it like a garden hose. If you step on the hose, the water stops.

If you shoved a box of detergent or a trash can under your sink, you might have pinched the dishwasher hose against the wall.

Inspect the hose:

• Grab a flashlight.
• Look under the sink.
• Trace the hose from the disposal back through the cabinet wall.
• Check for any heavy items sitting on it.
• Straighten out any kinks.

Check for clogs inside the hose:

Sometimes the clog is inside the tube. Grease settles in the ridges of the hose and hardens.

To check this, put a bucket under the sink. Disconnect the drain hose from the disposal or air gap. Aim the end of the hose into the bucket. Close the dishwasher door and run a “Drain” or “Cancel/Reset” cycle.

• If water shoots out into the bucket with force, the blockage is in the disposal or the sink plumbing, not the dishwasher.
• If water just trickles out or nothing comes out, the blockage is in the hose or the pump.

Step 5: The Air Gap

Do you have a little silver cylinder sitting on the back corner of your sink? That is called an air gap. It prevents dirty sink water from backflowing into the dishwasher. It is code required in many states.

These things clog all the time. If the air gap is clogged, the water will pump out of the dishwasher but get stuck at the air gap. It might spill out onto the counter or back up into the machine.

How to clean it:

1. Pull the silver cover straight up. It comes right off.
2. Unscrew the plastic cap underneath.
3. Look inside. You will probably see a blockage of grease or food.
4. Use a small bottle brush or an air gap brush to push the gunk out.
5. Pour some hot water down it.

If you don’t have a brush, you can use a wire hanger, but be gentle. You don’t want to poke a hole in the tube.

Step 6: The Drain Valve and Bracket

If the filter is clean, the hose is clear, and the disposal is empty, but water still stands in the tub, we have to look deeper.

Some older models use a drain valve solenoid. This is a little mechanical gate that opens to let water out. If the solenoid burns out, the gate stays shut.

To check this, you usually have to remove the toe kick (the panel near the floor) beneath the door. You will see the motor and the pump. Look for a moving arm near the motor. When the drain cycle starts, that arm should move. If it doesn’t, the solenoid might be bad.

Honestly, if you are down here messing with solenoids and multimeters, you might want to call a pro. But there is one more thing you can check yourself.

Step 7: The Drain Pump Impeller

The drain pump has a little plastic propeller inside it called an impeller. It spins to push the water. Sometimes, a piece of broken glass or a hard pistachio shell gets past the filter and jams the impeller. If the impeller can’t spin, the water doesn’t move.

On many models, you can access this from inside the tub.

1. Remove the filter assembly again.
2. Look for a small cover held down by a screw (usually a Torx screw).
3. Remove the cover.
4. You will see the little white propeller.
5. Try to spin it with your finger. It should spin with a little bit of magnetic resistance, like a bouncy feel.
6. If it is stuck solid, something is jammed.
7. Take a pair of needle-nose pliers and look for the debris. Pull it out.

Once it spins free, put the cover back on.

Warning: Be very careful. If there is glass in there, it is sharp. Wear gloves or use the pliers.

Step 8: The High Loop Method

This isn’t a fix for a clog, but it is a fix for water flowing back in.

If you don’t have an air gap, your drain hose needs a “high loop.” This means the drain hose should go up to the top of the cabinet (underside of the counter) and then come back down to the disposal. Gravity stops the dirty sink water from running down the hose into your dishwasher.

If your hose lays flat on the bottom of the cabinet, you will constantly have standing water.

Get a zip tie or a bracket. Attach the hose to the top of the cabinet wall. This is a simple plumbing fix that saves a lot of headaches.

When to Call a Professional Service

We love DIY here at Homevisory, but sometimes you have to throw in the towel.

If you have checked the filter, the hose, the air gap, and the disposal, and the pump is making a loud buzzing noise but not moving water, the pump motor is likely dead. Replacing a pump is doable, but it involves pulling the whole machine out of the cabinet.

If the electronics board is frying or the control panel is flashing codes you can’t reset, call a tech.

Prevent the Clog

The best way to fix a drain issue is to not have one.

• Don’t treat it like a trash can. Scrape your plates.
• Run hot water. Run the sink until it’s hot before starting the load.
• Use the right soap.
• Clean the filter monthly.

It is easy to forget this stuff. We all have busy lives. The house needs so much maintenance that it feels like a second job.

That is why we created the Homevisory home task manager. It is a free tool for homeowners. You sign up, tell us what appliances you have, and we create a custom schedule for you. We remind you when to clean the filter. We remind you when to flush the drain line. We take the thinking out of it.

Sign up for the Homevisory home task manager today. It is free of charge. It helps you keep your home running smooth so you don’t end up bailing water out of a dishwasher at 9 PM on a Tuesday.

Final Thoughts

Standing water looks scary, but it is usually just a wad of wet food stuck in a hose. Don’t panic. Just start at the filter and work your way out to the sink.

I keep a screwdriver and a bottle brush under my sink just for this. I check my drain loop every month because I hate the smell of old water.

Follow these steps, and you will get that water flowing again. Good luck.