Dishwasher Not Draining? 9 Common Causes and Easy Fixes

You open the dishwasher expecting clean dishes… and instead you see a pool of dirty water at the bottom of the tub.

Annoying? 100%.
But in most cases, a dishwasher that isn’t draining is something you can fix yourself without calling a repair tech.

This guide walks you through:

The most common reasons your dishwasher won’t drain
Step-by-step fixes starting from easiest to more involved
When it’s time to call in a pro instead of guessing

By the end, you’ll know exactly where to start, what to check, and how to get your dishwasher draining normally again.

First: Is a Little Water Normal?

Before you panic, understand this:

Most dishwashers are designed to keep a small amount of water in the sump area at the bottom.
This helps protect the pump seals and keeps them from drying out.

Normal:

A shallow puddle in the very bottom recess (under the filter area)

Not normal:

Water covering the entire bottom of the tub
Water reaching the door when you open it
Food floating around and a strong smell

If you’ve got obvious standing water, let’s get into the causes and fixes.

Safety First: What to Do Before You Start

Before you touch anything:

Turn off the power to the dishwasher
- Either unplug it under the sink
- Or switch off the breaker that feeds the dishwasher
Scoop out excess water
- Use a cup or small container
- Mop up the rest with towels or a sponge

You don’t need the bottom bone-dry, but getting rid of most of the water makes it easier to see what’s going on.

Cause #1: Clogged Filter (Most Common and Easiest Fix)

Modern dishwashers have a removable filter at the bottom that catches food particles.

If it’s clogged, water can’t flow down into the drain pump properly.

How To Fix It

Open the dishwasher and remove the bottom rack.
Look for a circular or rectangular filter assembly on the floor of the tub.
Twist or lift it out according to the arrows/labels.
Rinse it under warm water and scrub off gunk with a soft brush.
Check the area below the filter for:
- Food chunks
- Glass shards
- Pasta, seeds, labels, etc.
Reinstall the filter securely.

Run a short cycle and see if your drainage has improved.

✅ This alone fixes a ton of “dishwasher not draining” issues.

Cause #2: Blocked Drain Basket or Sump Area

Even if the filter looks okay, food debris can get into the sump (the small reservoir under the filter) and block water flow.

What To Do

With the filter removed, shine a flashlight down into the opening.
Look for:
- Seeds (sunflower, popcorn, etc.)
- Small bones
- Glass pieces
- Paper or labels
Use a spoon, small brush, or gloved hand to carefully remove anything you see.
Rotate any small plastic covers that lift off to access deeper areas (depends on the model).

If the sump is packed with debris, clearing it can instantly restore proper draining.

Cause #3: Kinked or Clogged Drain Hose

Your dishwasher drain hose typically runs:

From the dishwasher
Up to an air gap or high loop
Then down to either the garbage disposal or sink drain

If this hose is kinked, blocked with gunk, or pinched, water can’t leave the machine.

How To Check It

Look under your sink and find the dishwasher drain hose (small rubber or plastic hose).
Make sure:
- It’s not sharply bent or crushed
- It rises in a loop (to prevent backflow)
If you suspect a clog:
- Detach the hose from the garbage disposal or sink drain (put a towel/bucket under it).
- Try gently blowing through it or flushing it with warm water.
- If it’s hard to clear, a small flexible brush or cable can help dislodge buildup.

Reattach it securely before testing again.

Cause #4: Garbage Disposal Knockout Plug Still In (New Install Issue)

If your dishwasher was recently installed or replaced, this one is big.

When a dishwasher drains into a garbage disposal, the disposal has a knockout plug inside the dishwasher connection port.

If the installer forgets to remove it, the dishwasher literally cannot drain through that connection.

How To Check

Look under the sink at the side of the garbage disposal.
Find where the dishwasher drain hose connects.
If this was newly installed and you suspect an issue:
- Turn off power to the disposal.
- Disconnect the hose.
- Use a screwdriver and light to look inside the port.

If the plug is still in place, it needs to be knocked out per the disposal’s instructions, and the small plastic disk must be removed from inside the disposal.

If you’re not comfortable doing this, a handyman or plumber can knock it out in minutes.

Cause #5: Air Gap or High Loop Problems

Some dishwashers drain through a sink-mounted air gap (a little metal cap near the faucet).
Others use a high loop in the hose secured under the counter.

If the air gap is clogged, your dishwasher can’t drain correctly.

How To Clear an Air Gap

Unscrew or pull off the air gap cover.
Check for food debris, gunk, or buildup inside.
Clean it out with a small brush and warm water.
Reassemble and test.

If you don’t have an air gap, make sure your drain hose loops up high under the counter before dropping down to the drain — if not, dirty sink water can wash back into the dishwasher and cause drainage issues.

Cause #6: Faulty Drain Pump or Pump Impeller Obstruction

The drain pump is the part that actually pushes water out of the dishwasher and into the drain line.

Two issues can happen:

The impeller (small fan/blade) is jammed by a piece of glass, bone, or debris.
The pump motor itself has failed.

How To Inspect for a Jam (Basic Check)

If you’re comfortable with light disassembly:

Disconnect power to the dishwasher.
Remove the bottom front kick plate (usually held by a couple of screws).
Locate the drain pump (small motor connected to the drain hose).
Depending on your model, you may be able to:
- Remove the pump cover
- Inspect the impeller
- Check for obstructions

If you find something stuck, carefully remove it and reassemble.

If the pump hums but doesn’t spin, or never activates, the motor may be failing and need replacement.

Cause #7: Clogged Sink Drain Where Dishwasher Connects

Sometimes the dishwasher is fine, but the sink’s drain line where the hose connects is clogged.

This is especially likely if:

Your sink is also draining slowly
Using the sink causes water to back into the dishwasher

How To Address It

Detach the dishwasher drain hose from the sink drain or disposal.
Check the port for sludge or hardened gunk.
Clean it thoroughly with a brush or small tool.
Consider cleaning the sink’s P-trap or using safe clog-removing methods on the sink drain itself.

If the sink drain is blocked, the dishwasher has nowhere to send water.

Cause #8: Using the Wrong Detergent (Excess Suds)

Using regular dish soap instead of dishwasher detergent can create a ton of suds that interfere with normal draining and leave a foamy mess at the bottom.

Even some cheap detergents can foam excessively in certain machines.

If you’ve recently changed what you’re using and suddenly see drainage issues along with lots of bubbles, this could be part of the problem.

Solution:

Run a rinse cycle with no detergent
Add a small amount of white vinegar to help cut suds
Use only proper dishwasher detergent going forward

Cause #9: Control Board or Cycle Issues

Less common, but possible: the dishwasher’s control board or timer isn’t properly triggering the drain cycle.

Signs this might be the case:

Dishwasher runs, stops, and never even attempts to drain
You don’t hear the usual draining noise at the end of the cycle
Other functions (like heating or washing) are also acting weird

At this point, if:

Filters are clean
Hoses are clear
Sink/disposal connection is open
You’ve ruled out clogs and mechanical issues

…then it may be time for a professional diagnosis or, in older units, considering a replacement.

When You Should Call a Professional

DIY is great — up to a point. You should call a pro if:

There are electrical burning smells or signs of melted components
You see leaks underneath the dishwasher or around the door
The unit is 10+ years old and needs frequent repairs
You’ve cleaned the filter, sump, hose, and connections, and it still won’t drain

Sometimes paying for one solid repair or replacing an ancient unit is cheaper in the long run than constantly fighting breakdowns.

How to Prevent Future Drainage Problems

Once you get your dishwasher draining again, keep it that way with a few simple habits:

Scrape, don’t rinse: Scrape off big food chunks, but you don’t need to fully wash dishes first.
Clean the filter monthly: It takes 2 minutes and prevents 80% of clogs.
Run hot water before starting: Let your sink’s hot water run for a few seconds so the dishwasher fills with hot water from the start.
Use the right detergent: Stick to quality dishwasher detergents and avoid regular dish soap.
Do a cleaning cycle regularly: Run an empty cycle with a dishwasher cleaner or a cup of white vinegar on the top rack.

FAQ: Dishwasher Not Draining

Why is there always a little water in the bottom of my dishwasher?
That’s normal. Most dishwashers keep a small amount of water in the sump to protect seals and the pump. Only large puddles covering the floor of the tub are a problem.

My dishwasher won’t drain and smells bad — what does that mean?
Usually, it means food debris is trapped in the filter, sump, or drain line. Cleaning the filter and sump area is the first step.

Can I run my dishwasher if it’s not draining properly?
You shouldn’t. Running it with a drainage issue can cause overflow, leaks, or damage to the pump.

Do I need a new dishwasher if it won’t drain?
Not usually. Most drainage problems are caused by clogs or minor issues you can fix yourself. Replacement is usually considered only when the machine is old or has multiple failing parts.