Because something between the tub and the drain is blocked, and the filter is the first suspect. Working out why there is standing water in your dishwasher runs in a fixed order, from the cheapest thing to check to the thing that needs a technician.
A small amount of water in the sump is normal on some machines. A puddle covering the floor of the tub is not.
Quick Answer
Check the filter first, then the drain hose for kinks and the high loop, then the air gap on the sink if you have one, then the garbage disposal connection. A new installation with water that never drains often has the disposal’s knockout plug still in place. A failed drain pump is the last suspect.
Key Takeaways
- A film of water in the sump can be normal. A puddle is not.
- The filter is the most common cause and the cheapest fix.
- A kinked or dropped drain hose stops drainage cold.
- A clogged sink air gap backs water into the tub.
- New installs often have the disposal knockout plug left in.
- A blocked sink drain shares the line and backs up too.
- Turn the power off before reaching into the base.
| Check | What you find | Difficulty |
|---|---|---|
| Filter in the tub floor | Food packed around it | Two minutes |
| Sump under the filter | Debris in the well | Two minutes |
| Drain hose | Kinked, crushed or sagging | Look under the sink |
| High loop or air gap | Missing loop, or a clogged gap | Easy to see, easy to fix |
| Garbage disposal inlet | Clogged, or knockout plug in place | Easy on a new install |
| Sink drain itself | Slow or blocked | Run the tap and watch |
| Check valve | Stuck, letting water back in | Harder |
| Drain pump | Silent, or humming without draining | Service call |
Step by Step
- Turn the power off at the breaker. You are about to put your hands in the base of an appliance.
- Bail the water out. A cup and a towel. You need a dry tub to see anything.
- Remove and inspect the filter. Twist it out, rinse it, and look at how much food was packed around it.
- Clear the sump beneath it. Wipe out the recess and check the drain opening at the bottom is clear.
- Look under the sink at the hose. Follow it for kinks, crushing behind a cabinet, or a sag holding water.
- Check for a high loop. The hose should rise up near the underside of the counter before dropping to the drain.
- Check the air gap if there is one. That small chrome cylinder on the sink deck clogs and backs water up.
- Check the disposal inlet. Run the disposal, and on a new install confirm the knockout plug was removed.
- Run the sink tap. A slow sink drain means the shared line is the problem, not the dishwasher.
- Run a cycle and listen. No pump noise at the drain phase, or a hum with no flow, points at the pump.
Some Water Is Supposed to Be There
Many machines keep a small amount of water in the sump between cycles. It keeps the seals from drying out and cracking.
The distinction is depth and coverage. A film you can barely see in the recess is by design. Water above the filter, covering the floor, is a drainage failure.
Cloudy, food-filled water is a different signal from clear water, and it points at the filter or the sump rather than at the pump.
Knowing which you have saves a service call. Our guide to whether to rinse dishes before loading covers the habit that keeps the most food out of there.
The Filter Is Usually It
Why it blocks
The filter catches food so the pump does not have to grind it. Enough of it and water cannot pass through at the rate the pump expects.
What it looks like
Softened food packed into the mesh, often with a layer of grease binding it together. Sometimes a label, a seed or a bone chip sitting across the opening.
The fix
Rinse under the tap with a soft brush, clear the recess it sits in, and refit it so it locks.
Preventing the repeat
Scrape properly and rinse the heaviest items. Our roundup of wire cleaning brushes covers reaching into a filter recess.
The Drain Hose and the High Loop
The drain hose runs from the pump, under the sink, to either the garbage disposal or a dedicated drain fitting. Three things go wrong with it.
Kinks are the simplest. A hose crushed behind a cabinet or bent sharply where it exits stops flow completely.
A missing high loop is the subtler one. The hose is supposed to rise close to the underside of the counter before dropping to the drain, which stops sink water siphoning back into the tub.
Sagging is the third. A low dip in the hose holds a pocket of dirty water that never clears. Our guide to deep cleaning a kitchen covers the under-sink area most people never look at.
The Air Gap and the Disposal
An air gap is the small chrome cylinder sometimes fitted on the sink deck. It prevents backflow and it clogs with the same debris the filter catches.
A clogged air gap sends water back toward the dishwasher, and it often sprays or leaks onto the counter as a clue.
Where the hose connects to a garbage disposal, the disposal itself can be the blockage. Running it clears the inlet.
On a new installation there is one classic error: the disposal ships with a knockout plug in the dishwasher inlet, and it has to be removed before connection. Leave it in and the dishwasher never drains from day one. Our guide to why a deep fryer trips the breaker covers the same category of installation-day fault on a different appliance.
When the Sink Is the Real Problem
The dishwasher and the sink share a drain line, so a slow sink is a dishwasher problem waiting to happen.
Run the tap and watch. If the sink drains slowly or gurgles, clear that first and retest the dishwasher before touching anything else.
Grease is the usual cause on a kitchen line, and it narrows a pipe gradually rather than blocking it suddenly.
Chemical drain cleaners are worth avoiding with a dishwasher connected, since residue can reach the machine’s seals. Our guide to disposing of cooking oil covers keeping grease out of the line in the first place.
What Needs a Technician
A drain pump that makes no sound during the drain phase has likely failed electrically. One that hums without moving water is jammed or worn.
A stuck check valve lets drained water flow back into the tub, which presents as water reappearing after a cycle finished clean.
Control board faults can skip the drain phase entirely while the rest of the cycle runs normally.
None of those are worth opening the machine for yourself. Our guide to cleaning burnt pots and pans covers the sink-based fallback while you wait, and our roundup of dish drying racks covers where those dishes go.
Related Reading
Frequently Asked Questions
Why is there standing water in my dishwasher?
Something between the tub and the drain is blocked. Check the filter first, then the drain hose for kinks and a missing high loop, then the sink air gap, then the garbage disposal connection. A failed drain pump is the last suspect.
Is a little water in the bottom normal?
On many machines, yes. A small amount in the sump keeps the seals from drying out and cracking. The distinction is depth: a barely visible film in the recess is by design, while water above the filter covering the floor is a failure.
What is a high loop and why does it matter?
The drain hose should rise close to the underside of the counter before dropping to the drain. That loop stops sink water siphoning back into the dishwasher. A hose that runs straight across with no rise lets water flow the wrong way.
What is the air gap?
The small chrome cylinder sometimes fitted on the sink deck. It prevents backflow and clogs with the same debris the filter catches. A clogged one pushes water back toward the dishwasher and often leaks onto the counter as a clue.
Why would a brand new dishwasher never drain?
Most often the garbage disposal’s knockout plug. Disposals ship with a plug sealing the dishwasher inlet, and it has to be punched out before the hose is connected. Leave it in and the machine cannot drain at all.
Could the sink be causing it?
Yes, since they share a drain line. Run the tap and watch: a slow or gurgling sink means clear that line first and retest. Grease narrows a kitchen drain gradually rather than blocking it all at once.
Should you use drain cleaner?
Avoid it with a dishwasher connected, because residue can reach the machine’s seals and components. Mechanical clearing of the trap and line is the safer route, and keeping grease out of the drain prevents most of the problem.
When do you need a technician?
When a drain pump makes no sound during the drain phase, hums without moving water, or when water reappears in a tub that drained properly, which suggests a stuck check valve. Control board faults can also skip the drain phase entirely.
