Standing water in the bottom of the tub after a cycle usually traces back to one of a few spots along the drain path. Here's how to check them safely, step by step.
Quick Diagnosis
Water is left standing in the bottom of the tub after the cycle finishes, sometimes an inch or more, often with a musty or sour smell.
Pull the lower rack and look at the bottom of the tub. Is the water cloudy, and can you see food debris or glass fragments floating in it?
A small puddle right around the filter recess is different from the tub being half full of water — the amount tells you how completely the drain path is blocked.
A little residual moisture directly around the filter is often normal; a full tub of standing water points to a real blockage somewhere between the filter and the drain pump.
Check the filter, look at the drain hose for kinks, and confirm the garbage disposal knockout plug was removed if this is a new install — all safe checks covered below.
If the water has been sitting for more than a day and smells strongly, or you notice heat or a burning smell near the pump area, stop and call for service.
What Can Cause This Problem?
Clogged lower filter assembly
Food debris, produce stickers, and small glass fragments collect in the fine mesh filter at the bottom of the tub over time. Once it's clogged enough, water can't pass through fast enough to clear the tub between cycles — this is the single most common cause of standing water.
Kinked or clogged drain hose
The corrugated hose that runs from the dishwasher to the disposal or air gap can get kinked when the unit is pushed back into place, or slowly build up grease and food residue inside. Either way, it restricts water flow even though the pump itself is working fine.
Garbage disposal knockout plug never removed
New garbage disposals ship with a factory plastic plug inside the dishwasher inlet port. If it isn't knocked out before the dishwasher hose is connected, it blocks the drain path completely — this is an extremely common cause after a kitchen remodel or disposal replacement.
Clogged air gap or high loop
The air gap fitting on the counter, or the high loop secured under the sink on installs without one, can collect grease and debris over months of use and slowly choke drain flow even when the hose and filter are clear.
Drain pump jammed by debris
A stray piece of glass, a bottle cap, or a chunk of food that made it past the filter can lodge in the pump's impeller housing. The pump may hum without moving water, or not run at all, depending on where exactly it's stuck.
Failed check valve letting water siphon back
Some dishwashers use a check valve to stop drained water from flowing back into the tub. If it sticks open, water drains normally and then re-enters the tub minutes later, which looks identical to a drain that never worked at all.
Drain pump motor failure or a control board that isn't commanding the drain
If the filter, hose, disposal connection, and air gap are all confirmed clear and water still won't move, the pump motor itself or the signal telling it to run becomes the more likely cause — confirming this needs direct testing, not guesswork.
What to Check First
Filter condition
SAFE FOR MOST HOMEOWNERS- How to check it
- Twist and lift the lower filter assembly out of the tub bottom.
- What the result may mean
- A clogged filter is the single most common blockage point in a dishwasher that won't drain.
- Normal
- Mesh screen and coarse trap are mostly clear.
- Abnormal
- Filter is clogged with food film, grease, or visible debris.
Standing water level and appearance
SAFE FOR MOST HOMEOWNERS- How to check it
- Look at the tub bottom after a full cycle and note the depth, color, and smell.
- What the result may mean
- Distinguishes a normal amount of residual moisture from an actual blockage worth tracing further.
- Normal
- Dry, or only a thin film of residual moisture.
- Abnormal
- Standing water more than a light film, cloudy or with a sour smell.
Drain hose path
SAFE FOR MOST HOMEOWNERS- How to check it
- With power and water supply off, gently pull the unit out and follow the hose from the dishwasher to the disposal or air gap connection.
- What the result may mean
- A kink or low sag restricts flow and can also trap debris at that point.
- Normal
- Hose runs in a smooth arc with no sharp bends.
- Abnormal
- Hose kinked, crushed under the cabinet, or sagging into a low loop.
Garbage disposal knockout plug (new installs)
SAFE FOR MOST HOMEOWNERS- How to check it
- If the disposal is new or recently replaced, shine a flashlight into the dishwasher inlet nipple on the side of the disposal.
- What the result may mean
- An unremoved plug blocks the drain path completely and is a very common oversight after a disposal swap.
- Normal
- Plug has been removed.
- Abnormal
- Plastic knockout plug is still in place.
Garbage disposal operation
SAFE FOR MOST HOMEOWNERS- How to check it
- Run the disposal for a few seconds to clear anything lodged in its chamber.
- What the result may mean
- If the dishwasher drains through the disposal, a clog there backs pressure up the shared line.
- Normal
- Runs freely with no resistance or clog.
- Abnormal
- Disposal itself is clogged or won't run.
Air gap or high loop condition
SAFE FOR MOST HOMEOWNERS- How to check it
- Locate the air gap cap on the countertop (if present) or the high loop secured under the sink, and check for buildup.
- What the result may mean
- A clogged air gap or loop restricts flow even with everything else clear.
- Normal
- Clear of debris.
- Abnormal
- Visible gunk or grease buildup inside.
Drain pump sound during the cycle
SAFE FOR MOST HOMEOWNERS- How to check it
- Start a cycle and listen closely during the drain portion, usually near the end.
- What the result may mean
- Humming without water movement suggests a jammed impeller; total silence suggests the pump isn't getting power or a signal to run.
- Normal
- A brief whirring or humming sound as water is pumped out.
- Abnormal
- A hum with no water movement, or complete silence.
Step-by-Step Checks
1. Remove and inspect the lower filter assembly
Twist the cylindrical filter housing counterclockwise, typically a quarter turn, and lift the whole assembly straight up out of the tub floor. Rinse both the fine mesh screen and the coarse outer trap under running water, checking for glass shards, produce stickers, or food fragments wedged in the mesh. Reseat it fully afterward — a filter that isn't locked back in correctly can itself restrict drainage.
2. Bail out standing water before continuing
Use a cup or a wet/dry shop vacuum to remove standing water from the tub bottom so you can see what you're working with. Never start a new cycle on top of standing water — the added fill water raises the risk of it overflowing onto the kitchen floor.
3. Check the drain hose behind the unit
With the water supply and power shut off, gently pull the dishwasher out from under the counter (most slide out on leveling feet once mounting screws are removed). Follow the corrugated drain hose from the dishwasher to where it connects at the disposal or air gap, feeling for a hard kink or a spot where it's pinched flat under the cabinet.
4. Confirm the disposal connection is actually open
If your dishwasher drains through a garbage disposal that was installed or replaced recently, use a flashlight to look into the dishwasher inlet nipple on the side of the disposal. Manufacturers ship disposals with a knockout plug in this port that has to be punched out with a screwdriver and hammer before the dishwasher hose is connected — leaving it in place is a very common cause of a drain that never works after a disposal swap.
5. Run the disposal and clear the air gap
Run the garbage disposal for several seconds to clear any food clog inside its chamber, since a clogged disposal backs pressure into the shared dishwasher drain line. If your sink has an air gap, a small chrome cylinder near the faucet, lift the cap and clear any visible debris from inside it.
6. Run a short cycle and observe the drain portion
Once the filter is clean and the hose is confirmed clear, run a short cycle and watch or listen specifically during the drain portion near the end. Note whether the pump makes sound without moving water, or makes no sound at all — either detail is useful information for a technician if the problem continues.
Look, Listen, Observe
look
- Cloudy, standing water covering the bottom of the tub after a full cycle — Confirms an actual blockage rather than normal light residual moisture.
- Glass fragments, produce stickers, or food debris caught in the filter mesh — Identifies the filter as the immediate blockage point.
- A sagging low point in the drain hose under the sink — Creates a trap where water and debris collect and restrict flow over time.
listen
- A humming sound during the drain cycle with no corresponding water movement — Suggests the pump impeller is jammed rather than the motor being dead.
- No sound at all when the drain portion of the cycle should be running — Points toward a pump not receiving power or a signal, or a failed motor.
observe
- Water drains, then reappears in the tub minutes later — Suggests a stuck check valve letting drained water siphon back in, rather than a blockage.
- A sour or musty smell from the tub — Standing water has been sitting long enough to go stagnant, common with a slow partial clog.
- Water backs up into the dishwasher when the garbage disposal runs — Points toward a disposal-side clog or an unremoved knockout plug on newer installs.
Easy Things You Can Try
- Clean the lower filter — Remove the twist-lock filter, rinse the mesh screen and coarse trap thoroughly under hot water, and scrub off any greasy film before reseating.
- Run the garbage disposal — Run it for 10-15 seconds before starting the next dishwasher cycle to clear any food clog that could be backing up into the shared drain line.
- Straighten a kinked drain hose — If you find a hose pinched under the cabinet or crushed against the wall, gently reposition it into a smooth arc and secure it so it can't kink again.
- Remove the disposal knockout plug — On a newly installed garbage disposal, use a screwdriver and hammer to knock out the plastic plug inside the dishwasher inlet nipple, then retrieve the plug so it doesn't fall into the disposal chamber.
Technician Tips
The filter is worth checking even if a homeowner says they already cleaned it — a filter that isn't fully reseated can look clean but still be sitting crooked enough to block flow, which is easy to miss without knowing exactly how it locks in.
When a customer says the dishwasher used to drain fine and now doesn't, I ask what changed in the kitchen recently — a new garbage disposal, a disposal that was recently cleared of its own clog, or new countertops raising the air gap height can all quietly cause this without the dishwasher itself failing.
A pump that hums without moving water almost always means something mechanical is jammed in the impeller housing, not that the motor itself is bad — that distinction matters because one is a quick fix and the other is a part replacement.
Diagnostic Tricks
- SAFE FOR MOST HOMEOWNERS
Pour a cup of water into the tub bottom after the filter is clean and reseated, then run just the drain portion of a cycle if your model allows selecting 'drain' or 'cancel/drain' directly — this isolates the pump and hose from the wash and rinse steps entirely.
- ADVANCED — BETTER FOR A TECHNICIAN
Disconnect the drain hose at the disposal end, with the disposal off and unplugged, and check whether water flows freely out of the hose when the drain cycle runs — if it does, the blockage is downstream at the disposal or air gap, not inside the dishwasher.
- ADVANCED — BETTER FOR A TECHNICIAN
Testing the pump motor's winding resistance with a multimeter can confirm a failed motor versus a jam, but it involves accessing the pump under the tub and should be left to a technician.
Error Codes
Many dishwashers show a code for this on the display. Codes vary significantly by brand and model, so check yours against the manufacturer's manual, or see our [Appliance error code guide](/blog/appliance-error-codes) for commonly documented codes. Appliance error code guide.
Can I Fix This Myself?
Cleaning the filter, running the disposal, checking for a kinked hose, and confirming a knockout plug was removed are all safe, tool-light checks that resolve a large share of drainage complaints.
Pulling the dishwasher out to inspect the full hose run, or disconnecting the hose at the disposal to isolate where a clog sits, takes some comfort with basic plumbing and reassembly.
Accessing the drain pump itself to clear a jammed impeller or test the motor requires removing the lower access panel and working around electrical connections — this is a technician-level repair.
What Not to Do
- Don't run another wash cycle on top of standing water — it raises the water level further and can overflow onto the kitchen floor once the fill valve adds more.
- Don't use chemical drain cleaners made for sink or toilet clogs in the dishwasher tub — they aren't designed for the pump and hose materials and can damage seals.
- Don't force the filter assembly if it doesn't twist free easily — forcing it can crack the locking tabs, and a cracked housing won't seat correctly even after the clog is cleared.
When to Stop Troubleshooting
- The pump area produces a burning or electrical smell during the drain cycle.
- You see water pooling near any exposed wiring or the base electrical connections under the unit.
- Standing water has been sitting for more than a day and you're not comfortable pulling the unit out yourself to check the hose.
- You've cleaned the filter, run the disposal, and confirmed the hose isn't kinked, and water still doesn't drain.
Don't Replace Parts Yet
Standing water can come from a clogged filter, a kinked hose, a blocked disposal connection, a stuck check valve, or a genuinely failed drain pump — and several of these produce the exact same puddle in the tub. Replacing a drain pump before confirming the hose and filter are actually clear means paying for a part that may not have been the problem, while a simple filter cleaning would have solved it. Tracing the water path in order, starting with the filter, is what actually narrows down which part, if any, needs to be replaced.
Frequently Asked Questions
Some models leave a small amount of residual water directly around the filter recess by design, but a full puddle across the tub bottom points to a blockage somewhere between the filter and the drain, most often the filter itself or a kinked hose.
Still not sure what's causing the problem?
Professional diagnosis can help identify the actual cause before replacing parts unnecessarily.