Dishwasher Not Draining
Standing water usually means one of three mechanical choke points.
Compiled by DIY Repair Guide · reviewed 2026-09-23 ·how we research these
A dishwasher with standing water in the bottom is usually blocked by food debris in the sump filter, a kinked drain hose, or a solid knockout plug left inside a newly installed garbage disposal. At DIY Repair Guide, we compiled this diagnostic path to help homeowners isolate the exact failure point in fifteen minutes using basic household tools.
Working through the drain path in mechanical sequence solves the vast majority of drainage failures without replacing components. You only need an appliance technician when the electric drain pump fails mechanically or the internal motor windings burn out.
How Water Exits the Machine
Water leaves the wash tub through a sequential path of mechanical screens, an electric pump, and flexible drain lines. Understanding each connection point shows exactly where water can stall during the drain cycle.
The wash water gathers in the sump basin at the lowest point of the tub, passing through a removable mesh filter that traps coarse food scraps. Directly below that screen sits the electric drain pump, which drives an impeller to force dirty water into the ribbed drain hose under your kitchen counter.
The flexible hose routes either through an elevated high loop fastened to the underside of the countertop or through a dedicated deck-mounted air gap. From there, the discharge line ties directly into the side inlet nipple of your garbage disposal or connects straight to a sink branch tailpiece.
Inspect and Clean the Sump Filter
A clogged cylindrical mesh filter at the bottom of the tub is the single most common reason why a dishwasher is not draining water in the bottom. Modern dishwashers rely on manual-clean fine mesh screens rather than noisy internal macerators, meaning solid grease and food particles inevitably accumulate across the screen pores over several weeks.
Pull out the lower dishrack to expose the floor of the appliance. Turn the cylindrical plastic filter counterclockwise one quarter turn, lift it straight up, and pull out the flat metal coarse screen sitting beneath it.
Rinse both filter parts under hot running tap water with a soft nylon brush and mild dish soap to clear cloudy calcium deposits and trapped debris. Before snapping the filter back into place, reach into the open sump with a flashlight to verify that stray toothpicks, broken glass, or seeds are not wedged beneath the screen.
If you experience your dishwasher not draining after cleaning filter assemblies, check that the mesh cylinder clicked completely into its alignment notches. An improperly seated filter lets debris wash underneath, which jams the plastic impeller blades immediately below the sump.
Check the Garbage Disposal Knockout Plug
If your dishwasher is not draining after installing new garbage disposal units, the unremoved factory knockout plug is almost certainly the cause. Every new garbage disposal comes from the factory with a solid plastic barrier inside its dishwasher inlet nipple to prevent sink leaks in homes that lack a dishwasher.
When an installer mounts the disposal without knocking out this inner plastic disk, dirty dishwasher water hits a solid wall and backs up into the tub during the very first run. The dishwasher fills with water normally during the wash phase, but it cannot discharge a single drop through the inlet.
To clear the port, disconnect the dishwasher drain hose clamp from the disposal inlet tube. Place a flathead screwdriver against the plastic plug visible inside the small metal nipple, strike the screwdriver handle firmly with a hammer until the plug snaps loose, and fish the loose plastic plug out through the top sink opening of the disposal before reconnecting the hose.
Always retrieve the knocked-out plastic disc from the disposal grind chamber before restoring power. Leaving the loose plug inside the chamber will jam the rotating shredder ring when you next flip the disposal wall switch. If your disposal hums after installation, see our guide on fixing a humming garbage disposal.
Clear the Drain Hose and Verify the High Loop
A kinked, pinched, or drooping drain hose prevents the small electric pump from pushing water up and out of the machine. The discharge hose must rise above the sink basin flood level before descending to the disposal inlet to prevent dirty sink rinse water from back-siphoning into the tub.
Inspect the flexible hose where it routes through the cabinet wall partition under the sink. Pull out stored cleaning supplies, trash bins, or heavy cookware that may have crushed the ribbed plastic tubing flat against the cabinet base.
Make sure the flexible line arches all the way to the underside of the countertop in a secure high loop held in place by a bracket or metal strap. If the hose droops flat along the cabinet floor, gravity pulls dirty sink runoff backwards through the line, causing your dishwasher filling up with water and not draining clean.
Rule Out Downstream Kitchen Plumbing Blocks
A kitchen drain clog downstream of the sink trap will push dirty sink water straight back into the dishwasher wash tub. Because the dishwasher discharge hose connects above the primary sink P-trap, any partial obstruction in the wall drain forces grease and gray water up into the appliance through the line of least resistance.
Run your kitchen sink faucet on full hot water for sixty seconds while watching the basin. If water rises up the sink bowl or drains out with a sluggish gurgling noise, your drainage problem sits in the building plumbing pipes rather than the dishwasher itself.
Clear the kitchen drain line or disposal before attempting further appliance diagnostics. Homeowners can resolve typical kitchen line grease blocks using the steps outlined in our tutorial on how to unclog a drain line.
Diagnose the Drain Pump and Impeller
When the sump filter is spotless, the drain hose is open, and the sink pipes flow freely, an electric drain pump malfunction is the remaining physical cause. The drain pump uses an electric motor to rotate a small set of plastic blades that move wastewater through the check valve.
Listen closely to the base of the machine during the final two minutes of a test cycle. A healthy pump produces a steady low motor whir followed by the sound of gushing water under the sink basin. A loud humming buzz with zero water flow indicates that a foreign object has jammed the impeller or the motor bearings have locked up.
Accessing the pump housing requires removing the lower toe-kick panel or sliding the appliance out from under the counter to reach the under-tub bracket. Because this step involves live 120-volt wiring leads and water seals that cause under-cabinet leaks when misaligned, replacing an internal pump motor is work best left to a professional appliance repair technician.
Symptom to Cause Diagnostic Table
Compare the specific pattern of water left in your machine against this compiled diagnostic table to find the quickest fix for your dishwasher not draining completely.
| Symptom | Primary Cause | Corrective Action |
|---|---|---|
| Deep standing water, fresh install | Disposal knockout plug left in place | Disconnect hose, punch out plug, retrieve plastic disc |
| Shallow standing water over filter | Clogged mesh screen or sump basin | Remove cylindrical filter, scrub mesh with soft brush |
| Dishwasher not draining all the way | Kinked hose or missing high loop | Reroute ribbed hose, strap high loop to counter frame |
| Motor hums loudly, no water movement | Debris jammed in pump impeller | Cut power, clear pump chamber, or call a technician |
| Water rises in sink when draining | Downstream sink drain clog | Clear kitchen trap line, check plumber cost if persistent |
| Water returns hours after cycle | Dirty sink water back-siphoning | Install high drain loop or clean deck air-gap valve |
When to Repair Yourself and When to Hire Help
Most drainage faults cost nothing to fix because clearing a dirty filter, straightening a pinched drain hose, or punching out a disposal plug requires only ten minutes and a screwdriver. These three mechanical checks resolve most standing-water complaints before a technician visit is ever needed.
You should call a qualified appliance technician or a licensed plumber when the pump motor hums continuously without spinning, water leaks from beneath the tub frame, or downstream home plumbing lines stay blocked. If you need to bring in a professional for stubborn drain lines under the sink, consult our guide to average plumber costs to budget for the service visit.
Before calling for professional service, verify that the machine has completed its full cycle using whatever manual drain or cancel function your specific model provides, per its owner's manual, to trigger a fresh drain attempt.
Common questions
Why is my dishwasher not draining completely?
A dishwasher not draining completely is usually caused by a partially clogged mesh filter in the sump or a sagging drain hose that lacks a high loop. Scrub the bottom filter screen under warm water and make sure the ribbed discharge line loops higher than your sink connection before replacing any mechanical parts.
Why is my dishwasher not draining after installing a new garbage disposal?
New garbage disposals contain an internal plastic knockout plug inside the small dishwasher inlet nipple that blocks wastewater flow until removed. Remove the drain hose, knock the plastic plug out into the disposal chamber with a flathead screwdriver and hammer, and retrieve the plastic disk from inside the disposal before running the dishwasher again.
How do I clean my dishwasher filter?
Rotate the cylindrical filter in the center of the tub floor counterclockwise one quarter turn and pull it straight up, then lift out the flat metal coarse plate beneath it. Rinse both pieces under hot running tap water using a soft nylon brush and mild dish soap to remove grease and food film, then lock them firmly back into the sump basin.
Why does my dishwasher fill with water and not drain?
When a dishwasher fills with water and will not drain at the end of the cycle, the water supply valve works but the discharge path is completely obstructed or the drain pump has failed. Check first for a blocked disposal inlet nipple or a foreign object wedged in the pump impeller before scheduling a pump replacement.
What should I do if my dishwasher is not draining after cleaning the filter?
Verify that the plastic filter assembly was twisted back into its locked alignment position, as an unseated filter lets stray debris slip past and jam the pump impeller blades below. Next, inspect the flexible discharge hose under your sink for sudden kinks or crimps caused by moved cabinet items.
How much does it cost to fix a dishwasher that will not drain?
Clearing a clogged filter, unkinking a hose, or removing a disposal knockout plug costs nothing as a DIY fix. A failed drain pump is a parts-and-labor repair, and cost varies by dishwasher model and local labor rates, so get a quote from a licensed appliance repair technician rather than assuming a figure before they inspect the unit.