Dishwasher Not Draining — Step-by-Step Diagnostic Guide

The drain hose runs from the drain pump outlet to the air gap or directly into the sink drain pipe under the sink. Kinks, pinches, or accumulated debris in this hose will block drainage.

• Pull the dishwasher out from under the counter (disconnect power first).
• Trace the drain hose from the pump outlet to its termination point.
• Check for kinks where the hose bends around cabinet walls or sharp corners — a crushed hose is common when a dishwasher is pushed too far back.
• Disconnect the hose at both ends and blow through it or run water through it to check for blockage.
• If debris is visible, flush with hot water. For heavy grease buildup, use a small bottle brush to scrub the interior.
• Reconnect with hose clamps — ensure clamps are tight but don't crush the hose.

Not all dishwashers have an air gap — some use a high loop where the drain hose rises and then drops to the sink connection. Both serve the same purpose: prevent backflow.

• Look at the chrome cylinder next to your faucet. That's the air gap.
• Remove the top cap (twist or unscrew). Use a flashlight to see inside the cylinder.
• Clean out any debris with a small bottle brush and hot water.
• The air gap connects to the drain hose underneath the sink. Check that connection too — remove the clamp, disconnect, and inspect.
• Some homes have no air gap (just the high loop under the counter). In that case, skip this step and go to Step 4.

If the dishwasher drain hose connects to the inlet knockout on the garbage disposal, a backed-up disposal will send water back into the dishwasher. This is a common misdiagnosis when the filter and hose both appear clean.

• Run the garbage disposal — if it hasn't been used recently, debris may have accumulated.
• Check the knockout plug inside the disposal's dishwasher inlet. On new disposals, this plug must be removed with a punch or screwdriver. If it's still in place, water can't flow through.
• If the disposal is old and corroded, or has a jammed flywheel, it won't accept water — and neither will the dishwasher drain line. See our full garbage disposal troubleshooting guide for diagnosing a humming or jammed disposal.
• After clearing the disposal, run a full rinse cycle on the dishwasher with no dishes to test.

The drain pump is the last component before water leaves the machine. If the filter, hose, air gap, and disposal are all clear, the pump is the likely culprit.

• Locate the drain pump — usually accessed from the front (behind the kick panel) on front-control dishwashers, or from below on top-control models.
• Disconnect power. Place towels under the dishwasher.
• Remove the kick panel (2–4 screws at the bottom front). The pump assembly is attached to the sump assembly at the bottom of the tub.
• Inspect the pump housing — look for any debris (glass, string, bone fragments) wrapped around the impeller. The impeller is a small plastic fan behind the pump cover.
• Clear any debris. Reassemble and test.
• If the impeller is intact but the pump is silent when it should be running, the motor is failed — the pump needs replacement.

Some dishwashers use a drain solenoid (electric valve) instead of a motor-driven pump for the drain function. More commonly, a loose or corroded wire connection at the drain pump prevents it from receiving power.

• Set a multimeter to continuity (Ω). Disconnect the wire harness to the drain pump.
• Test the pump motor winding — expect 10–50 Ω across the motor terminals for a functioning pump. Open circuit (OL) = failed motor.
• Check all wire connectors at the pump for corrosion, burn marks, or looseness. Reconnect any loose connectors.
• If connectors are corroded, clean with electrical contact cleaner or replace the connector housing.
• Inspect the wiring harness running from the control board to the pump for any chafed or broken wires.

The main control board orchestrates every cycle — including signaling the drain pump to activate. A failed board may not send the drain command at all. Before replacing the board, confirm all drain-side components are verified in Steps 1–6.

• Signs of a bad control board: drain pump never activates, cycle ends with standing water, no error codes (some models show nothing on the display), and all other components test OK.
• Check for visible burn marks or swollen capacitors on the control board — a common failure pattern.
• If the board shows visible damage (dark scorching, melted components), replacement is warranted.
• Control boards are model-specific. Find the part number on the board itself or in the service manual. Replacement boards typically cost $150–$400 depending on the brand.
• On Bosch, Miele, and Samsung dishwashers, the control board is a frequent failure point — budget accordingly.