Quick diagnosis (60-second check)
- Is the sink/disposal draining normally? If the sink is backed up, clear that first.
- Just installed a new garbage disposal? The dishwasher inlet knockout plug may not have been removed.
- Open the door mid-cycle recently? Restart a full drain cycle—some models won’t drain until the cycle completes.
What you’ll need
- Screwdriver, pliers
- Towels + small container or wet-dry vac
- Soft brush + white vinegar
- Flashlight
Safety first
Unplug the dishwasher or switch off the breaker. Turn off the water supply if you’ll disconnect hoses.
1) Clogged Filter & Sump (Most Common)
The issue: Food sludge blocks the fine filter and the sump inlet, so the pump can’t move water out.
How to fix it: Pull the bottom rack. Twist out the filter(s). Rinse under warm water and scrub. Check the sump opening for glass, seeds, labels; remove debris. Reinstall firmly.
2) Air Gap Blocked (If You Have One)
The issue: The small cap by the faucet hides an insert that can clog and mimic a bad pump.
How to fix it: Pop the cap, pull the insert, rinse thoroughly, and clear the side ports. Re-seat the insert and cap.
3) Disposal Knockout Still In
The issue: New garbage disposals ship with a solid knockout in the dishwasher inlet; water can’t pass.
How to fix it: Loosen the dishwasher hose at the disposal. Insert a screwdriver into the inlet, knock out the plug, remove the loose disk, reattach the hose with a tight clamp.
4) Kinked or Grease-Clogged Drain Hose
The issue: A crushed bend or greasy buildup throttles flow and causes back-ups.
How to fix it: Inspect the entire hose run. Straighten kinks and move items under the sink. Detach the sink end into a bucket; flush warm water through. Replace if brittle.
5) No High Loop / Backflow
The issue: Without a high loop or air gap, sink water runs back into the tub, leaving standing water.
How to fix it: Route the drain hose in a high loop (top of the cabinet, secured with a clamp/zip tie) or install an air gap per local code.
6) Stuck Check Valve
The issue: The flapper at the pump outlet sticks closed or warps, blocking drainage.
How to fix it: Access the check valve (model-specific). Free or replace the flapper/insert. Ensure it swings freely and seals only against backflow.
7) Drain Pump Jammed or Failed
The issue: Impeller blocked (hums) or motor not running (silent).
How to fix it: With power off, remove the pump cover and clear debris (glass, pits). Restore power and run a drain cycle. If it’s powered but won’t spin, replace the pump.
8) Float Switch Stuck “Full”
The issue: The dishwasher thinks it’s overfilled and won’t advance to drain.
How to fix it: Locate the float (usually a dome on the floor). Lift and drop; it should move freely and click. Clean around it. Test/replace the microswitch if needed.
9) Oversuds / Wrong Detergent
The issue: Excess foam stalls drainage and confuses water level sensing.
How to fix it: Use dishwasher-only detergent. If oversudsed, add a cup of cold water and run a drain. Repeat until clear; then run a hot rinse.
10) Control Glitch or Wiring Fault
The issue: The board never energizes the drain pump, or a harness is loose.
How to fix it: Hard reset: kill power for 5 minutes, restore, and run a short cycle. If the pump never gets power (multimeter required) or errors persist, schedule service.
Need Help?
If you’ve cleaned the filter/air gap/hose and it still won’t drain, the pump or controls likely need replacement. For fast local service in Staten Island, book via dryer repair.