Dishwasher Not Draining but Filter Is Clean: A Practical Troubleshooting Guide
If your dishwasher finishes a cycle but water remains in the tub even though the filter is clean, don't panic. A blocked filter is only one of several possible causes. This guide walks you through safe diagnostics, likely causes, targeted repairs, and preventative maintenance so you can restore proper drainage without unnecessary expense.
Before you begin: safety and preparation
- Disconnect power: unplug the dishwasher or switch off the breaker to avoid electrical shock while working near the pump or wiring.
- Turn off the water supply if you'll be disconnecting hoses or working on the disposal connection.
- Have basic tools ready: bucket, towels, pliers, screwdriver set, adjustable wrench, flashlight, and a multimeter if you'll test electrical components.
- Wear gloves to protect hands from sharp objects inside the sump and to keep them clean.
Common causes when the filter is clean
- Drain hose: kinked, clogged, or improperly routed (too low or high) preventing gravity-assisted flow.
- Garbage disposal or knockout plug: the dishwasher drain may connect to a disposal that still has the inlet knockout plug in place, or the disposal is clogged.
- Air gap or vent blockage: an air gap (on the countertop or sink) or a vent integrated in the line can become blocked with debris.
- Check valve or drain flapper failure: these prevent backflow; if stuck closed or broken, the pump can't expel water.
- Drain pump or motor failure: the pump may hum but not turn, or the impeller may be broken or jammed by foreign objects.
- Float switch or water-level sensor: a stuck float or faulty sensor can tell the control board that the tub is empty, skipping the drain.
- Control board or drain solenoid malfunction: electronic issues that fail to signal the pump to run.
- Sump clog or foreign object: small shards, food debris, coffee grounds, or broken glass can jam the impeller or clog the sump even when the visible filter is clean.
Step-by-step diagnostic checklist
- Run a drain cycle and listen carefully. A working pump will make a distinct motor sound. Humming with no water movement often means a jammed impeller or stuck pump.
- Check the drain hose. Inspect for kinks or bends behind the dishwasher; remove and flush the hose into a bucket to confirm it's clear.
- Inspect the garbage disposal. If you recently installed a new disposal, ensure the knockout plug was removed. Run the disposal and check for blockages.
- Look at the air gap (if present). Remove the cap and clean away debris or sludge that can back up the line.
- Access the kickplate and remove any covers to reach the drain pump. Visually inspect the pump inlet and impeller area for obstructions.
- Test the drain pump electrically: with power off remove the pump wiring harness and use a multimeter to check for continuity. No continuity may indicate a burned motor.
- Test the float switch: physically move the float up and down; it should click and cause the control to register a change. Test continuity on the switch if available.
- If the pump runs but the dishwasher still won't drain, check the check valve on the pump outlet and the hose connection; replace any brittle or damaged one-way valves.
Quick checklist: inspect drain hose, check garbage disposal, clear air gap, test pump for hum and rotation, check float/sensor, inspect check valve.
How to clear specific problems
- Clearing a clogged drain hose: disconnect the free end at the sink or disposal, run water through it, and use a flexible brush or small snake if needed. Replace the hose if softened or collapsed.
- Removing the disposal knockout plug: with the disposal turned off and trapped water drained, remove the dishwasher inlet on the disposal and pull out the broken-out plug-many installers forget this step.
- Cleaning the air gap: remove the top cap and plunger, flush out trapped food, and reassemble. A blocked air gap causes slow or no draining and can lead to backflow.
- Clearing a jammed pump: after power is off, remove the bottom access and manually rotate the pump impeller with pliers if reachable. Remove any debris, hair, glass, or plastic fragments.
- Replacing the drain pump: if the pump motor shows no continuity, or it spins but the impeller is damaged, replacement is usually straightforward and inexpensive-consult your model's service manual for the correct part and steps.
- Addressing a faulty check valve: replace the valve if it's stuck or cracked. A failed check valve allows backflow or prevents forward drainage.
When to call a professional
- Electrical uncertainties: if you're not comfortable testing circuit continuity or tracing control board signals, call a technician.
- Complex pump access: some dishwashers require tilting or removing cabinetry to access the sump/pump-this can damage cabinets if done improperly.
- Persistent intermittent issues: if the problem recurs after replacing hoses or pumps, the control board or wiring may be at fault and needs a professional diagnosis.
- Warranty concerns: if the appliance is under warranty, consult the manufacturer or authorized service to avoid voiding coverage.
Preventive maintenance to avoid future drain issues
- Run a monthly maintenance cycle: use dishwasher cleaner or run a hot cycle with a cup of white vinegar (manufacturer recommendations first) to dissolve grease and mineral buildup.
- Scrape plates before loading: large food scraps and fibrous wastes (potato peelings, corn husks) cause clogs; dispose of large debris in the compost or trash.
- Keep the air gap and disposal inlet clean: periodic inspection prevents clogs that lead to standing water.
- Replace old hoses every 5–7 years: rubber hoses can collapse internally and prevent proper drainage.
- Inspect the dishwasher door seal and tub for broken glass or foreign objects after a broken dish to prevent pieces from blocking the impeller.
Kitchen maintenance connections
While troubleshooting drainage, it's a good time to assess other kitchen-workspace items. For example, if you're doing general maintenance you may also be thinking about sharpening tools-there's a big conversation around sharpening japanese vs german kitchen knives and the right technique will extend blade life and reduce scraping that sends metal filings into drains. If you keep wooden boards near the sink, learning how to fix cracked wooden cutting board can prevent crumbs and splinters from washing into the dishwasher filter or pump. And when you use non-stick pans, check their condition regularly-knowing how to tell if non stick coating is worn out helps you avoid flaking that could contaminate dishes and lead to clogs or hygiene concerns.
Final notes and realistic expectations
Many drain problems are simple: a kinked hose, a plugged air gap, or a forgotten knockout plug. Others-failed pumps, valves, or control electronics-need parts and a little mechanical work. With the right safety precautions and a stepwise approach you can often diagnose and fix the issue yourself. Keep records of parts replaced and any tests performed; that information is invaluable if you need a technician later.
More tips in the section Culinary Workspace Restoration & Flow