How to Fix a Dishwasher That Won't Drain: Troubleshooting Guide

A dishwasher that leaves standing water at the bottom is one of the most common appliance problems we hear about. The good news is that in many cases, the cause is simple and something a homeowner can fix without a technician. Here's a step-by-step troubleshooting guide.

Step 1: Check the Filter

The most common cause of a dishwasher not draining is a clogged filter. Most modern dishwashers have a cylindrical filter at the bottom of the tub. Remove it, rinse it under running water, and use a soft brush to clear any food debris. Reinstall it correctly and run a short cycle to see if the problem resolves.

Step 2: Inspect the Drain Hose

The drain hose runs from the dishwasher to either the sink drain or a garbage disposal. Check for kinks, bends, or blockages. If the hose connects to a garbage disposal, make sure the knockout plug has been removed (a common issue after a new disposal installation). The hose should loop up high under the sink before connecting down to the drain — this high loop prevents backflow.

Step 3: Check the Garbage Disposal

If your dishwasher drains into a garbage disposal, run the disposal first to clear any food buildup. A blocked disposal can prevent the dishwasher from draining.

Step 4: Inspect the Drain Pump

Remove the bottom rack and the filter assembly. Use a flashlight to look into the drain area for any broken glass, bones, or debris that may be blocking the pump impeller. Remove any obstructions carefully (use gloves). If the pump impeller turns freely and there's no blockage but the dishwasher still won't drain, the drain pump motor may need replacement.

Step 5: Check the Air Gap (If Fitted)

Some dishwasher installations include an air gap — a small chrome fitting mounted on the sink or benchtop. Remove its cap and check for buildup blocking the gap. Clean it out with a bottle brush.

Step 6: Check the Drain Solenoid (Older Models)

Older dishwashers use a solenoid-operated drain valve. If this solenoid fails, the valve won't open and water won't drain. This is a job for a technician if the previous steps haven't solved the problem.

When to Call a Technician

If you've cleaned the filter, cleared the hose, and checked the disposal and pump area and the dishwasher still won't drain, the fault is likely with the drain pump motor, control board, or solenoid. At that point it's time to weigh up the cost of repair versus replacement.

Certified Refurbished Dishwashers at Oceania Appliances

If your dishwasher is beyond repair, Oceania Appliances stocks certified refurbished dishwashers from leading brands including Bosch, Miele, Fisher & Paykel, and Samsung — all with a 3-month warranty and free delivery across Sydney. Contact us for personalised advice.