How to Fix a Dishwasher Not Draining: Step-by-Step Guide
A dishwasher that won't drain is one of the most common dishwasher faults Australian homeowners encounter. The good news is that in many cases the fix is straightforward and doesn't require a technician. This guide walks through the causes and fixes in order from simplest to most complex, so you can resolve the issue as quickly as possible.
Safety First
Before doing anything, turn off the dishwasher and disconnect the power at the wall. If there's standing water in the dishwasher, have towels ready and a bucket or shallow tray to collect the water when you open the door.
Step 1: Check the Most Common Causes First
1. The Drain Hose is Kinked or Blocked
The drain hose runs from the dishwasher pump, behind the kickboard, to the drain connection under your sink. Pull the dishwasher out slightly (or access through the kickboard) and check that the drain hose isn't kinked or pinched. A kink anywhere in the run will prevent proper drainage. Straighten any kinks and run a test cycle.
2. The Sink Drain or Air Gap is Blocked
The dishwasher drains into your sink's plumbing. If the sink drain is partially or fully blocked, water cannot drain from the dishwasher. Run the sink and check it drains freely. If there's an air gap fitting on your benchtop (a small cylindrical fitting near the tap), remove the cover and check it's not clogged with debris.
3. The Dishwasher Filter is Blocked
This is the most common cause of poor drainage. All modern dishwashers have a filter at the bottom of the tub that needs regular cleaning. A clogged filter restricts water flow and can prevent full drainage.
How to clean the filter:
- Remove the bottom rack
- Locate the filter at the bottom of the dishwasher tub (usually a cylindrical filter plus a flat mesh filter plate)
- Turn the cylindrical filter anti-clockwise and lift it out
- Lift the flat mesh plate out as well
- Rinse both under warm running water, using a soft brush to remove any grease or food debris
- Soak in warm soapy water for 10 minutes if heavily soiled
- Refit both filter components and run a test cycle
4. The Drain Pump is Blocked
If the filter is clean but water still won't drain, food debris or a small piece of broken glass or crockery may have passed the filter and lodged in the drain pump impeller. With the dishwasher unplugged and water bailed out:
- Remove the filter as above
- Look down into the drain pump opening at the bottom of the tub
- Use your fingers or needle-nose pliers to feel for and remove any debris blocking the impeller
- Try to rotate the impeller manually — it should spin freely
- Refit the filter, restore power and run a test cycle
Step 2: Intermediate Checks
5. Check the Drain Hose Connection at the Pump
Under the dishwasher (accessible by pulling the unit out or removing the kickboard), check that the drain hose is firmly connected to the pump outlet and hasn't worked loose. Also check the connection at the sink waste end. A loose connection can cause incomplete drainage.
6. Check That the Drain Hose Has a High Loop
The drain hose should be looped up to near benchtop height before it goes back down to the sink drain. Without this high loop, dirty water from the sink can siphon back into the dishwasher. If the hose runs directly down without a high loop, attach it to the underside of the bench with a cable tie or hose clip.
Step 3: When to Call a Technician
If you've checked all of the above and the dishwasher still won't drain, the most likely remaining causes are:
- Failed drain pump: The pump motor has burnt out. This requires a part replacement and is best left to a technician.
- Faulty drain solenoid valve: On some models, an electrically-operated valve controls drainage. If the valve fails, the dishwasher won't drain regardless of pump condition.
- Control board fault: If the control board isn't signalling the drain pump to run, no drain pump will operate correctly.
Dishwasher Maintenance to Prevent Drainage Issues
- Clean the filter every 2–4 weeks depending on usage
- Run a Tub Clean or dishwasher cleaner tablet monthly
- Scrape (don't rinse) plates before loading to reduce filter clogging
- Check and clean the spray arm holes every 3 months
Need a Replacement Dishwasher in Sydney?
If your dishwasher repair cost exceeds the appliance's value, it may be time to replace it. Oceania Appliances stocks brand new and quality-refurbished dishwashers in Sydney, all with warranty and free delivery. Visit our Wetherill Park showroom at 2/14 Centre Place (open 7 days, 10am–8pm), call or WhatsApp 0422 489 492, or email support@oceaniaappliances.com.au.