How to Clean a Dishwasher Filter Properly

By Priya — deep-clean specialist, Sydney.

I want to clear something up: there’s no such thing as a self-cleaning dishwasher. That sticker on the front of your Bosch or Miele saying “AquaSensor” or “Auto 3in1” is not a self-clean function — it’s a wash-water optimiser. Open the manual to page 18 of any Bosch, Miele, Westinghouse or Fisher & Paykel and you’ll find the line: “Clean filter monthly.” Most people have never opened the manual.

Here’s the kicker — about 80% of the dishwashers I get called to look at are not broken. They’ve just got a clogged filter, the spray arms can’t get pressure, and the owner has spent six months running them empty with cleaning tablets wondering why the glasses still come out cloudy. Twenty minutes with a toothbrush solves it.

The Aussie-specific bit: dishwashers sold here almost always have a 3-stage filter system under the bottom rack — coarse mesh, fine mesh, and a micro filter underneath both. American machines often run a single filter or a hard-food disposer instead, so the YouTube tutorials skip stages 2 and 3. The micro filter is the one nobody knows about and it’s the one that does the actual work.

What you’ll need

• An old toothbrush (medium bristle, not soft)
• Warm soapy water in the sink
• White vinegar — 500 mL
• A microfibre cloth
• Rubber gloves
• A skewer or toothpick (for the spray arm holes)
• A torch
• Optional: dishwasher cleaner (Finish Dual Action, $8 from Woolies)

Step 1: Pull the bottom rack out

Empty the dishwasher first. Slide the bottom rack out completely and put it on the kitchen floor. You should now be looking down at the sump area — a circular or rectangular recess in the middle of the dishwasher floor with the lower spray arm sitting over it.

Step 2: Lift off the lower spray arm

On Bosch and Miele the lower spray arm just lifts straight up — no tools. On Westinghouse and some Fisher & Paykel models there’s a centre nut you twist anti-clockwise. Pull the arm out and look at the underside. The little jet holes are usually half-blocked with food debris, hard-water scale, or in older units, calcified gunk that looks like grey toothpaste.

Run the spray arm under hot water and use the toothpick to clear every single jet hole. There are usually 12–18 holes. If even three are blocked you’ve lost 25% of your wash pressure.

Step 3: Remove the coarse filter (Stage 1)

This is the big plastic mesh basket sitting in the sump. On most machines you twist it 90 degrees anti-clockwise and lift straight up. This is the filter people clean — the obvious one. Tip out the food chunks (you’ll find olive pits, prawn shells, chicken bone fragments) into the bin, not the sink, and rinse it under the tap.

Step 4: Lift out the fine filter (Stage 2)

Underneath the coarse mesh you’ll see a flatter, finer mesh — sometimes square, sometimes round. This is where the 80% of “broken dishwasher” callouts live. Lift it out gently. It’s usually coated in a beige slime that smells faintly of old fish even if you’ve never washed seafood.

Soak it in hot soapy water for 5 minutes, then scrub both sides with the toothbrush. Don’t use steel wool — you’ll damage the mesh weave.

Step 5: Now find the micro filter (Stage 3)

This is the one nobody knows about. Look down into the sump where the fine filter just came from. There’s a flat, matte plastic disc — usually circular, sometimes with a small tab. That’s the micro filter. On Bosch you twist it anti-clockwise; on Miele you pull a small lever; on Westinghouse it just lifts out.

Whatever’s stuck on this filter is the reason your glasses are cloudy and your wineglass stems have a film. It captures particles down to 0.04 mm. Scrub it gently with the toothbrush — bristles can damage the mesh if you go hard.

Step 6: Clean the sump itself

With all three filters out, use the torch to look into the bare sump. Wearing gloves, scoop out any sediment with your fingers and a paper towel. There’s often a small impeller visible — don’t force it, but do clear any food debris caught around it.

Wipe the sump walls with a vinegar-soaked microfibre cloth. Hard-water scale will come off with vinegar; chlorine cleaners will eat the rubber sump gasket so don’t use them.

Step 7: Check the upper spray arm too

Most people forget the upper spray arm. It twists off the underside of the top rack — usually a quarter-turn. The jet holes here are even smaller and they get blocked first because they fire downwards and gravity is involved. Skewer every hole.

Step 8: Reassemble in correct order

Micro filter first, then fine filter, then coarse filter twisted to lock. Then both spray arms. If you put the coarse filter in unlocked, the next wash will spray food everywhere and you’ll be doing this all again on Wednesday.

Step 9: Run a vinegar maintenance cycle

Empty machine. Put a heatproof cup with 250 mL of white vinegar on the top rack, upright. Run the hottest cycle — Auto 70°C on Bosch, Sani-Rinse on Westinghouse, Intensive 75°C on Miele. The vinegar descales the heating element and the spray arms from the inside.

Don’t use vinegar more often than monthly — it’ll eat the rubber door seal over years. Once a month is fine.

Step 10: Set a monthly reminder

Same day every month. The job takes 15 minutes once you’ve done it twice. If your dishes start coming out gritty before the next clean is due, your filter is full — clean it early. Households that put through a lot of rice, pasta, or oats clog filters faster.

The Priya rule

Before you call a technician for a dishwasher, pull all three filters and time how long it took. If you found grey slime on the micro filter, that was your problem. A service callout is $180–220 in Sydney; a toothbrush is $3 from Coles. The micro filter is the one to remember — coarse and fine you’ll figure out, but the micro hides under both and it’s where the real grime is.

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