A dishwasher is the one appliance most people assume cleans itself. It runs hot, it runs full of detergent, and it ends every cycle looking spotless — so the filter goes unchecked for years.
That assumption has been tested. A 2016 study published in PLOS One sampled domestic dishwashers and found the black yeast Exophiala dermatitidis and related opportunistic fungi living in the rubber door seals — an environment that combines heat, moisture, detergent and food residue in a combination that almost nothing else in the house replicates.
The practical version of that finding is simpler: if your dishwasher smells when you open it, or leaves a chalky film on glassware, the machine needs cleaning before the dishes do.
Quick Answer: Pull out the filter at the base and rinse it under hot water with a brush. Check the spray arm jets are clear. Wipe the door seal and the door lip below it. Then run an empty hot cycle with a cup of white vinegar sitting upright on the top rack. Do the filter monthly, the full clean quarterly.
The Three Things That Actually Cause the Smell
The filter. Every dishwasher has one, usually a twist-out cylinder at the base of the tub. It catches the food the spray arms wash off. Left too long, it becomes a warm, wet food trap that scents the whole cabinet. CHOICE Australia is unambiguous that a filter full of scraps and grease is behind most dishwasher complaints.
The door seal and the door lip. The spray arms never reach the flexible seal or the flat lip of the door below it. Food splashes there, sits, and grows. This is the same fold problem a front-loading washing machine has.
Hard water. In much of Australia the tap water carries enough dissolved calcium and magnesium to leave scale. The NHMRC's Australian Drinking Water Guidelines set out the hardness bands; Adelaide, Perth and parts of Brisbane sit noticeably harder than Sydney or Melbourne. Scale is what turns glassware cloudy and what slowly narrows the spray arm jets.
What You'll Need
White distilled vinegar (5% acidity) or a proprietary dishwasher cleaner
Hot water and dish soap
An old toothbrush
A microfibre cloth
A toothpick or a straightened paperclip
Rubber gloves
⚠️ Safety note: Never put dishwashing liquid in a dishwasher — it foams uncontrollably and will flood the kitchen floor. And never mix bleach with vinegar or any acidic cleaner; the Washington State Department of Health treats the resulting chlorine gas as a real household poisoning risk. Pick one product per cycle.
How to Clean a Dishwasher, Step by Step
Step 1: Empty It and Pull the Filter
With the machine empty and cool, slide out the bottom rack. The filter sits in the floor of the tub — most twist a quarter turn anticlockwise and lift straight out. Many have two parts: a coarse mesh cup and a flat fine screen beneath it.
Rinse both under hot running water, scrubbing the mesh with the toothbrush and a little dish soap. Hold the fine screen up to the light — if it isn't translucent, keep going.
Wipe out the recess the filter sat in before you put it back, and make sure it locks. A filter seated loosely lets debris straight into the pump.
How often? Monthly for a household running the machine daily. Fortnightly if you don't scrape plates thoroughly.
Step 2: Clear the Spray Arms
Most spray arms unclip or unscrew by hand — check your manual before forcing anything. Look along each arm at the jet holes. Any that are partly blocked with scale or a seed will be spraying sideways instead of where they should.
Clear each hole with a toothpick, then rinse the arm through under the tap and spin it to check it turns freely.
Step 3: Wipe the Seal, the Lip and the Dispenser
Run a cloth wrung out in hot soapy water right around the flexible door seal, getting into the fold. Then do the flat lip along the bottom edge of the door — the strip below the seal that never gets sprayed. This is usually the dirtiest part of the whole machine and the one nobody looks at.
Finish with the detergent dispenser flap and its hinge, where old powder cakes and jams the door.
If there is black spotting in the rubber rather than on it, Better Health Victoria recommends a diluted bleach solution on hard non-porous surfaces — ventilate the room, wear gloves, and rinse well afterwards.
Step 4: Run an Empty Hot Cycle
Stand a heatproof cup or bowl holding about 250 ml of white vinegar upright on the top rack. Don't pour it into the detergent dispenser — that releases it at the wrong point in the cycle.
Run the hottest, longest cycle the machine has, empty. The vinegar dissolves grease film and limescale that the filter clean can't reach.
Don't add bicarb soda in the same cycle. As Dr Nathan Kilah, Senior Lecturer in Chemistry at the University of Tasmania, explains, acid and base cancel each other out on contact — the fizzing is the reaction consuming itself, and what remains does very little. Use one or the other.
Step 5: Top Up Rinse Aid and Salt
If your machine has a separate salt reservoir — most European brands sold in Australia do — check it. Dishwasher salt regenerates the built-in water softener, and in a hard-water city an empty reservoir is the single biggest cause of cloudy glasses.
Rinse aid does a different job: it breaks water's surface tension so droplets sheet off instead of drying into spots.
What Not to Do
Don't pre-rinse the dishes. Scrape solids into the bin, then load. Modern dishwasher detergents contain enzymes that need something to work on, and many machines have a turbidity sensor that reads a spotless load as a light soil and shortens the cycle. Scraping is enough.
Don't wash sharp knives, cast iron or unsealed timber in it. Prolonged hot water and alkaline detergent blunt edges, strip seasoning, and swell timber handles.
Don't overload the top rack over the bottom. Tall items on the bottom rack block the upper spray arm, which is why one section of a load comes out dirty while the rest is fine.
Don't leave the door shut after a cycle. Crack it open for twenty minutes so the tub dries. That single habit does more against odour than any cleaning product.
How Often to Clean a Dishwasher
Task | Frequency |
|---|---|
Scrape plates before loading | Every load |
Wipe door seal and lip | Weekly |
Rinse the filter | Monthly |
Empty hot vinegar cycle | Monthly |
Clear spray arm jets | Every 3 months |
Check salt and rinse aid | Every 3 months (monthly in hard-water areas) |
Frequently Asked Questions
Q: Why does my dishwasher smell bad?
The filter, nine times out of ten. Food trapped in the mesh sits warm and wet between cycles. Pull it out and rinse it under hot water — if the smell survives that, check the door seal fold and the flat lip along the bottom of the door.
Q: Can I use vinegar to clean my dishwasher?
Yes. Stand 250 ml in an upright cup on the top rack and run an empty hot cycle. It handles grease film and limescale well. Use it monthly rather than every cycle — sustained acid exposure isn't kind to rubber seals over years.
Q: Why are my glasses cloudy after the dishwasher?
Two different causes, and they need different fixes. A white film that wipes off with vinegar is hard-water scale — top up the dishwasher salt and rinse aid. A permanent cloudiness that doesn't shift is etching, which is irreversible damage from very soft water combined with too much detergent, and the fix is less detergent on future loads.
Q: Should I rinse dishes before putting them in the dishwasher?
No — scrape, don't rinse. Detergent enzymes need soil to bind to, and many machines detect a pre-rinsed load as lightly soiled and run a shorter, cooler cycle. Scraping food into the bin gets you a better result and saves the water.
Q: How do I clean a dishwasher filter?
Twist it anticlockwise, lift it out, separate the coarse and fine parts if it has both, and scrub under hot running water with a toothbrush and dish soap. Hold the fine screen to the light to confirm it's clear before locking it back in.
Q: Do dishwasher cleaning tablets work?
They do, and they're convenient for a machine that's been neglected for years. For monthly maintenance on a machine you already look after, white vinegar does the same job for a fraction of the cost.
