The dishwasher isn't cleaning the dishes
Before you think about replacing the machine: nine out of ten 'my dishwasher is broken' cases are a filter that has never once been opened, or spray-arm holes furred up with limescale. Twenty minutes makes it work like new.
The problem
Dishes come out with food still on them, or with a white gritty film, or still wet, or the glasses are cloudy. Sometimes there's a bad smell inside, or water standing in the bottom after the cycle.
Likely causes
A blocked filter (cause number one — and most people have never opened it)
There's a filter in the bottom of the machine that catches food debris. When it clogs, the dishwasher sprays the same dirty water back over your dishes. The result: dishes that come out dirtier than they went in, plus a smell.
Spray arm holes blocked with limescale
The arm that spins and sprays has small holes in it. Scale and food debris block them, so the water never reaches some of the dishes. The tell: one side of the machine comes out clean and the other doesn't.
The salt or rinse aid has run out
White marks and a gritty film on glasses = hard water and no salt. Dishes coming out wet with dried droplets = no rinse aid. Nothing is broken — you've just run out.
Bad loading
A large plate blocking the spray arm, dishes touching each other, bowls facing the wrong way and collecting water. The machine sprays in straight lines — anything blocking the spray leaves the area behind it dirty.
Water not hot enough
A dishwasher needs hot water to melt grease. Eco and quick programmes sometimes never get hot enough for genuinely greasy dishes.
A blocked drain hose
If water is standing in the bottom after the cycle, it never drained — and the dirty water just circulated. Same logic as a washing machine.
Fix it — step by step
- Open the filter and clean itUnplug the machine. Take the lower basket out. In the floor of the machine is a cylindrical filter — twist it anticlockwise and lift it out. There's usually a flat metal mesh under it too; lift that out as well.If you've never opened this, brace yourself. That is exactly what the machine has been spraying onto your dishes.
- Wash the filter under the tapScrub the filter and mesh with an old toothbrush and dish soap under hot water. The mesh must be completely open — hold it up to the light and check.Clean the recess the filter sits in too. Grease collects there.
- Remove the spray arm and check its holesThe arm above the lower basket usually unclips or unscrews with a plastic nut. Take it off and push a toothpick or a thin wire through every hole.There's a second arm under the upper basket, and sometimes a third in the roof. Do all of them.
- Soak the arms in vinegarIf the holes are scaled up, soak the arm in hot white vinegar for an hour, then push the wire through again.Vinegar dissolves scale without attacking the plastic. Cheaper and safer than any commercial descaler.
- Refill the salt and rinse aidUnscrew the cap in the floor of the machine (under the lower basket) — that's the salt reservoir. Fill it with dishwasher salt (not table salt). Then fill the rinse-aid reservoir in the door, next to the detergent dispenser.⚠️ Table salt damages the machine's water softener. It has to be dishwasher salt — the grain size and purity are different.
- Run an empty cleaning cycle with vinegarPut a cup of white vinegar in a heatproof cup in the top basket and run the hottest programme with the machine empty. This strips grease and scale out of the internals.Once a month. It prevents about 80% of these problems before they start.
- Rethink how you load itPlates below, glasses above and upside down. Don't let dishes touch. Angle bowls so water runs off them. And most important: check the spray arm turns freely — spin it with your hand before you close the door.One big plate standing in the middle = half a machine of dirty dishes. It's the single most common mistake.
- Scrape, but don't pre-washScrape the big scraps off by hand — but don't wash the dishes before loading them. Modern detergents need something to work on.Pre-washing actually makes the results worse: the enzymes need protein and starch to bite into. Give them something to do.
Tools & parts you'll need
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When to call a professional
Call an appliance technician if: water still stands in the bottom after you've cleaned the filter (drain pump); the machine never heats the water at all (dishes come out cold and grease doesn't shift — heating element); water leaks from the door or from underneath; the machine trips the breaker; or you hear loud grinding while it runs (something jammed in the pump).
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What's the white film on my glasses?
Limescale, from hard water. The fix: fill the salt reservoir and set the water hardness in the machine's settings (it's in the manual). Plenty of people run a dishwasher for years with no salt in it at all — and blame the machine.
Should I rinse the dishes before loading them?
No — and this is counterintuitive. Scrape off the big stuff, that's all. Modern detergents contain enzymes that need protein and starch to activate against. Perfectly pre-washed dishes give the enzymes nothing to grip, and can genuinely come out worse.
The dishes come out wet and don't dry
Usually the rinse aid has run out. Rinse aid breaks the surface tension so water sheets off instead of beading. Other causes: an Eco programme (which deliberately dries less), or opening the door straight away instead of waiting fifteen minutes.
How often should I clean the filter?
Every couple of weeks with daily use. It takes five minutes. It's the only real maintenance a dishwasher needs — and it's the one thing nobody does.
There's a bad smell inside the dishwasher
Rotting food in the filter or the drain hose. Clean the filter, then run an empty cycle on the hottest programme with a cup of vinegar. If the smell survives that, the hose needs clearing.
One side comes out clean and the other doesn't
The classic sign: the spray arm is blocked by a tall item, or its holes are blocked on one side. Spin the arm with your hand — it must rotate completely freely before you start a cycle.