There is a particular moment of betrayal when you open the dishwasher, reach for a glass, and find it coated in a dull grey film. Everything in there has technically been washed. Nothing in there looks clean. Add a faint sour smell when you open the door first thing in the morning and you have the classic symptoms of a machine that has been quietly working for months without anyone returning the favour.
The good news is that a dishwasher is one of the easiest appliances in the house to rescue, because almost all of its problems live in three places you can reach with your hands and a cloth. You do not need specialist kit, and you do not need to take a Saturday off. Twenty minutes, mostly standing still, and the difference shows on the very next load.
Start with the filter, because that is where the smell lives
At the base of the drum, under the lower spray arm, there is a cylindrical filter that usually twists out with a quarter turn. Pull it up and you will find the answer to the smell question: softened food debris, the odd olive stone, a layer of grey sludge. Rinse it under a hot tap, then work a washing-up brush into the mesh with a drop of detergent until the water runs through freely rather than pooling on top.
Underneath the filter there is often a shallow sump with a little standing water. Scoop out anything solid with a piece of kitchen roll, then wipe round the well. While the filter is out, look for broken glass or a stray cherry tomato — those are the things that quietly block the drain and leave a puddle in the bottom of the machine that everyone assumes is normal. It is not normal.
Put the filter back and make sure it locks. A filter left loose lets debris straight into the pump, which is a more expensive problem than a cloudy glass.
