There is a particular stage of dishwasher decline that most households live with for far too long. Plates come out with a fine grit on them. Glasses develop a dull film that no amount of polishing shifts. Open the door the morning after a cycle and there is a faint, swampy breath of yesterday's dinner. None of this means the machine is dying. It almost always means the filter is full, the spray arms are blocked, and nobody has looked at the rubber seal since the day it was installed. Twenty minutes, mostly with a washing-up brush, puts it right.
Start at the bottom: the filter
Pull out the lower rack and look at the base of the machine. You will find a cylindrical filter, usually with an arrow showing which way to twist, sitting in a flat mesh plate. Twist, lift out the cylinder, then lift out the mesh underneath it. Expect the contents to be unpleasant — softened food, a bit of grease, occasionally a bay leaf from a stew you have forgotten about.
Rinse both parts under the hot tap with washing-up liquid and a soft brush, working through the mesh from both sides until the light passes through it cleanly. An old toothbrush handles the fine screen. If there is greasy residue, let the parts soak in hot soapy water for ten minutes rather than scrubbing hard — the mesh is finer than it looks and does not enjoy being attacked. Clear any sludge out of the well they sit in with kitchen roll, then seat everything back firmly and lock the cylinder. A filter that is not clicked back in properly lets debris straight into the pump.
