Unscrew the aerator, soak it, refit it — that is the whole procedure, and it restores most taps people were about to replace. It is the first thing to try when one tap has gone weak and the others are fine.
Getting it out
Modern aerators are recessed and take a small key, usually supplied with the tap and lost within a month; keys are sold in sets for a euro or two. Older ones unscrew by hand or with pliers and a cloth to protect the chrome.
Note which way round it goes
The screen and its rubber washer come out as a stack. Photograph it before it comes apart, because a rubber washer refitted upside down restricts flow more than the scale did.
The soak
Ordinary descaler, or the household acid your maker permits, for a few hours. Then rinse thoroughly. If the mesh is torn or the plastic is cracked, replace it — the threads are standardised, M24 male and M22 female covering most European taps, with M28 on many kitchen mixers.
When it is not the aerator
If flow is weak at every outlet, or on the hot side only, the cause is upstream and the aerator is a red herring.
Questions people actually ask
How do I know which thread my aerator is?
Take the old one out and measure it, or take it to the replacement. Male and female threads of the same nominal size are different parts and look alike in a photograph.
How often should it be done?
In hard water, once a year is enough to keep a tap behaving. It is also the first diagnostic step whenever flow drops, so most people do it when they notice rather than on a schedule.
Last reviewed 5 September 2026