The short answer
A traditional tap needs a new washer, which costs pence. A modern lever mixer needs a new ceramic cartridge. Turn the water off first and put the plug in the sink.
- Turn off the water at the isolating valve under the sink, or at the stopcock.
- Put the plug in. Small screws disappear down open drains.
- Open the tap to drain the remaining water.
- For a traditional tap: prise off the cap, undo the screw, lift off the handle, undo the headgear with a spanner and replace the rubber washer at the bottom.
- For a lever mixer: you are replacing a ceramic cartridge instead. Take the old one to the merchant rather than guessing, because there are dozens of sizes.
What will ruin it
A tap that drips from the spout is a washer or cartridge. A tap that leaks from around the base of the spout when running is an O-ring, and a tap that leaks underneath in the cupboard is a connection, which is a different and more urgent job.
Why it works
A washer is a soft seat that a hard surface presses into. It wears, hardens and stops sealing, which is exactly what it is designed to do as the sacrificial part.
Gas work requires Gas Safe registration by law and most electrical work is notifiable. Where a tip says to call somebody, that is the advice. Full disclaimer.
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