Locating the washer
Close off the water supply to the tap and open the tap to drain excess water. Put the plug in the waste outlet - not to stop loss of water, but to safeguard against losing any of the tap components when dismantling it.
Remove the top cover of the tap. This may be a metal type with a hexagonal base, in which case you should wrap some cloth around it before undoing with a spanner. The cloth will prevent it being scratched. Hold the tap itself to prevent it turning.
Some taps have a moulded plastic cover held in place with a small screw located in its top (sometimes under a plastic insert, which will need to be gently prised out with a thin bladed screwdriver).
Undoing the tap
Once the cover is removed, undo the top section of the tap by turning the hexagonal nut next to the base with a spanner. Hold the tap itself (wrapped in a rag) using a pipe wrench to prevent it turning.
Lift the top section out of the tap.
Replacing the washer
On the underside of this will be the washer retained by a small nut, which should be undone, or a button.
Remove the old washer and replace with a new one. Make sure that pieces of the old washer are not left in the seat of the tap before finally reassembling it and switching the water back on.
Reverse pressure tap
This is a rather old form of tap but it is quite possible to change its washer if needs be using readily available replacements. A valve inside the tap enables the washer may be replaced without the need to switch off the water supply.
Wrap a cloth around the hexagonal nut above the nozzle and hold it with a spanner. Unscrew the nozzle with the other hand.
Tap (no pun intended) the nozzle on a block of wood to free the finned section inside. Remove and replace the combined washer jumper.
Reassemble the tap and test.
Mixer tap spout
If leakage occurs from the base of the spout, the likely cause is a worn seal. Turn off both taps but not the main supply to them.
Unscrew or lift up the retaining shroud.
Lift the spout up carefully.
On some models, the spout is held in place with a retaining screw, which should be undone.
Remove and replace the worn seal, which is usually an "O" ring type – like a little rubber ring sitting in the groove on the assembly.
Be sure not to damage or stretch the "O" ring when refitting your spout. A little silicone lubricant may be used to ease reassembly.
Mixer tap valves
Modern mixer tap valves now have "O" rings in place of the old gland packing.
To replace these, turn off the water supply to both hot and cold, remove the cover piece and the circlip holding the stem in place. To do this, place the blade of a screwdriver between the ends of the clip and twist – be prepared to catch the clip. Once released, it has an extraordinary ability to vanish!
Undo the mechanism and remove the assembly. Remove and replace the "O" rings. Take care not to damage them. A little silicone lubricant may be used to ease reassembly.