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.