The quarter-turn Bristan ceramic insert hot-water tap in the bathroom basin has had a slight drip for ages. One odd thing is that the tap lever has a bit of play in it so that it can be moved slightly to any side by a mm or so, as though the ceramic valve disc cartridge is loose. However, the cartridge is so tight I cannot undo it after removing the tap shroud, so what is loose? Unfortunately, the cold-water tap cartridge is also so tight that I cannot undo it to examine the valve construction.
According to the photo of a dismantled cartridge at 9.39 at
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(Step 4 - repair your valve), there is nothing that can be tightened. Is it possible that one of the black "O" rings has failed and broken up?
If I can't undo the cartridge (I've tried WD40), are there any options other than a new tap?