Sounds very much like what happened to my hot tap in the mixer shower tap the valve assembly with the washer on it has come adrift and is stuck over the inlet. Turn off the hot water system. If fed by hot water tank and not a combi boiler turn of the cold flow to the hot tank then run the basin hot tap to make sure it's off. If combi turn boiler off and water inlet to stop flow through boiler. Remove the tap knob [small screw under centre cap which pops out with small screwdriver down edge] . Place rag around the casing of the hot tap and remove with wrench. Now undo the tap centre piece you may find the inner piece with the washer may be still in tap body remove it. take note of type of washer [digi picture helps] and buy spare so next itme you do it renew the washer too.
Liberally coat the inside of the outer part before replacing the inner bit then wind it in and out to work the vaselene into the threads. Replace whole assmebled the centre piece complete tight but don't over do it, then body capping then tap knob. Turn to closed positon and turn water back on. Turn tap on you should have water. Bear in mind it will happen again mine did a couple of times over 4 months.
Nobby, December 2008
