pete franklin
Not quite sure what you mean by cap the supply Philip. The water supply to the shower should have an isolating valve on it. You don't say if it is an electric shower with only a cold supply, or a mixer shower with hot and cold. Either way there should be isolating valves. if there are no valves fitted, you will need to turn off the relevant supply. This would be the cold main for an electric shower. If you have a mixer shower supplied by a combi boiler, then turning off the cold main will stop both hot and cold supplies to the shower. If you have a conventional system (cold tank in roof, hot water cylinder in airing cupboard) then the shower should have a hot supply from the cylinder and a cold supply from the tank in the loft. If this is the case look for isolating valves in the airing cupboard. I hope this helps, if not come back with more information.
