Depends on where actually the leak is and how easy it is to get to. If its around a soldered joint best thing to fit if possible is a service valve as far away as possible from the shower pipe at least then with a screw driver you can shut the water off rather than shutting off the mains. You will have to shut off the mains anyway as there will be some cutting involved but once in place this will then allow you to fix the pipe with the leak. If on a join you will have to remove the old joint and resolder a new one. If you are not too good at soldering or have never done it you can buy a compression joint instead which are available in all sorts of sizes 15mm 22mm etc. But again there is some cutting involved but no solder. If in doubt consult a qualified plumber. If you are confident you can repair it have a good search around the internet there is lots of tips and advice on soldering copper pipes and jointing. Good Luck
