You already have in place a mains cold supply ,you need to pipe hot from your combi which should quite close to where you are going to site the shower mixer say from the hot supply upto a washhand basin or from under a bath.Also mixer valves generally require balance water supply pressures from both hot and cold and a hot supply temp. to mixer of 55 degrees centigrade to achieve a nice blend temp of say 43 degs. c.
J.McCormack, August 2010
