Since having a new Boiler installed in my loft my Husband is having to top up the pressure every 2/3 weeks as the boiler and hot water are going cold. We have asked the Plumber to come back three times and he has assured us that there is nothing wrong with the Potterton Gold Boiler which he has installed but has said that if it keeps going off then there must be a leak somewhere (we never had this with the old appliance). As all our pipes are in the walls of the semi detached house how do I find out where (if any ) there is a leak please can you help as I am unable to climb into the loft when my husband is not around.