Yes you do have a leak somewhere. Look at all visible joints to start with and look at pressure relief valve outlet outside(pipe coming thruogh the wall. Pull back yhe insulation to check.) If you see drips or film of water you have a problem with the valve seal/seating. possibly a build up of lime . Not a job for a novice. Regarding the possible leaks wrap kitchen roll or similar round joints and valves and see if they get damp, and look for damp spots on walls and ceilings for a clue as to where the laek might be but bear in mind that the water can run along the pipes before it drops off giving a false indication of leak site. Hope you find it without having to lift carpets and floor boards. GOOD LUCK
John Mantova, March 2012
