Hi, apologies similar topic again. We had a brand new worcester CDi 37cdi installed in the airing cabiner upstairs. 7 new radiators and new pipework installed while changing boiler from gavity feed system. The system does not seem to hold pressure. The installed has already been twice. Lifted floor boards still not joy finding any possible leak. All The radiators are unconfortably hot to touch, is that proof that there are no leaks. No pipes in the concrete. No wet patches in the ceiling downstairs. I cannot see any water dripping out of PRV. The problem is when I pressure system to 1.5 when CH is on the pressure goes up. But over night when the CH is switched off the pressure falls. The pressure goes from 2 to 0 in 2-3 days. Could anybody please suggest what is wrong with the system. The system was installed just around 4 weeks ago and paid a fortune for getting the heating sorted. The house is warm and do get warm water, but pressure lost.