Hi I live in a 3rd storey flat in London. I had a boiler installed recently, a Potterton Gold HE A condensing combi. The boiler has become very very noisy on startup - the case vibrates and gives a rumbling sound. The installer came back to check it and thought perhaps that there was a fault with the gas valve, so he called Heat Team who came out as the boiler is in warranty. The engineer just left and his diagnosis is that my pressure is too low. He measured it and as the boiler fires up the pressure drops from 18 down to 8. He said the vibrating is occurring because the boiler isn't getting enough gas. He stated that I would have to replace all of the pipes into the property. The current pipes are 22mm, and the gas box is on the ground floor, so they climb 4 floors before entering the property. I don't know much about this, so I just want to check, is this a plausible scenario? I only ask because the old boiler did not have this issue (it leaked and was scaled up, but didn't have this problem), and also because I got several quotes for installations (including BG), and none of them talked about replacing these pipes. I remember one chap checking the pressure and saying it would be ok. I just want to make sure because replacing all of these pipes sounds like a huge job. What size pipe would I need then? And, would it involve getting under the floors to replace those pipes too or would the ones on the outside of the building cover it? Thanks for your time.