Heya, I am in the process of getting a new boiler, and have had two different companies say different things about the regs for gas pipe size into the boiler. First company have said it needs to be 22mm to meet new regulations. The second company have said that has long as the flow rate is sufficient (once they have installed and tested it), the current 15mm (I think?) going into it will be fine (there is 22mm into the house, but where that ends we do not yet know, it could be under the floor below the boiler). Its a small flat (9 radiators) and no other gas appliances. The second company have suggested a glow worm boiler that requires less gas flow than other models. Whilst I am keen not to have to rip up things to lay in a new gas pipe, I don't want this to cause me problems down the line with getting gas safe certificates / selling the property on. Any advice greatly appreciated! Thanks!