Removing Chimney Breast with back boiler and install new combi

You don’t need new piping for central heating in this case

Removing ALL the pipework- depends what you want , depends if ALL the pipework is in good condition(usually it all IS) A powerflush will 100% of the time be needed. Please note- some homes can be a ONE pipe system in this case I would recommend new pipework to a TWO pipe system so that it will properly work and be up to scratch for Boiler Plus Regulations 2018 That's if you are going to Install a combination boiler. knocking walls down is advise from a builder not a gas engineer/Plumber. pricing can vary by thousands what you want is a good job done well NOT the cheapest!!! you go for the cheapest EXPECT problems.(just an FYI)

Yes it can be done by a qualified Gas Engineer. First the Gas supply have to be dismentled safely by Gas engineer. Empty the central heating system so the heating pipe connected with the boiler can be dismentled and relocated for the new combi boiler. Make sure before the chimney duct will be removed it needs to be tested for any asbestos presence. All the structural and building work has to be done by professional building contractors(Like removing chimney and supporting the system according to structural design done by structural engineer). New Boiler can be installed with the existing pipe depending upon the system design, condition of the pipe work and the work carried out should be building control compliant and Gas safe regulations. Best advice will be to get survey done by a Gas engineer.

You wouldn’t need to completely change your pipework but would need to adapt it for a combi system. All radiator pipework would remain the same 👍🏼