Question about new boiler and gas supply pipe

[mistert]

Hello there I hope one of you experts will be able to advise me on this one.

Just about to get quotes for replacing a potterton lynx 2 combi boiler, it's still going strong but we are looking to replace the whole bathroom where it's located.

I mentioned this to an engineer when I was getting it serviced last year and he mentioned that the gas supply pipe would need to be replaced with a slightly smaller width and it was something that all new boilers required.

My issue is that the supply comes in at the front of the property under the floorboards to the kitchen then goes up along the roof past the cooker and onto the bathroom to supply the boiler.

The run of pipe when it comes out from under the floor is a good 30 feet at least. My first question is can I get away with just replacing the pipe thats exposed? as this would make the whole job a lot easier especially as the boiler is still working fine. My second question would be are there any modern combi boilers availiable that would work with my eisting piping? It looks to be about 16mm wide but i'm not sure of the correct way to measure the pipe.

Thanks in advance

[Agile]

Absolute minimum gas supply pipe size is 22 mm. Longer runs will need 28 mm.

A solution is sometimes to take it round the outside of the property or through the loft.

Tony

[Henry]

he's right, condensing boilers need BIGGER pipes because they need more pressure + volume to stay efficient.

They really need 20mb working for max efficiency because the flame is so small.

[SimonD]

Really?

They need a bigger flame and more pressure to stay efficient....... do elaborate, I can't wait.