22mm Pipe for extension to central heating

[GH1]

Hi all,

looking to do house extension 8 rooms to 12 rooms as part of this I will be upgrading to a system boiler and installing pressurised hot water tank (megaflow style but another brand with external expansion). It has been suggested that we should upgrade the radiator pipework to 22mm for the new rads added (presumabley to increase flowrate but then pressure is less ??). (By the way I am aware that we need to upgrade incoming main my question is about the central heating)

Clearly I am not a plumber and others have questioned the need for this, can anyone explain why we might need to upgrade to 22mm, what benefits would it offer and is it necessary or just nice to have ?

Any feedback appreciated.

 

[Bahco]

You need to extend existing 22 mm to feed the extension and drop down to 15 mm for each of the rads.

You may get away with 15 mm but your rads will take longer to heat up and is better practice to come off 22mm.

Your choice.