The central heating system in my house (a bungalow with a floored loft) has
been plumbed entirely with 15mm plastic barrier piping. While I've never
had a problem with the pipes, I wonder about the use of 15mm for the heating
loop. The loop comes from the boiler and is immediately dropped from 22mm
to 15mm and this feeds 6 radiators of varying sizes. There is also a medium
sized radiator upstairs, in the loft, which is fed directly from the boiler.
I'm about to get the boiler moved from the kitchen to an upstairs cupboard,
but wondered if I'd get better performance from the radiators if the loop
was replumbed to be 22mm all the way.

Any thoughts appreciated.

Thanks,

Murdo