I need a new boiler but getting mixed messages on the pipework. Our current combi boiler is fitted to 15mm central heating pipework. British Gas have advised that all of the pipework in the house must be changed to 22mm. Another plumber has told me that if I increase at least 4m of pipework to 22mm, then that should help to ease the flow. And the third quote, the plumber reckoned running a 22mm pipe from the boiler (approx 10cm in legth) to 15mm pipework will help. So confused - any ideas?
We are considering Worcester Bosch 30si / Viessman / Glow Worm Ultraicom 30ci.