Hi all, I've currently got 22mm running to my bathrooms (2 showers)/ kitchen; and there is a 28mm feed into the building but it reduces down to 15mm in between. Is there any benefit to swapping out the 15mm to 22mm? Am i constrained to the flow rate of the 15mm for everything past it? Or is it all fine? Everything is running off a combi boiler. Thank you. Kev
Your combi delivers hot water from a 15 mm outlet ,there would be no point having anything after that in 22 mm ,in fact 22mm will just hold more water , invariably cooled , that needs to be displaced before hot reaches outlets,taps / showers. Similarly anything after 15 mm on cold mains is pointless being larger diameter.