DIY Doctor

new combi

Postby Repo Refurb » Fri Sep 18, 2009 6:18 pm

am i right in thinking that if i put a combi boiler in my house that the flow and return pipes for the rads should be in 22mm then i can tee off to 15mm pipe to connect to the rads. Also should the hot and cold water supplys be run in 22mm from the boiler and then teed down to 15mm when i get to the taps??

last one: what litres per minute flow rate do i need from the boiler, it will srvice 8 rads and 1 bathroom aswell as the kithen.

thank you.
Repo Refurb
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Simply Build It

Postby uk_ducati » Sat Sep 19, 2009 8:28 pm


yes flow and return to be in 22. as for the cold and hot water they are fine to fit in 15 as it is a combi and will have mains pressure.

the flow rate would need to be measured with a weir gauge as you may have a high flow rate on your taps. this then could be used to give you an idea of what size boiler to be used

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