Discuss Sizing my new combi boiler in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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And would I be right to say the current boiler I have would be fine running 22mm pipework.

Thanks agin for your imput.

Yes, you really need 22 with individual 15 branches to rads. I've seen boilers really badly damaged by insufficient flow, so best get it sorted sooner rather than later.
 
Yes, you really need 22 with individual 15 branches to rads. I've seen boilers really badly damaged by insufficient flow, so best get it sorted sooner rather than later.

Hi so can I still run the flow and returns to the rads off the 22mm in 15mm as the longest run will only be about 15ft and it's the 3rd rad off the boiler and about 3ft on the first floor.

Cheers
 
Yes that would be ideal. I don't tend to run any more than 3 radiators off of 15mm copper depending on rad sizes. If you start from the boiler in 22mm and pipe as far as poss in 22mm then reduce down for the last couple. You should find the extra flow will resolve your problem.
 
Cheers guys for all your advise......just one more question. Would be best if I run the main flow and return pipe in 22mm all the way to the last rad then Reduce to 15mm for the valves. Then just tap off the 22mm and connect upto my existing 15mm legs to the rest of the rads.


Cheers
 
You'll be fine with the last rad on 15 f&r. It's basically a long tail.
 
Have you flushed your cast iron rads before installing them?
 
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