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By Stuart yaxley
Hi all my first post so be gentle
I need to add two extra radiators down stairs in separate rooms we have a two pipe system feed and return and it's like a split system where we can have upstairs radiators on but not on downstairs ,all the pipework up stairs is 22mm and the pipes that runs down the wall to downstairs radiators are 15mm and all the 15mm pipe has been hidden by the dot and dab plasterboard, can I tee off a existing downstairs radiator and add the two extra radiators so in theory there is three radiators on one spur or do i need to go back to the 22mm upstairs and give each one there own feed and return any help would be really appreciated as the pipework needs to be hid back behind the dot and dab to match the rest of the house .thanks
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hello and welcome.

that seems ok to me. just connect to exsisting rad pipe each end and daisy chain to other 2 rads.
you will need to throttle down the lockshield down on hard on first rad, then a bit less on 2nd finally on 3rd leave open.
otherwise rads wont heat up.
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By Best
Hello. Hopefully the two radiators you are going to add have not too large an output.
The combined output of the 3 rads that the existing 15mm pipes will then be feeding would need to be in my opinion ideally not much more than approx 6 kw if gravity open vent heating system, but sealed heating system (combi boiler for example) would cope with bigger demand.
Designer vertical rads really best piped individually from large pipes.
As Redsaw advised, get the system all balanced to help the rads heat properly

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