10mm to 22mm heating pipes

7 May 2009
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United Kingdom
I have to tee off a 10mm pipe run from a 22mm main heating run. There is one rad to go on a dot – dabbed wall which will have the drop in 10mm plastic pipe (in conduit etc).
My concern is will it work if the 10mm just taken from a 22 tee (not manifold type) with the rest of the system using 22 and 15 pipe work.
Cheers bob.
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Probably but it will all depend on the power output of the rad and the length of 10 mm tube.

It would be safer to use 15mm until just before the wall drops if its much further on.

Yopu might have to do a little balancing if its not hot enough at first.

I was thinking of running in 15 right up to the top of the drop, as you said, then down in 10. The whole house is a total re-plumb, heating, hot and cold services which we’re doing, so can design in and accommodate this one rad on 10mm if it will work. The rad in question is in a new large extension. Ive been doing nothing but boiler changes for last 10 years so a bit rusty on the plastic front.
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But what is the heat output of this rad?

Have you calculated to arrive at that size?


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