Fitting Extra Radiator...Tee-off two pipes?

[WabbitPoo]

I wish to add another rad in the lounge. I have located the two pipes running to the existing radiator but I can't get to the 22mm pipes from which those are teed (the connections lie somewhere I don't wish to try to get to if I don't really have to!)

The two pipes to the existing rad are 15mm plastic.

Is it OK to tee off these two pipes to go to the new radiator? I can't see why not but then, I'm not a plumber!

Thanks

 

[Madrab]

Depends on the size of the radiators and the size of the pipes going to the current radiator.

 

[WabbitPoo]

Depends on the size of the radiators and the size of the pipes going to the current radiator.

pipes to the existing rad are 15mm plastic......I'd like to run 10mm to the new rad, but could run 15mm for some of the new run to the new rad.

 

[motorbiking]

It should be fine if they are 15mm pipes. Just try to avoid creating humps for air to get stuck in.

Don't the plastic pipes convert to copper for the visible part of the pipework?

 

[Madrab]

Again, it's down to size of the rads but unless you are going huge then that would happily satisfy most reasonably sized rads. I'd keep it all 15mm though if you can

 

[dal5band]

A 22mm pipe has cross section area of appx 380 sq mm. A 15mm pipe has a cross section of appx 176 sq mm - that is just under half. Since 22mm can run a whole house of 15 rads, the15mm will easily supply two rads. Please check my maths - cross section is pie X r X r.

 

[motorbiking]

An alternative may be to upgrade the existing radiator or check that your boiler is pushing the flow out at a decent temperature or that all your internal pipes are insulated where possible.

 

[John D v2.0]

A 22mm pipe has cross section area of appx 380 sq mm. A 15mm pipe has a cross section of appx 176 sq mm - that is just under half. Since 22mm can run a whole house of 15 rads, the15mm will easily supply two rads. Please check my maths - cross section is pie X r X r.

True and i like the scientific answer, but remember the thickness of the pipe walls, plastic pipe is very thick and the 15mm is the external diameter.
However i do agree 15mm is fine for 2 rads, my concern would be head loss not water velocity though, the perimeter to area ratio of 15mm pipe is not as good as 22mm pipe, and the usual problem people have teeing off other rads is an inability to balance the system due to excessive headloss.