Added new rad, but can't get it hot

[Jimster]

I should say I'm not a plumber,
I added a rad into my friends house for him, (he has a modern combi boiler) as the rad I was adding to his downstairs loo was only small (around 500mm wide) I took the feed for the rad off another rad in the next room. As the pipes where 15mm I thought there would be enough flow to heat both rads. I simply put a T in the flow and the return pipes going to the old rad, and ran them to the new rad.

I'm having problems getting both rads hot. If I turn one rad off, the other comes on, and visa vera, but if I leave both on, only one gets hot.

What have I done wrong?

 

[oilman]

Have you balanced the radiators? This may apply to all ofthe radiators in the house if it was not done when the system was installed.

 

[Jimster]

no I havn't, how do I do this? never done it before.
Cheers
Jim

 

[masona]

See this.