In article ,
"Allan Gamble" writes:
Can I add another radiator on my system. Is it possible to tee off from the
feed pipe off an existing radiator, one from the feed line and the other on
the return or will this cause problems?

That would normally be OK, unless either radiator is extremely big
in which case the pipework might not handle the flow for another.
You should rebalance the radiators afterwards.

If your system is a single pipe system (radiators connected in series
rather than parallel), then you would connect it in series, with a
bypass pipe across the bottom, as with the other radiators. Then
rebalance that single pipe loop.

--
Andrew Gabriel