In article , Kevin
writes
I have a spare radiator after fitting a towel rail type in the bathroom so I
am going to fit it in the living room to give a boost on very cold days. If
I put T pieces into the flow and return in the hall way it would mean a long
run, about 25 feet, to the rad. Or I could divert the flow & return to run
closer to the rad then put connections into the rad.
Would it matter if there was a very long run off the flow and return to the
rad. This will be run under the floor and I intend to insulate the pipesto
cut down heat losses.

Sounds fine, you'll be balancing the old and new rads via their lockshield
valves so any drag on the long pipe run will be compensated for. 15mm
plastic pipe would be ideal.
--
fred
Plusnet - I hope you like vanilla