On Thu, 03 Jun 2010 10:29:10 +0100, Doctor Drivel wrote:

It protects the heat exchanger as it is on the return. It also prevents
radiators sludging up.

To sweetheart - as noted, this is the nutter I mentioned. Ignore him.
--
Use the BIG mirror service in the UK:
http://www.mirrorservice.org

*lightning protection* - a w_tom conductor