On Sat, 01 Nov 2008 14:43:35 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
wrote:
If I ever fit a system of my dreams it will have a drain point to the
outside of the house and a dosing point (whatever one is)

18 months ago I got my CH boiler replaced and I made sure the guy
connected up the existing drain pipe to the outside down pipe and also
fitted a filling point beside the boiler for the concentrate .It's
just a branch off the pipe from the boiler which is turned upwards for
a few inches and has a compression stop on the end that you remove
when it needs refilled or topped up.

You'll still need to drain down before adding concentrate - and rather
further than if you use the highest rad in the house.
In other words, drain about a bucket full out of a sealed system. Add the
concentrate via the bleed valve on the highest rad. Then refill and with
luck only that rad or it and the others on that level will need bleeding.

I take it that reply is directed at the OP?