"Andy Turnbull" no email please! wrote in message
...
Thanks for your reply,

I had to re-hang one of the radiators the other day so emptied it first
and
the water that came out was clear apart from the very end when some black
goo seeped out.

The CH system is about 4 years old, so is this normal.

Thanks,

Andy

Normal for a system without corrosion inhibitor, I would say.

The sludge is almost certainly the result of corrosion.
With fully functioning there (allegedly) shouldn't be any.
Doesn't sound to bad at the moment but a flush out with a flushing compound
followed by a treatment with corrosion inhibitor should improve the long
term prospects of your system.

HTH
Dave R