Tim+ wrote:
BG came around to my Mum's to look at her combi which wouldn't supply
hot water when the CH wasn't calling for heat.

Apparently some crud in the valve which they sorted and to their
credit, they *didn't* try and sell her a new boiler. Instead they are
pushing a system "power flush" for £600 which sounds a lot to me.

Assuming I'm prepared to spend a day messing around looking for drain
cocks and bits of hosepipe, is there any reason I can't do this
myself?

Is there a recommended flushing substance to treat the system with
prior to a full flush?

Tim

I've read that a power flush finds leaks in rads which if left alone would
not be leaking.
I'd leave well alone.