Hi All,

A query re central heating long term maintenance. I replaced mine in its
entirety about 10 years ago - it's a sealed system with new rads, mostly
plastic pipework, and a new boiler about a year after that. It's had Fernox
F1 added at the recommended concentration from the start, supplemented when
needed, and has a magnetic filter on the return to the boiler - which
doesn't collect much of anything. When I've needed to remove a rad the water
is clear, and there is usually only a small amount of what looks like black
iron oxide particles in the very bottom of the radiator.

My query is - do I just continue with an occasional extra bit of F1 added,
or after ten years is it a good idea to drain, wash through with clean
water, and refill with new F1?

Thanks,

Charles F