Magnaclean-Any good?

Yes, they do get a lot of the black silt out of the system. However, there is a 50% chance that the unit will fail after a year (yes, really). Google for 'leaking magnaclean', and you'll see how many have failed early. There are alternatives on the market which have a better reputation for longevity.

The Fernox TF1 is much nicer all round - can be drained in situ and also has a cyclonic trap for catching non ferrous particulates. (and its not bright red either!)

Thanks for that. They sound a bit like the heating equivalent of the Saniflo!

I had one installed in 2003, and it failed last year. The failure point was the main O ring where the body joins the cap. The failure occurred at the time the heating started to come back on in the autumn.

Adrian