Hello,

Does anyone have any advice on the best way of getting magnetite out
of the secondary heat exchanger of my combi? I've just tried to
descale it on the assumption that its erratic performance was being
caused by limescale on the secondary side. Howerver, from what I can
see it's actually the primary side that's clogged up with black
magnetite flakes.

Is it possible to chemically dissolve magnetite? Or is it a case of
chucking it out and getting a new heat exchanger?

Incidentally, I'm a bit baffled - the system does have corrosion
inhibitor in it, and when I drained off a gallon or so of water from
the draining cock to depressurise the system the water was virtually
clear. The magnetite seems to be quite selective.

Cheers!

Martin

I should add that a couple of hours with a bucket of steaming Fernox
DS3 descaler, a disposable drill pump for circulating the stuff, and a
lot of flushing under the kitchen tap has not made it work any
better.

On the plus side, I have learnt

a) to make sure that none of the O rings have dropped off the heat
exchanger before you turn the water back on (best shower I've got out
of that boiler in ages) and

b) that vital screws dropped inside the boiler casing gravitate to the
most inaccessible and invisible location, and that such screws are
always made of some mysterious non-ferrous metal making the use of
magnets entirely pointless.