On 2008-05-27 20:46:22 +0100, Mark said:

Hi,

I have just removed a radiator & noted that a small amount of black
water came out (which later settled out into brown sand-like grains).

The majority of the system is fairly new (all radiators and boiler)
but there is some old pipework. The boiler is a W-B combi (i.e.
sealed). There are no leaks in the system.

I see that there are a huge number of chemical cleaner products and
inhibitors. How can I tell which would be most suitable for my
system?

TIA, Mark.

The first thing is that you need to thorughly flush out the sludge and solids.

There are two reasonable ways to do that:

- Drain system, remove radiators, take them outside and flush them with
a mains hose or pressure washer. Flush water out at each radiator
position.

- Power flush the system. This can be done by paying someone N x
hundred ££s or by renting the equipment and DIYing it.

Afterwards, use a flushing agent manufactured either by Fernox or
Sentinel. Run hot for the period recommended by the manufacturers.

Flush with plain water and finally add a corrosion inhibitor
manufactured by one of the above.

Tests made by various people here have shown that these products do
perform better than cheap generics from various places.