Clean before Inhibitor?

[Greg]

Need to add some inhibitor to central heating system but wanted to know whether it needs to be cleaned first. I am somewhat put off by the stories of leaks appearing when it is cleaned - could do without the drips through the ceiling (plus it's a pain to do it due to all the downstairs radiators being fed on separate loops from upstairs system)

Thanks!

[Ed Sirett]

If this is simply topping up to keep the dosage up to strength then go ahead. If you have a problem or are upgrading the heating then a thorough clean out is part of the job.

[Gav]

i agree with ed, if it is a gravity system then just pour it in header, if it is sealed then you will need to drain the system a bit

[Andy Hall]

The Fernox Superconcentrate gel inhibitor (injected using a mastic gun), now has an additional fitting in the pack to make injection easier. Previously they had a small nozzle which one would screw into a vent hole in a radiator having closed the valves and drained it a bit.

The new fitting is a male threaded and will fit into the filling loop hose after disconnecting it from the mains water end. This is much cleaner and more satisfactory. The procedure for this one is to empty enough water from the system to release the pressure, then attach the nozzle to the filling loop hose and inject the gel. The filling loop hose can now be reconnected and the system refilled. Doing that flushes any gel in the hose into the system.

[mcbrien410]

I flush my 23 year old solid fuel system every two years. Turn ALL radiators OFF except one, start upstairs. Turn pump to high speed and open boiler drain valve. Header tank should soon start trying to refill. When black water has stopped coming out of boiler drain then open next radiator and close first radiator. Wait till black water stops flowing again. Work your way around the system one radiator at a time. My leak/dump radiator which is NOT pumped has to be done individually.

Chris.