I recently found that my 2yr old CB28 boiler and new
central heating system never had any inhibitor chemical
added to the sealed system,the water is a bit brown. I've been
advised to clean the system and add inhibitor.
Once the cleaner has done its best, I thought I would be able to undo the
drain plug on the kitchen radiator, and
while the water pours out turn on the filling loop at the Combi boiler, thus
power flushing the entire system with
nice clean water.
Does this sound Ok or am I deluded.
You are deluded.
Your method will only result in flushing the shortest part from the fill
point to the kitchen radiator. You need to:
* turn off and drain all radiators
* remove each one in turn and take it outside and wash it out with a hose
* with the radiator out, and the filling loop connected, open each radiator
valve (with a bucket handy) and run until the water is clear
That way, you'll flush *all* the pipes *and* the radiators.
Thanks for putting me strait.
Ouch!! that sounds like a heavy duty job, maybe I could
just add inhibitor seeing as the system is only 2yrs old and
halt any further corrosion.
Or am I double deluded
Hmm, I'm not sure this is necessary (although it is probably the most
thoughrough way of doing it).
I had a similar problem - slack plumber had never flushed the system. I
added a drain valve on the return to the boiler. On my boiler, when it
is turned off, no water can flow from the fill point to the drain (i.e.
through the boiler heat exchanger). By fitting a bit of garden hose to
the drain point, closing all rads off, then opening each in turn, I
believe I was able to flush just about the entire system, without
disconnecting any rads..
It really depends on how bad it is. A system without inhibitor can
be quite full of sludge in a matter of months if the tap water is
The proposal from Mr Set Square gives the right angle on this and I
would take that trouble if the system is microbore or there is any
sign of radiators feeling cool at the centre bottom when the heating
is on. This is because sludge build up in radiators tends to be at
the centre bottom. If it finds its way into the pipework, the flow
will become a problem.
Since you're depressurising anyway, then you could do a sample of one
upstairs and one downstairs radiator and decide from there.
If it isn't bad, then John's method works well as long as you have the
service valves and can direct the flow.
You can also add a system flushing agent (Fernox and Sentinel make
them) and run the system hot for the recommended time - normally up to
a week. Then thoroughly drain and flush and add the inhibitor.
Chemical flushing agents won't clear a heavily sludged system but
will help if the problem is fairly minor.
You can get a more thorough flush without going to the lengths of
individually flushing each rad by judiciously turning off radiator valves
and service valves on your boiler to force the water to go through other
paths. You'll need to know how it's all plumbed together to figure out how
to get it to do what you want. And/or you can just run it up to full
temperature then switch off and open up the drain cock to empty it; refill
and repeat a few times.
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