On 1 Sep 2003 07:13:08 -0700, (Adam) wrote:

Hi All,

Had to take a radiator off to strip wall paper and paint behind it, so
I tackled that over the weekend. I made the mistake of not checking
uk.d-i-y before I started as there was an entry in our Collins DIY
book (thanks to whoever made the recommendation on the FAQ site, by
the way) on how to remove radiators, so I thought we'd be OK (and we
do not yet have a working computer at home, so no access to usenet at
weekends).

Everything looked good until I realised that they had no information
on how to remove radiators with thermostats on, and that they did not
cover pressurised systems. Oh well, I broke out the boiler manual and
had a good read. It all seemed pretty simple, so I closed the
lockshield (?) valve, set the thermostat to 0 and started undoing.
Several bucketfuls of water later I appeared to have drained the
entire system, which was now showing zero pressure.

We removed the radiator, worked behind it and refitted it. Then I
reconnected the radiator, reopened the lockshield valve (by the same
number of turns it had taken to close it), went up to the boiler and
opened the valve that appeared to supply mains water to the system
(via a flexible hose). Got the pressure back up and then went round
venting all the radiators. I expected to find them all still full
(all the vent valves had been closed) but all bar one on the upper
floor and one on the lower floor were empty. Having vented them, I
reopened the valve to allow mains water in and brought the pressure
back to just under 1.5 bar (as recommended in the manual).

The system now appears to be working OK, but I have some questions:
First, have I omitted anything or is the system good to go?

As long as the radiators are filled and the system is maintaining
pressure then you should be OK.

There was a certain amount (but not much) of black sludge, and the
Collins book suggests using an anti-corrosion aid in the water - how
can I get that into a pressurised system? Is it necessary?

Absolutely. It is the best £20 insurance policy you can buy. The
black sludge is corrosion of the radiators, which left unchecked will
lead to their demise. In extreme cases this can be a small number of
years.

Before you add inhibitor, you may feel it appropriate to drain the
system and clean all the radiators. I've made some previous posts on
how to do that and flush at each radiator.

You could also use a chemical flushing agent, but this will not remove
significant sludge. If the system is running OK, you could just do
that.

For sealed systems, Fernox and others make gel compounds (there's a
cleaner and an inhibitor) that can be injected into a radiator using a
tube (provided) and a mastic gun.

However, I do not recommend the maker's instructions on this which is
to inject with water in the radiator and against the pressure. It can
be messy. I found that a better way is to drain a radiator as you
did and squirt the stuff in before refilling.



Several people have mentioned that you can lock a thermostat valve
closed using a suitable 'service cap' - where can I get one and how do
I remove the thermostat body?
Lastly, if I want to intentionally drain the system, I guess I'll need
to find the draincock. Further, I guess this will be at (or level
with) the lowest point in the system. I can't find it anywhere on the
lower floor, though - any suggestions as to where I could find it?

Thanks again for all the help so far!

Cheers - Adam...

..andy

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