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?
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?
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...

Load of info in the SealedCH faq.
The thermo valve should really have been able to shut off and the
lock-sheild.

Which side of the valves did you loosen to remove dthe rad?

Did you add inhibitor on refilling.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html