In an earlier contribution to this discussion,
Geoff Lane wrote:

I've got a Combi boiler system, three of my rads have no thermostat
fixed and I want to fix one to two of them.

Do I have to drain the entire system to do so of is there a way round
this.

Geoff Lane

You'll have to at least partially drain it - and obviously the rads
themselves.

Start with one of the rads. If there's a drain cock in the pipe next to one
of the valves, use that - with the valve open - to drain the rad and pipe in
one go. If there isn't, it gets a bit messier. Priceed as follows:

Turn off both valves tightly. Partially undo one of the unions between rad
and valve, and collect the water from the rad in a container. Undo the bleed
screw on the rad.[Use lots of old towels to protect any carpets from foul
black staining liquid.]

When the rad is empty, fully undo the union plus the one the other end - and
lift the rad off its brackets. [While it's off, take it outside and give it
a good wash out with a hosepipe].

At this stage, the pipework is still full of water - only the rad is empty.
Decide which valve you're going to replace with a TRV. Drain down the
pipework feeding that valve into a container by opening the valve. When no
nore water comes out you can remove the valve from the pipe and fit the TRV
instead.

Swap the tail in the radiator with the one which came with the TRV. [This is
most easily done with the rad lying down on a Workmate or similar]. You can
then re-hang the radiator and connect the valves to the tails.

Then do it all over again with the next rad!
--
Cheers,
Set Square
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