I need to fit thermostatic room temperature control valves to the radiators
in living room and bedrooms - are they an easy DIY project? The hal and
bathroom will be the only rooms not to have them (the bathroom one is always
on anyway as long as the water is being heated)
I assume I will have to drain the CH system are there unexpected problems in
doing that? (mine system is about 30years old with boiler replaced about 10
years ago - it was drained then)
What are the best radiator valves to buy - there's heaps of them about at
all manner of prices!
Thanks in advance
Easy is a relative word. If you're a reasonable DIY person the answer is
And yes you'll need to drain the central heating system. I presume you'll
know where your drain tap is?
When I've changed radiator valves before I used the following procedures
1. Switch off the power to your central heating system
2. Turn off any water supply to the combi. The last house we had the filler
loop was permanently connected by the previous owner because the non-return
valve was faulty which meant it leaked so they connected the pipe up
permanently. This is not allowed (legal) as it can allow cross contamination
with you central heating water and your colds water supply. Yuk!
3. Is the drain valve located outside or inside next to a radiator valve? If
the latter then you may need to connect a bit of hose to the drain and feed
the hose outside.
4. WARNING. If the system is 30 years old and 10 years since the last time
it was drained you'll more than likely find the water black and slimy ....
even if you had something like furnox in the system it'll still be a bit
black and slimy so make sure it's going to drain somewhere safe.Place a bowl
under each radiator valve (as you work on the radiators) and have some
kitchen roll handy.
5.After a few minutes you can start unscrewing the bleed valves on the
radiators. Starting at the top of the house and work your way downstairs
after several more minutes.
6. Once you've drained the system you can start changing the radiator
7. In my experience it's worth flushing the radiators before fitting the
valves to get any sludge out of them. Ideally you could have the whole
system flushed by a specialist plumber but it's costly. Again start at the
top of the house. Turn off the radiator at both ends and then undue the
bottom off each radiator valve from the in/out pipes. You can then lift the
radiator off the mounting brackets and hopefully little, if any, sludge will
escape from the radiator.
8. Carry the radiator outside (CAREFUL. THE LAST THING YOU WANT IS BLACK
SLIMY SLUDGE DRIPPING ON YOUR CARPET) and then completely unscrew both
valves and then insert a garden hose into one end and flush until the water
is clear. Once the water is running clear it's worth putting the house into
the other end and again flush until clear.
9. Apply PTFE around the threads of the thermostatic valve and the control
valve (you can reuse the original control valve - sometimes you can get both
valves as a set)
10. Before putting your radiator back consider fitting reflective insulation
on the wall behind where the radiator is sited (ideal opportunity not to be
11. Re-hang the radiator and apply PTFE to the threads before connecting to
the central heating pipes.
12. Repeat as necessary.
13. Close the central heating drain valve.
14. Screw in the bleed valves on all radiators before starting to refill
.... saves finding out later you've forgotten one and the carpet's soaked!
15. Open the valves on all the radiators (control valve closed at 7 and make
sure the thermostatic valve is open)
16. Pour in central heating protection, furnox, or similar.
17. Connect the filler loop upto the central heating system and turn the
water supply on.
18. Refilling will take some time so it's worth just going around each
radiator and double checking everything whilst this is taking place.
19. Once the system has started to fill and the pressure starts to increase
you can start bleeding the system (via the bleed valves) whilst it is still
been filled. Start at the lowest radiator and bleed until all air is
expelled. Then work around the house going higher until all radiators are
bled and the system is full filled.
20. Turn off the water supply and disconnect the filler loop.
21. Turn on the cold water supply for the hot water and turn on the power to
the central heating system
22. Switch the central heating on. Note. Each time I've done the above the
system has always made a lot of bubbling and gurgling noises for a few
seconds. This is normal as air will be trapped somewhere in the system.and
you may need to bleed the radiators afterwards ... just follow the above
A useful website for balancing your radiators is
Try B&Q for your valves .... there's a sale on at the moment and they've
got some Thermostatic valves for around ?4 each.
"Ron O'Brien @ntlworld.com>" <castcall<remove> wrote in message
My dear wife has just asked me to point out that the reason I know about the
black slimy sludge from the radiator is because the first time I touched a
radiator I didn't know about the potential of any sludge and managed to tip
the contents all over the living room carpet and settee and did a rather
successful re-enactment of the Exxon Valdez Oil Spill - so be careful. If
you turn the valves full off before moving the radiator you should be ok but
look out for one or two droplets ... a small freezer bag over each valve
should catch anything until you've flushed it clear.
Ps. Thank you for reminding me of that wife ... me and teddy will be
sleeping in the cardboard box tonight !
<fx on> sound of stamping feet disappearing into the distance <fx off>
First time I removed radiators, I closed both valves so that they didn't
have to be emptied. It was December, the house was unheated for some
reason, and TRVs don't stay shut at that temperature! Fortunately there
weren't any carpets down.
My current TRVs have a shut-off setting - very useful as I have a combi
boiler, so there's not much water to drain out.
BTW, I fitted Pegler TRVs; at the time there was a 5-year warranty, they're
bi-directional and also not too expensive:
Another point to watch: the bodies of the TRVs might not fit on to the
existing pipes. With mine, the copper tails were too short after the olive,
so that had to be removed without damaging the pipe. I've had this twice,
the first time was on pipes set in to concrete floors (too long, but I
didn't want to shorten them by even 5mm as another valve in the future
might need the length), so the pipes were sacrosanct! The is probably an
'approved' way of removing the olives, but I did it this way:
junior hacksaw, cut diagonally across the olive (this avoids cutting in to
stop cutting before getting to the pipe!
use a suitable screwdriver and twist the olive open.
You don't understand Newton's Third Law of Motion?
You can buy a purpose made tool for removing olives ... a bit expensive if
you're only doing one but ideal if you've having to remove a few or if it's
a little tight to get in there with your junior hacksaw ... you can save a
lot of time with it.
(Amazon.com product link shortened)
Screwfix has a tool for the job:
a quid more and, by the look of it, might affect the end of the pipe (it
looks as if it pulls the olive off and I've seen pipes where the olive wall
well embedded). The Amazon one looks better.
You don't understand Newton's Third Law of Motion?
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