I've been decorating my upstairs master bedroom for a few weks now amd
during that time the radiator has been off the wall, with the valves left in
situ on the feed pipes at floor level. On thursday the thermostatic valve
decided to open and dump water everywhere. I don't know how long it was
before it was discovered (the neighbour noticed water coming through his
ceiling!) but I was 3 hours away when I was told, and so had to get a friend
to try and stop the water. He did, and told me that the water was pouring
out of the valve itself, and not (as I assumed) the join between valve and
pipe. So I have ruined carpets downstairs, and I think the ceiling will need
The thermostatic valve had been closed (obviously!) so why did it open?
Would it have been the 'frost' protection kicking in? If so, why did it pick
the day I was away to do so, as there had been colder days the weeks
previous? Is this how the frost protection works, ie opens the valve if the
temp drops to a certain point? If so, why didn't it close again?
Or could the valve had just 'failed'?
All thoughts welcome
Could it have been that the rotary knob was actually set on "demand" but
the pin actuator had stuck down - shutting off the supply? A pretty
common occurence, IME, if the valve has been left "off" for some time in
Then the damn thing decides to pop up..
Or as above, with the pin stuck down and the top section actually not
porperly in place. So when the pin pops up, there is nothing to stop it
- even if the stat is on min.
It could have been the changes in temperature, or vibration, or change
in water pressure, or next-door playing music extra loud, or that damn
butterfly over the Indian Ocean, just caused the pin to pop out when
My thermostatic valves, on "off" wouldn't open if Hendon froze over. But
I can see why some designers might put a frost protection level in..
Come Winter time, I have to use WD40 and a pair of pliers to coax the
pin in coming out to play after the valve has been shut most of the
year. But once it starts moving, it "pops" fully open. I haven't looked
- but it may even be that the valve uses water pressure to act like a
mechanical amplifier, once it starts opening - as water solenoid valves
in washing machines do (in reverse).
Murphy rules, A OK.
I would have thought the odds were that the rotary thing wasn't fully on
"off" - but that the pin had stuck - making you think it was..
Hmmm, dunno! The knob was turned fully clockwise (past the * which I didn't
even know it had until someone mentioned it!) and it couldn't turn any
further. As I mentioned, it had happily sat there for 3 weeks in that
position without bother, and that night was no colder than any other recent
ones (several had been colder and it didn't affect it). Guess it'll remain a
mystery. I won't trust one of those valves again though, that's for sure!
Most thermostatic valves don't have an 'off' position.
The lowest they go is 'frost protection', and presumably
it got cold. Valves are usually supplied with a 'decorators
cap' which you screw on in place of the thermostatic head
if you really want to switch the valve off. It looks like
a large bottle cap.
Thanks Andrew, I didn't know that. One more cap for your collection of
It presumably may have been it didn't open earlier, when it was colder,
because the pin had been stuck? And chose that moment becuase, well,
Also, even though the outside temp was no colder than before the room may
have been getting steadily colder cos the rad had been off for such a while.
I always use the decorators cap - I just would not trust it otherwise!!
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