Faulty Thermostatic radiator valve

[Peter James]

<font color="#d6d6d6">A thermostatic valve on the radiator in the spare room appears to have failed.</font>

It will turn without any resistance, and the radiator will not warm up. The other radiators in the system are working OK. Unfortunately the spare room is where the computer is, and I spend up to three or fours hours a day in that room.

Other than calling in my local plumber, what are my options? Is it possible for an unsilled person to change the valve without having to drain down the system? Peter-- The email shown is false. If you need to contact me then try peterATpfjamesDOTcoDOTuk

Addresses are given to us to conceal our whereabouts. Saki (H.H.Munro) 1870 - 1916

[David]

Try thew following

Remove the thermostat head.

On the top of the actual valve that goes into the radiator there is a pin which after a period of non-use tends to get stuck down keeping the valve closed.

With a pair of pliers pull up the pin. Hot water should then flow.

[RJH]

I've just freed a closed valve by gently pulling the pin (exposed when you take off the valve control) upwards with a pair of pliers. It's now open - but stuck open, ho hum.

So it probably needs replacing. I have, once, replaced a valve by closing off all the radiators except the culprit, taking the pressure out of the system from the radiator's bleed valve, put down plenty of towels, then swap over - quickly.

That was a downstairs rad, and very little water came out, less than half a cup. But it was made slightly easier as one end was push fit. That said, I'll leave the current faulty valve alone until this cold spell eases up a bit.

Cheers, Rob, Sheffield UK

[alan_m]

The gotcha may be the age of the valves. When I replaced some thermostatic valves where the old ones had been installed perhaps 25 years before I found the new valve bodies to be a different length. I had to modify the length of the pipe coming out of the floor (suspended wooden flooring).

I agree that the first point of call is to remove the thermostatic head and gently pull up the pin found on top of the valve.

Example

[Martin Brown]

The simplest ones are typically a thermostatic plunger screwed on top of an actual valve and they will separate - read the manual for the particular model of valve. Left in the off position they often bind over the summer and this can be freed with a gentle tap on the plunger.

Worth seeing if the valve can be persuaded to work again first. But generally there is no way to change a radiator valve that doesn't involve draining down the system unless there are a lot of isolating valves in it. (I have never seen such a configuration myself)

[John Rumm]

There are ways and means - none are ideal, but a full drain down is not usually required for just a rad valve:

[alan_m]

There are various youtube videos showing the techniques but in my experience things don't always go a smoothly as demonstrated. When things go wrong there is a lot of (dirty) water that that can come out of a single disconnected pipe. When water starts flowing most people would panic :)

When I last did something live on my central heating a had a handy carrot standing by that could be shoved into an open pipe to stop the water flow and to enable me to implement plan B :)

[nothanks]

eee lad, the things tha can do wi' a handy carrot! :-)

[John J]

On some thermostatic rad valves pulling the pin too hard results in it coming out. Followed by a jet of (usually dirty) hot water. Gentle repeated tapping with a toffee hammer is best first line of attack.

[SteveW]

I've been adding them (ball valves) to the piping under the floor, as I move or replace radiators - it'll be a while before I've got a full set though.

I can currently isolate and remove any motorised valve (we have one per room, plus the hot water cyclinder coil one) or radiator inlet valve. I can also isolate the returns from the living room to the manifold. All the radiators are also fitted with integral drains on the outlet valves.

[Robert]

A wet (and dry) vacuum is I find an essential tool for these type of operations. Will quite happily suck any water coming out before it hits the carpet etc.

[John Walliker]

A local plumber told me that the two things that totally transformed the plumbing trade were silicone sealant and wet/dry vacuum cleaners. (He uses silicone sealant in all the places where the cognoscenti here would turn up their noses [and probably for good reason]). He also likes putting isolation valves under floors so that he can work on a particular project in isolation. John

[me9]

And when you come to use them they won't work. However it does help to excercise them every couple of months.

[alan_m]

And then the cheap ones weep from the seal where you turn the valve :)

Possibly better to only install them where they are easily accessible.

In my limited experience the service valves either side of a central heating pump are the worst. In 40 years I've only changed 2 pumps and on both occasions at least one service valve leaked when switching them back on requiring a (partial) drain down and replacement valves.

In my earlier years I made the mistake of fitting some gate valves and when needing them 20 years later found them seized.

[HVS]

On 09 Dec 2022, alan_m wrote

Aside from when one had just been inserted, I've never come across a gate valve that worked as it was supposed to.

Hate them; absolutely hate them.....

[Thomas Prufer]

There is a way:

"IMI Hydronic TRV Insert Removal Tool (9721-00.000)"

which allows the chage of the valve inset, leaving the body in place, using a lock (as in canal) mechanism. Pricey -- may be able to rent or borrow?

And possibly available for other brands of valve.

Thomas Prufer

[charles]

Hertz Valves can also be dealt with in this way. Done it!.

[alan_m]

It works as long as the problem is not with the mating half of the valve. If any residue from the old insert is left (perished rubber washer or broken rubber washer because it previously stuck to mating surface) then the new insert may not work properly.

£150 for a tool to stop you having to drain down is a serious investment.

[charles]

When I bought the tool itb was for a small theatre with about 30 radiators. It would have taken a day to drain down and onther day to refill. I reckoned it ws money well spent on the two occasions I had to use it. By now ( 10 years on) it's probably had a few more outings.

[SteveW]

That's why I'm only installing decent, lever, ball valves, not the rubbish that they sell for isolating a feed to a tap and which needs a screwdriver.