Plastic twisty part of themostatic rad valve is broken - can I just pop it off?

[AVR2]

I went to turn a rad back on at its thermostatic valve, and whole white plastic assembly just spins as one piece - both the upper section (the part with the number scale, that's supposed to turn) and the lower "collar" section with the little arrow pointer. You can turn it endlessly in either direction and it doesn't tighten or loosen. Trying to hold the bottom section still while turning the top section doesn't work.

Can I just pull/lever the whole plastic section off and turn the rad back on with pliers on the metal spindle thing inside?

 

[Mottie]

Why not hold the bottom bit and turn the top bit?

 

[AVR2]

First thing I tried, oddly enough. Doesn't work.

 

[fixitflav]

I went to turn a rad back on at its thermostatic valve, and whole white plastic assembly just spins as one piece - both the upper section (the part with the number scale, that's supposed to turn) and the lower "collar" section with the little arrow pointer. You can turn it endlessly in either direction and it doesn't tighten or loosen.

Can I just pull/lever the whole plastic section off and turn the rad back on with pliers on the metal spindle thing inside?

There should be a tag on the head (the lower bit which isn't meant to turn), which engages with a slot on the valve body to prevent rotation, but the collar/nut has to be tightened fully for it to engage. If you press the head down and rotate it, you should feel it engage. Then tighten the nut.
The metal spindle thing goes in and out, doesn't rotate (if that's what you were thinking). I've known cases where it's been stuck, and pressing it down with a flat metal object freed it, and it then sprung out. Or you might pull it with pliers, but be careful not to bend it.

 

[Madrab]

The chrome knurled ring underneath the plastic head needs to be tight to the valve, is that loose?

 

[AVR2]

Thanks guys. The knurled ring wasn't loose and pressing down on the head didn't achieve anything, so I unscrewed the ring and took the head off completely.

As you can see from the photos, there's green corrosion emerging from under the spindle and the spindle itself is showing surface corrosion. I started tapping it with the pliers and after a few taps it started moving and springing back up. Is it worth hoovering out the green stuff and spraying some lube down the shaft, or does the green stuff indicate that the valve's already too far gone?

As far as the plastic head is concerned, even after removing it I can't make the upper section turn, it's completely jammed. Does that simply mean it's broken? If so, do the heads have a universal/generic fitment and I can just buy a new one at Homebase and screw it onto the valve, or do I have to get the specific head for the make of valve?

 

[durhamplumber]

You will need to get the specific one.If your rad is hot and it is not leaking,just leave it..,The TRV is not saving you hundreds of pounds in gas bills.The green means it has weaped a bit.Brass expands and contracts muchly with heat,,so have a tendancy to drip eventually.If the rad is cold,as you have discovered,pushing pin in and out frees it.Otherwise,leave it alone.

 

[Madrab]

If the head won't turn then yup, it's jammed. Should be the standard M30 (30mm) if it's a drayton, just give the diameter a measure first.

 

[AVR2]

Difference of opinion there between durhamplumber and Rob - can I use a generic head, or does it need to be a specific Drayton head?

Just looking at the way the heads are advertised, and the reviews people have left on sites like Amazon, it seems like they're universal and intended to be used on any valve body with the appropriate thread size. There are also thread adaptors available for older rads.

Judging by the position of the scale on my one, it looks like it's been forcibly turned past the end stop that you'd hit when turning it off. Which is odd, because I remember turning it off and I definitely didn't force it past the end stop.

 

[Madrab]

If you want a replacement TRV on the radiator then use a drayton with an M30 thread, measure the diameter to check. If it's 30mm then that's the one you need. Any M30 head will fit but get a drayton RT212, that way you know the pin stroke length will be the same, so should work as expected.

 

[AVR2]

Cheers Rob!