Why don't TRVs close completely watertight???

Question

In my previous house I thought it was because my TRVs were cheap and nasty that they didn't close completely. This made it impossible to remove a radiator for an extended period of time, as the TRV was dripping at the rate of a maybe drop per second at ~1 psi pressure even when closed as tightly as possible.

In my current house I have brand new, well-known UK name, good quality, expensive, reversible flow TRVs. I decided to move the misplaced radiator in the dining area, and thought I could disconnect it and hang it in its new place before starting on rerouting the underfloor pipework.

Fat chance. Not even violence will stop the TRV from dripping when the radiator is disconnected. Are there some stupid technical reasons for why TRVs should not be able to close completely???

Colin Stamp · Accepted Answer

The Honeywell ones I fitted a couple of years back came with "decorators caps" that fit in place of the thermostat head and screw the valve pin right down. I've never tried them out though...

Cheers,

Colin,

Andrew Gabriel · Answer

Most thermostatic heads don't have an 'off' position.If you want to switch them off, you remove the head andfit the decorator's cap which was supplied with the valve.

John Rumm · Answer

And if you have lost that, remove the head, insert 5p coin, replace the head and screw on tight.

Rednadnerb · Answer

What a great tip, wish I'd known that before now!

cs · Answer

A bit of an expensive solution ;-) but 5p and a piece of sticky tape seems to have done the trick - thanks!!!

Owain · Answer

Remember and get those 5ps back before you move house :-)Owain

Calvin · Answer

Something's been bothering me about cs's reply. Please tell me you've done what was suggested and screwed the head back on with the 5p trapped between it and the pin. That mention of sticky tape gives me an image of a 5p held onto the pin with tape. Not good. But if that's what you've done you'll have found that out by now...

Stuart · Answer

Probbaly just used the tape to hold the coin in place while the headwas screwed back on .Stuart

Cordless Crazy · Answer

My Honeywell ones do when you turn them to zero. Took off all my radand replaced them just by doing that--Cordless Crazy

cs · Answer

Nah, just to keep the 5p in place, took me a few attempts to figure outhow to defeat gravity, if I'd been chewing a gum at the time I mighthave tried that instead...

Why don't TRVs close completely watertight???

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