So, I'm taking a radiator off, awkward position in downstairs loo, probably came with the house 30 years ago. Closed valves and managed to unscrew one end (v. difficult, v. stuck, but with no damage to pipes). Drained the water out, no problems no leaks. Thermostatic control end, my spanner knocked against the plastic cover and it started to crack. I quickly removed the spanner and went to push it back into place and it came off in my hand.
The whole thing.
It must have turned slightly as it came off as suddenly the water is back on and gushing out the other end!!! Cue me shouting lots and struggling to see if I can manually stop it with the spanner but it's sheared off right on the level. Pulled up my big girl pants and got on with reattaching it at the other end, so it's okay for now...
But to replace the thermostatic control bit, do I need to drain the central heating or just turn off the water at the mains?
I think you can see the retaining ring in the pic.
Other brands will not be identical, but are somewhat similar.
They are normally supplied with a spare screw-down cap that can be used to turn the valve on and off if the thermostatic head is removed. They're called "decorators' caps" because plumbers think that decorators will break the heads, or spill paint on them, or perhaps steal them, so they often take the thermostatic heads off until other trades have finished. Householders usually lose these caps, or throw them away, at the first opportunity.
Having googled vented systems, I discovered that there are no outlets on any of the radiators to drain the system down! So some more googling I worked out that my best option is taking another radiator off and using that to empty everything! But if I can just replace the head than that's brilliant!
A quick search on YouTube for replacing thermostatic controllers got me Derek (who taught me how to take the radiator off in the first place), which led me to the realisation that, temporarily, I could just take one off another radiator in order to turn the water off and...