How do I change a TRV on a pressurised system?
A couple of weeks ago, I noticed the bathroom floor had 'dried water' underneath the towel rail / radiator. I checked the radiator for leaks, and it was bone dry all around it and the connecting pipes. I left it for a few days, keeping my eye on it, just in case it wasn't a sopping wet towel which had been left, and sure enough there was a signs of a drip. Placing a tub underneath, the following day it collected circa 10ml of water.
Taking off the TRV, I am greeted with the picture below - but it's hard to determine exactly where it was weeping, either around the 'pin' or elsewhere. Either way, the valve needs replacement [although since fannying around with it, it seems to have stopped weeping].
I have seen a couple of you tube videos, they change TRVs, but not on a normal boiler with a two circuit pressurised system. The suggestion is to relieve pressure from the radiator (two pipe system) using the bleed valve, and then close it. Then turn the other radiator valve off (are they called lockshields?) and that will help effectively air-lock the water in the system and radiator (like a finger on the top of a straw), so I can remove the TRV (obviously there will be limited leakage). I would hope to utilise the existing olive/nut etc. Is it that straightforward on a pressurised system? Or would I need to drain the system?