I've been changing the thermostatic radiator valves on my radiators.
My understanding (obviously wrong) is that if the TRV is turned off and the lock shield is off, that at that stage no water is getting put through the radiator, so by taking off the TRV you'll have to catch the entire contents of the radiator and then change the TRV.
In my house there is a pipe from the floor into the TRV, and then the TRV goes into the radiator. Is this the reason why it needs draining first - because the pipe from the floor will still pump water?
I had a leak earlier at the tail and was able to isolate at both ends, bleed the radiator (then tighten back up) and unscrew the tail. It obviously leaked while I applied PTFE tape but in this instance I didn't need to drain the radiator. It did, however, continue to leak more than I was expecting (one radiators worth).
Could someone clear this up for me please?