I had a major flood this morning. I'm in the precess of decorating the (upstairs) spare bedroom and removed the radiator a couple of days ago to get behind it - having turned off the lockshield valve with a spanner (yes - I did note its position in order to put it back as it was and not upset the balancing) and having replaced the TRV head with the plastic decorating cap which came with it.
All was fine for a couple of days but when I got up and went downstairs this morning, water was pouring through the lounge ceiling and completely swamping the carpet. On investigation, I discovered that sometime early this morning the decorating cap had shattered - allowing water to pour out of the valve. I'm still kicking myself because I could so easily have fitted a short bit of blanked-off pipe to the valve - but didn't deem it to be necessary.
I won't make *that* mistake again! BE WARNED!