This was mentioned in my TRV4 thread, but wasn't the main subject, so I'm starting a new thread.
I've already discounted using valves with the drain-off in the tail because they would likely foul the out-turned seam on some of my rads as they were screwed in.
Looking at the BES online catalogue, there appear to be at least two types with outboard drain-offs - the 15mm ones being #7783 and #7508 respectively. I can see how they differ in appearance, but would someone care to explain how they differ in *function*? The second one apparently has a drain-off to BS 2767, Type 10. Anyone know what that means in real money?
BES also do a "Radiator Drain Off Valve" (part# 7509) which doesn't actually appear to be a radiator valve! Anyone know what that's for?