In article ,
"Graham" writes:
Thanks for the replies, They mostly confirmed my gut thoughts about the
matter.

One follow-up if I may?

What about radiator lockshield (and non-TRV) valves?
they are usually, if not always gate valves,

Actually, they aren't gate valves.

and most of mine have weeping
steams if not kept fully open.

That's a different problem -- the stuffing box wants
repacking (might just get away with tightening down
the nut, if you can find a compromise where the valve
can still be turned, but it stops leaking). Usually,
you have to dismantle to clean up the shaft once it's
been leaking, as the shaft will have become encrusted
which also prevents sealing.

Given how cheap these valves are, it's probably not
worth bothering to repair one nowadays.

Are gate valves preferred for this application because they are better at
controlling the flow i.e. nether fully open nor closed?

Gate values are good for controlling flow, where you
might want them fully open with minimum pressure drop.
They aren't good at sealing off, particularly dirty
water. (Generally you do want radiator valves to be
able to seal off.)

--
Andrew Gabriel