On 2006-08-21 00:57:49 +0100, "Graham" said:

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, and most of mine have
weeping steams if not kept fully open.
Are gate valves preferred for this application because they are better
at controlling the flow i.e. nether fully open nor closed?

They tend to be a washer on the end of a plunger which progressively
closes the gap to the seat as it goes down - by rotation or being
pushed by a pin in the case of a TRV. The range of operation is
achieved with quite small movement - about 3-4mm.

If you have weeping valves it is because they are worn out or were crap
in the first place. You can go round tightening them and packing
them, but IME it doesn't last.

I would have a blitz and replace the lot - it's do-able easily in a
morning. Also, I would recommend getting good quality valves. They
cost a little more, but when you consider the time and cost of
replacing inhibitor after draining to fix one valve, it's worth it.

I did this exercise a few years ago and used Pegler Terrier valves for
the lockshields and Drayton TRV4s for the TRVs. For the
lockshields you can get them with a drain connection on the radiator
side of the valve. This is useful and a lot less messy when taking
radiators off for decorating etc.