On Tue, 17 Sep 2013 11:07:34 -0700 (PDT), John G
wrote:

On Tuesday, 17 September 2013 18:48:32 UTC+1, Davidm wrote:
I fitted new Drayton TRV4 radiator valves to all my rads about 4 years

ago, and already two of them have started leaking where the valve pin

projects from the valve body.

Is this a common problem? Are they fixable or is the only solution to

renew the whole thing? Anyone have a magic solution for doing this

that avoids draining the system (it's an open vented system with a

header tank)?

Most valves have a gland nut on the valve body that can be tightened slightly to stop the leak BUT not too tight to stop the pin moving.
No gland nut on thse valves, the operating pin just projects through a
plastic insert in the top of the valve body (unless the nut is inside
the valve body - which would be pretty useless anyway).