"DanG" wrote in message
news:JqLce.334$yV4.173@okepread03...

Our plumbers have gone to working the valves in the closed
position (this assumes new piping, no water or steam present)
with a wet rag on the valve. The imperfection that is created
is in the open position and the closed position is smooth and
functional.

Hi Dan,

Are you sure about the valve orientation that's causing the leaking? What
you've described seems counter-intuitive to me.

When a ball valve is open, then the smooth, solid, uninterrupted sides of
the chromed ball are against the Teflon seal. When a ball valve is closed,
then the through-hole of the ball is pressing against the Teflon. If the
Teflon were to get hot enough to deform, then it would seem that it would be
better to have the smooth, uninterrupted sides of the ball pressing against
the Teflon, rather than the part of the ball with the through-hole in it
(which would allow for an impression of the hole in the deformed Teflon
seal).

Have you tried taking two ball valves apart (one heated with the valve open
and one heated with the valve closed) to examine the seals and see what is
causing the leakage that you've encountered?

Regards,
Michael