My old VM head had a 3/4" offtake on a downward angle to the
condenser. When i would open the gate valve i would get a rush
of liquid and then it would settle down to a few drops per sec.
.this still seemed to top out at about 93-4% i then wondered if
this was dew to the very small amount of condensing goign on
befor the condenser...
So after re-brazing on the offtake to a VERY slight upward angle
(enough to make sure any liquid would run back to the columb) i
retested and found it was producing 95.5-96%
this works well but has one draw back: when the valve is first
opend it takes a while for the vapor to be drawn down into the
tube but this can be speed up by opening the valve fully. i
suspect this has someing to do with a chimny effect.