When we purchased VIP eons ago, I was told to always be diligent about
changing the first alcohol station after the last NBF station to keep the
lines of processor from plugging up with ppts, and to use FRESH 70%
and not rotate an 80% or 95% station down (this makes the problem worse).
How often you change the 70% is dependent on how many tissues/cassettes you
run through in a day/week.  Heavy runs usually meant more changes of 
70%, and 95% was never rotated down, first one discarded, second rotated
down and a fresh 95% in the second spot, result is never had plugged lines.

If you use higher percentage alcohol (95%) in this first station, the problem
is much worse.  I believe this is also one reason for doing a hot water
rinse before the next processing cycle, to make sure there is no crud blocking
the lines, a vendor recommendation that came at a later date. 

Observed one tech, using older carousel processor, set up
processor with fresh reagents, starting with NBF,  70, 95, 100 etc.
and after a couple of days with full runs going, rotate the 70% out, rotate the
first 95% down, and add a new  100%.  NOT a good idea!  The carryover of
water will never adjust that 95% to 70%, and  her solutions looked very
cloudy, with ppts everywhere.  My question was what was this doing to the
tissues, poor things!  I think the idea was to save money without
consideration on what happened to those tissues.  Certainly was not a 
true gradient of alcohols for good dehydration, in my estimation and 
the savings was sooooo minimal compared to having good tissue sections.

Gayle Callis