Good point about pipe diameter....lots of drains were 1 1/4" which proved woefully too small for anything long term...even 1 1/4" vents would plug with scale easily.
You really should open something up to determine piping diameter of the vac system. The modern vac systems I've seen use 2" or larger piping. Even if your vac system was 1 1/2" it might be a struggle with moderns CV systems. The guys that are familiar with modern CV's in here would know.
Kevin
