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Another thing is that you say you loose vacuum going up the long mains. How long and how many taps are you talking. For 3/4" I think the max is supposed to be 1000' and I personally think 750' but that's just my opinion. There is also a max number of taps but I forget what that is, someone will chime in on that. If you use 1" mains you can go farther, but I don't have the tubing notebook at hand so I'm not sure how far of how many taps.
A 2" line for 3000' and 2400 taps isn't enough? I don't get it... We can get the same vacuum at the releaser as we do at the top of a sub-conductor that is 15,000 feet from the vacuum pump, going through 7000' of 4", 2000' of 3", 1500' of 2", 1500' of 1.5", 1000' 1.25", and 2000' of 1", reducing down all along the way and picking up 10 other sub conductors, each over 2500' long and starting out 1.5", 30,000 odd taps. This is just the vacuum lines, in general we go down one size for liquid lines. I know because we were checking vacuum last week and the boss wanted to know what the vacuum level was at the top manifold of one of our furthest back conductors, and once we got leaks fixed up it was the same as what the gauge on the releaser at the pump station was reading. That's my experience anyways...
Not sure why overbuilding systems is pushed so much...
The Cornell vacuum book shows that you get 20 CFM from a 30 CFM vacuum pump at 3,000' with a dry line capacity of about 2,030 taps. If the pump is 60 CFM, then you get 25 CFM with a dry line capacity of 2,500.
They recommend 1 cfm per 100 taps to properly transfer the vacuum and overcome small leaks.
Joe