I run a few gauges on my lines and at the top all have over 30 of elevation drop. At the top the gauges read 28-29" on high barometric pressure days, a little less on low pressure days. Then on some of those same lines I also put gauges at about 15' above the mainline (in elevation, not distance from the mainline. When the pump I also use is not running those usually have about 12- 13" of vacuum, but when I turn on the pump (which is regulated at 19" because the tank is a vacuum tank which could implode if run higher vacuum) I get 28-29" of vacuum there too.
As you get down the hill more, where the elevation from the bottom outlet of the to any tap is less than 30 or more feet, the vacuum will be less. Typically a figure of .88" of vacuum for each foot of drop in elevation.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.