A few 3/16 and homemade vacuum questions intertwined

[Andrew Franklin]

I plan to have 150 taps on 3/16 which will have 30 feet of fall from the last tap. Previously I collected the sap at the point the slope ended and then pumped it from the storage tank to my ro and evaporator about 500' away over level ground. this year I'd like to run the 3/16 all the way to the ro and evaporator. Question #1 - will that hurt the natural vacuum to have that far of a flat run (it will be 30' from the last tap, but a long distance)? Then I thought I would splice the five 3/16 lines into a 5/16 (maybe two feet long, using the bigger diameter to handle the flow) which flows into the storage tank. Question #2 - any negative impact here on my natural vacuum? Then, I thought I'd put a swing valve on the end of that line and a "t" before the valve running into a homemade vacuum system that will shut off the valve and run vacuum when I can supervise. I'm 70 miles away, and don't want the compressor and vacuum pump running 24/7 in case a critter chews things up before I can get back down to my woods. I'll have a camera on the storage tank to gauge collection. Question #3 - I've always used vacuum gauges at the top of my 5 runs to see how they are pulling. If I put another gauge at the end of each of the five lines before they splice into the short 5/16 line will they accurately measure vacuum when I'm pulling naturally without the pump on? I know they will show the vacuum when the pump is on, but what will they read at the end of the run with no pump pulling sap? I should have paid more attention in physics class in high school! I know that's a lot, but it amazes me how much the people on this site know and are willing to share...thanks in advance!

[maple flats]

3/16 on flat or nearly flat ground will not work well unless you have mechanical vacuum on it. Even then, line friction will reduce the flow.
That being said, I may be one of the very few (if not the only one) who do just that. I have runs of 3/16 pulling as much as 4-500' from trees that are nearly at the same elevation, and I have several runs that actually pull from lines a few feet below the main lines. I only have 2 mainlines, both are 1" and I then have 2 sap ladders on each. While my results are good, I'm sure it could do better if I wasn't fighting the wisdom of the experts. This past year I got .49 gal/tap in syrup, the year before I got .52 GPT. Before that I had never used the 3/16 except as designed.
I run 26-27" mechanical vacuum using an antique pump, an old BB4 piston pump.

[maple flats]

I would not suggest you join the 5 at 3/16 into any manifold, 5/16 or other. With about 30' drop in 500', if you are correct, you still have about 6% slope (6'/100'), that should be enough not to loose much if any flow. Run each 3/16 into the tank individually.
2 years ago I bought sap from an Amish farmer who used all 3/16, with enough slope, and he ran the lines into a SS tank, almost 850 gal. His system looked very neat and worked well. I think he had about 700 taps if I recall and when I got there to pump the tank, it was overflowing, at the end of the season, after having been pumped about 32 hrs earlier. (I would have pumped it sooner, but it would have meant pumping on Easter Sunday and he would not allow working on Sunday, which I honored.