Gravity, last tap

[toquin]

Just read an older post about not putting any drops in the last 30-40 feet of your mainline to increase your vacuum on a gravity system. Yes or no. Should I just hang buckets on that last tree next to the collection tank?

[Bucket Head]

I'm not sure about the "30-40 feet" thing. I have 44 taps from start to finish on a 5/16" line thats about 400ft. long. It drops 30ft. in elevation from the top to the collection point. The last tap is about eight feet from the collection barrel. This line has pulled 7 inches of natural vacuum on occasions. When you say mainline, your talking a 5/16" line? If its bigger than that, you probably won't get much, if any, natural vacuum. Natural vacuum on gravity systems relies on small tubing, so the sap fills the line and "pulls" as it flows downhill and exits.

Steve

[toquin]

Yes 5/16. Had one line that had last tap next to tank, sounds like it is staying there. thks

[Spanielslovesappin]

I just read a very interesting research paper on this very issue on the UVM Proctor Site. The jist was that you can achieve sustained high vac on gravity tubing with ample slope and 3/16 tubing. Very interesting! Maybe i don't have to run 3000' of electric line after all? At least not right off the bat.

http://www.uvm.edu/~pmrc/highvacuum.pdf