3/16 drop line length and achieving vacuum on plateaued sugarbush

[Suckmytap]

Hi all - im installing our new 3/16 gravity vacuum system and have run into a three questions.

1) does it matter / is it more efficient to use 5/16 or 3/16 drops?
2) does the drop length matter?
3) for a plateaued sugarbush, does the last tap on the lateral need to be at least at the top of the slope
or can the last tap be on the flat section as long as the end has the required vertical drop from the last tap?

The third question is my big concern. Our sugarbush is plateaued, with the trees on a mostly flat area and a hill with ~30 ft of drop (~10% grade) that abuts the plateau. there are very few trees on the hill. I have it designed so there is a slight slope between trees on the plateu, then carried about 20ft at low grade to the edge of the plateau, and then the line does a straight shot down the hill from there. So technically, there is the 30' of vertical drop between last tap and end. However I'm worried about back pressure causing the sap to get "stuck" on the plateu and not being able to reach the steeper grade. My solution is to have at least one tap at or on the pitch to act as a primer. Thoughts???

[mountainvan]

5/16 drops have more options for spiles, I'm using 3/16-3/16-5/16 ts now.
Drops should be at least 30" to reach more areas of the tree .
Last tap can be anywhere, but for best vacuum on that tree you should have the drop below it.
I have many runs of 3/16 on a flat and then straight down a cliff or very steep slope and the vacuum is 26". I have even started adding 3/16 tubing to the end of my older 5/16 lines, then running the 3/16 down the mountain to a spot lower on the mainline to increase the vacuum on those trees. Best run this year on that bush was 2,500 gals of sap from 800 trees in 12 hrs.

[psparr]

5/16 or 3/16 no difference. Drop length won't affect vacuum. Make them long enough to hit the tapping band of the tree for a few years.
As long as you have some slope the whole way your good.

[StayinLowTech]

About the drops, it is better to have 3/16 drops because you do not get vacuum until the tubing is full and it is harder to fill 5/16 drop by drop, so you get vac quicker with 3/16. Most manufacturers now make spouts for 3/16 tubing so they are easy to find.

[maple flats]

Either on the drops but it matters little where the last tap is, on the plateau or part of the way down as long as there is still a decent fall after the last tap. Even on a plateau with the last tap on the flat, it will take little time for the 3/16 to fill and start down the slope at which time it will start to pull as more sap makes it to the slope. Before long you will have high vacuum as long as you have a tight system and the drop you say is there. In fact, last season I had a similar situation and a 6" limb fell on the 3/16 tubing, pushing it to the ground just barely as the slope began. As I approached it to remove that limb it was very interesting to watch the sap/air/sap/air move rapidly from the top to under the limb and then back up a climb of about vertical 6' to the next tap and the continuing down hill to the mainline about 25' elevation below it. It seemed to make no difference that the limb was holding a section down to the ground and then had to climb back up. From evidence in the snow, the limb had been down since during the night when we had a freeze, and it had filled the line to push itself under the limb and back up to the next tap and continue down to create the vacuum to speed up the flow.

[Super Sapper]

As far as filling the line, once it fills it will stay full as long as there are no leaks. I would go with the 5/16 for drops as this will give you the option to use the check valve spouts which can help increase your yield.

[markcasper]

Since you brought up checkvalves, a question was asked recently at a seminar where the presenter was not in favor of checkvalves. He said don't shut the vacuum off....ever...no need for check valves. So that brings up the next question, how can you ever do maintenance on the pump, releaser, without shutting down the vacuum?? Being that the presenter indicated not to shut the vacuum off would suggest to me there is some benefit to using checkvalves. Not trying to hijack the thread.

[WESTVIRGINIAMAPLER]

We had a presenter last weekend from Proctor that said the same thing. There were producers that had used check valves there on vac and had a bunch of them stick closed from the sugar gluing them shut. Also had a producer that put up a couple hundred new taps on 3/16 last year with check valves and after second or third run they said about all of them stuck shut and sap quit running.

[Suckmytap]

Thanks all. Really appreciate the help.

Also wondering what is the magical number for taps per lateral for natural vac 3/16? I've seen the research that says at minimum 4-6 and at most 25? Have you all had bad results with overloading the 3/16 line and hurting vacuum? Basically I have several laterals with 9 taps and then others further up the hill with 20-25, and I will save myself ~200 ft of length per lateral to my tank if I can combine the back to the front. Should also note that my setup is all laterals to the tank (no mainline) because most of my vertical drop is below the taps, so I need to run extra length dowhnill to the tank to get the vac. Both scenarios would have the same drop and distance to the tank, just depends if I run an extra 200ft for 4 laterals or 2. If I combine then I would have about 35 taps on one lateral. Do you think that will be ok?

[psparr]

35 is a good number.