3/16 gravity vacuum question

[DJ87]

Hello I am new to this site but finding lots of useful information. Just wondering if anybody with 3/16 tubing on gravity vacuum has checked the vacuum at their lowest tap? I have two, one thousand foot lines. One has twenty five taps and the other thirty five. The twenty five tap line has 27" of vacuum at the top but no vacuum at the lowest tap. Thirty five tap line has 18" of vacuum at the top but only 8" at lowest tap. I have sixty to seventy foot of drop from my lowest tap tap collection tank.Just interested if anybody has checked vacuum at lowest tap.

[wurmdert]

How are you measuring vac a liwer taps

[BSD]

I'm fairly green at 3/16 but i'm fairly confident in my understanding of it from deploying a few thousand feet of it myself this spring. you can really only check for vacuum at the top of the line accurately, and vacuum is only going to theoretically as high as the elevation from your last tap to the tank. The vacuum may be reading lower despite your large elevation drop because there may not be sufficient sap in the line to generate full vacuum, that is why they say you need 12 taps minimum on a line.

[psparr]

It seems like you have some leaks in the line somewhere. You should have near perfect vac with the drop after the last tap.

[Ivyacres]

I believe 3/16 vac is highest at the top to lowest at the last tap. UVM Proctor has found that to be true, but also how much drop is after the last tap or where you are taking the reading from? You could have 25"of vac if you had another 40 ft of drop after that last tap. Check the research Tim Wilmot has done. Good stuff.

[DJ87]

I have a vacuum gauge at the highest and lowest tree. From the research I have read I understand it's possible to have back pressure on lower taps if you have to many taps on one line. So that would mean that at a certain point you start loosing vacuum?

[325abn]

How long of a run do have over that 60 - 70 feet of drop after the last tap?

[DJ87]

Around three hundred twenty five feet.

[BSD]

I have a vacuum gauge at the highest and lowest tree. From the research I have read I understand it's possible to have back pressure on lower taps if you have to many taps on one line. So that would mean that at a certain point you start loosing vacuum?i think your gauge may be compromised, check to see if there is sap up into the lower gauge. you really just need a gauge at the top. vacuum is vacuum

[DJ87]

I am positive my vacuum gauge is working properly. Has anyone ever attempted to check vacuum on 3/16 gravity vacuum at lowest tap?

[maple flats]

I'm adding a few today or tomorrow, but I use a hybrid system, I have a vacuum pump and the 3/16 where the slope is good so mine may not tell you much. At the top tree I expect max vacuum, at the lowest tree I'm hoping to gain a little but not much over the vacuum pump generated vac.

[DJ87]

Wouldn't mind knowing the results even though your system is different than mine. I am just trying to figure out the right number of taps per line to achieve as much vacuum on the whole line instead of just at the top.

[peteinvermont]

This might sound obvious, but do you have sap running in your tank? Meaning, all 1000ft of that lateral, without any T's, is full of sap.


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[DJ87]

My lines are full,other than the bubbles that are normal with sap flow. But on heavy runs the bubbles in the lower taps are near a standstill. That's why I installed vacuum gauge's at the lowest trees so I can see if my line is overloaded.

[Clem3]

I have no experience with 3/16 lines until this year. Just put 50 taps on 3/16, 5 different lines. Has been very warm and now below freezing. Do you just wait for the lines to thaw out? Will they just start running by themselves as the thaw? Anything I can do?

[BSD]

My lines are full,other than the bubbles that are normal with sap flow. But on heavy runs the bubbles in the lower taps are near a standstill. That's why I installed vacuum gauge's at the lowest trees so I can see if my line is overloaded.
i believe the rule of thumb is less than 3 dozen on 3/16. I would try to section out some of them and see if that helps your problem with that line. Most of mine are 25 average and seem to work well. I had 37 on one line but i ended up splitting it off and adding a new line to pick up another 16 trees. my best lines pull 23" and my others average 15" i have some leaks I need to try to identify with a stethoscope on those lines.

[BSD]

I have no experience with 3/16 lines until this year. Just put 50 taps on 3/16, 5 different lines. Has been very warm and now below freezing. Do you just wait for the lines to thaw out? Will they just start running by themselves as the thaw? Anything I can do?mother nature will do it's thing and get them moving once it warms up all by itself.

[DJ87]

I did an experiment and ran a third line and T'd in to both lines so sap could get away father up the hill. This boosted vacuum by 5 to 7 inches at my lowest trees.

[BSD]

I did an experiment and ran a third line and T'd in to both lines so sap could get away father up the hill. This boosted vacuum by 5 to 7 inches at my lowest trees.can you please explain this a little more thoroughly?

[DJ87]

Sorry I didn't reply sooner, its been a little hectic the last few days . Basically I ran a third line and T'd into one line about twelve taps done from the top. And on the second line I put a T in between the tenth and eleventh tap and ran a lateral downand T'd into my third line. This allows sap to flow down the third line so line 1 and 2 aren't overloaded.