3/16 tubing - we are believers

[Goggleeye]

I too have minimal slope and was wondering how this would work. Those of you have been running 3/16, what is your syrup per tap looking like? I run all 5/16 tubing on minimal slope (10-30 taps on 5-20 feet total slope, and the past two years I have produced 1.44 qts and 1.7 qts per tap, with probably over 100 of my 460 taps come from sub 10" trees and many from the 7-8" range. Aren't those pretty good ratios? Do you think 3/16 would put me over 2 qts/tap, weather cooperating? Not that I have the evap capacity to handle more sap!

[StayinLowTech]

I put vacuum gauges on two runs of similar slope, one run of 5/16 and one of 3/16. Yesterday (not a heavy run) the 5/16 line was 3" and the 3/16 was 8" of vac. On a steep slope I often get around 25 to 26.5" vac.

[Forrest hunters]

So this could work with minimal slope and possibly out produce bags. I would just love the simplicity over lugging with the same as i get now.

[DrTimPerkins]

Will this system still work with minimal slope?

Unfortunately not with 'minimal' slope. Without decent slope, the small line results in the development of back-pressure and you'll get less sap than you would with a bag or bucket. Regular 5/16" tubing will probably do better as long as there is a minimal amount of slope. Slope is required with 3/16" tubing, although there is some ongoing research looking at having modest vacuum and various slopes in 3/16" tubing to generate high vacuum.

[BAP]

Dr Tim, has any research been done on 5/16" tubing and the natural vacuum effect like the 3/16"? I was wondering if putting more taps on a 5/16" line would get the same effect as the 3/16 with less taps. Back 30 plus years ago, we used to run lines with anywhere from 30-100+ taps, like a lot of people at that time did, and got a lot of sap of places with steep grades. I wonder if we were getting this natural vacuum effect.

[DrTimPerkins]

Dr Tim, has any research been done on 5/16" tubing and the natural vacuum effect like the 3/16"?

Yes, but a long time ago. As you recall, it takes a good number of taps to fill a 5/16" line, which is why the recommendations for tapping on sloped land with 5/16" is very different between gravity and vacuum lines (gravity lines you want many taps, vacuum lines you want far fewer taps). The 3/16" line will develop a natural vacuum with less taps.

[Forrest hunters]

DrTim,
Can you define minimal slope or what you believe to be the minimum to run this set up. I could probably get 15' from first tap to top of drum I would want to empty into. With that being said what kind of slope do I need for the trees to get there. Maybe put 10-20 taps per line. I could have runs of a couple hundred feet each.

[DrTimPerkins]

Can you define minimal slope or what you believe to be the minimum to run this set up. I could probably get 15' from first tap to top of drum I would want to empty into.

Each ft of head is a little less than 1" Hg. However keep in mind that sap in a line also contains bubbles, which do not contribute to the head. Also, this applies only to the change in elevation from the outlet (the top of the storage drum) to the tree. So if the tap in your last tree is 15' higher than your drum, you might get about 10-12" Hg, but if your last tree is only 1 ft, you'll get almost nothing there. The problem on minimal slope is that (theoretically at least) the capillarity and friction of the tubing starts to play a bigger role in the overall sum of the equation, so if you don't have enough sap weight to push the liquid out of the tubing, it will just add to the friction, and create a back-pressure which can impede sap flow. You definitely don't want to use 3/16" on flat land.

As I've said before, Tim Wilmot (UVM Maple Extension) is the expert on this and has done all of the research, so best to direct these types of questions to him. There is still more to learn.

[Jeff E]

It was mentioned that the number of taps on a line plays a big role, and is different with 5/16 and 3/16.

So for an example, does anyone now the best number of taps for a 5/16 line with 30 ft of head, and also for 3/16 line with 30' ft of head?
And is the best practice to run these directly to a tank, or could you have similar success running to a mainline?

[ryebrye]

It was mentioned that the number of taps on a line plays a big role, and is different with 5/16 and 3/16.

So for an example, does anyone now the best number of taps for a 5/16 line with 30 ft of head, and also for 3/16 line with 30' ft of head?
And is the best practice to run these directly to a tank, or could you have similar success running to a mainline?

The number of taps to get a high vacuum in 5/16 was studied, but in the study they found that 10 was not enough.

For 3/16 - as few as 4 could be enough.

For high vacuum, the minimum number of taps to place on a 3/16" line approximately 150' long is 4 or perhaps even less; the minimum number of taps on a similar 5/16" line is as yet undetermined, but is greater than 10. This assumes a good vertical drop below most of the trees.

(see http://www.uvm.edu/~pmrc/highvacuum.pdf for more details)