What is the absolute smallest vacuum pump I can run as a test?

[jdircksen]

I am curious how vacuum compares to gravity so I was thinking of putting 1 tap on vacuum so I can see learn how it works compared to a gravity tap in the same tree. This is mostly an experiment that I would watch in my backyard. I'm not finding any tiny vacuum pumps for potable water on google, so I'm guessing I don't know the right terminology for the pump. Any idea what kind of apparatus I could use for the experiment?

[Cider Hill Maple Farm]

JD,

Follow link below, this is probably the cheapest way, but doing a test on one tap isn't really going to prove much. Tie all your taps into one main, and then tie your main into the suction side of the pump. FYI. I would put a small wye strainer before the pump to prevent damage to the pump by ice/wood chips etc.. This is probably a little more than what you want to do though.

https://www.tractorsupply.com/tsc/product/camplux-enjoy-outdoor-life-12-gpm-pressure-diaphragm-water-pump-jk-2202-1485532?cid=Shopping-Google-Organic_Feed-Product-1485532&srsltid=AWLEVJwlO8V8G6XtI7NH7amOnlwScNoGOzv6qO4UxF cgldqiTGefwLdKOeI

[Cjadamec]

You can achieve a decent amount of vacuum with a sureflo pump or the cheap knockoff versions available on Amazon. You just need some valves and a gauge to setup a recirculation line for the pump.

[DRoseum]

UV proctor maple research has shown 4% to 6% yield increase for every inch of mercury vacuum applied at the taphole (inHg). Let's assume 5% avg for talking purposes.

An aquatec 8852 or shurflo 4008 can pull over 20 inHG at the pump if there is sap in the lines without recirculation. Recirc is good for getting the vacuum started and reducing the surging that air in the lines can cause. Took this picture today on my aquatec setup. https://photos.app.goo.gl/pkSBpXGE38nk7Ck19

So 20 inhg will result in 100% increase yield...double the sap!

Now of you have any slope and are using 3/16 tubing you will easily get vacuum levels in the 28 or 29 inhg neighborhood at the taphole. I think it's 0.88in hg per foot of elevation drop, leveling out at 29-30 in hg max. Thats 150% increase in yield.

My experience on my setups (aquatec and shurflo pumps using 3/16 with good elevation drop)it has easily hit that 150% increase in yield from my red maples (which can be very finicky when not on vacuum).

Don't bother with a test. Plenty of data shows that if done right you will get much higher yields.

I know its not a controlled experiment but after I went to vacuum I got over 3 times that of my neighbor who normally got very similar sap flow per tap to me for years.

[Biz]

I have experimented with the cheap 1gpm diaphragm pumps and I was not impressed. They will pump liquid OK but I was not able to pull a steady vacuum with them. It surges a lot, which is a bad thing for a sap line. I really wanted to make it work for vacuum but it didn't. Better off going with a 4008 or similar which are known to work.

Dave

[Super Sapper]

Amount of sap can vary on different taps in the same tree even just on buckets. Putting vac on one tap will also decrease the sap on the tap without vacuum.

[DrTimPerkins]

Amount of sap can vary on different taps in the same tree even just on buckets. Putting vac on one tap will also decrease the sap on the tap without vacuum.

Correct. Comparing two taps in the same tree is not a real good approach to comparing yield.

Think of the tree as a pipe stuck in the ground filled with water. You put in two holes close to each other. On one you let the water run out freely. On the other you pull it out with vacuum. Which will produce more water? Will they interfere with each other? Absolutely...the second hole will produce far less than it would have if there were no second hole (on vacuum or even not on vacuum).

When we put 1 tap in a tree of about 18" diameter and pull a good vacuum (25" Hg), we might get X gallons of sap. If we put 2 taps in the same tree, we get a total of about X gallons of sap, but each tap will produce about 0.5X (on average). Just because you have 2 holes doesn't mean you're going to get double the amount of sap (on vacuum). On gravity the situation is a bit different.

[jdircksen]

Thanks everyone for the ideas and info. I already have a pump with my RO Bucket which is similar to the Aquatec. I was worried it would pull too much vacuum (or too much sap) and harm the tree, so that's why I was looking for a small pump. I guess I could have some kind of adjustable air valve in the system that would allow me to decrease the suction.
My backyard is flat with the massive trees 50' apart. It would take a whole roll of tubing to connect them all, another reason why I was going to just play around with 1 tree. Today we got 1-2" of rain and the chance to avoid walking through the soggy ground is looking better and better.

[DrTimPerkins]

I was worried it would pull too much vacuum (or too much sap) and harm the tree, so that's why I was looking for a small pump.

Vacuum at any level applied to a taphole will not harm a tree. While animal cells will rupture from a vacuum, plant cells are different. They are surrounded by a cell wall, which prevents them from being pulled apart to the point where they break. The internal wound and taphole closure are no different between vacuum and gravity collection. Sap sugar content is also not different. What is different is the sap volume?

Morselli (UVM) demonstrated this years ago up to a vacuum level of 15" Hg. She measured sap chemistry and concluded there was no cellular injury. They couldn't get a vacuum higher than that at the time, so the recommendation to not pull vacuum beyond 15" Hg sort of got stuck in people's minds. We did a study at UVM PMRC in 2007 looking at it and found the same results, but we went up to 25" Hg (as high as we could pull at the time). We also cut up trees and looked at the internal wounding. https://mapleresearch.org/pub/m1007sapcollectionvacuumlevel/

This is the basis for the rule of 5-7% increase in sap yield per inch Hg of vacuum.

These results were confirmed a few years ago by both Cornell and Centre Acer.

The size of the vacuum pump has nothing to do with sap flow or wounding. The differential in pressure drives sap flow, so the higher the differential (inside the tree compared to outside the tree on gravity, or inside the tubing if on vacuum). The size of the pump is more related to ability to how efficiently you can move out large quantities of air (CFM capacity). Some pumps will move a lot of air, but can't generate high vacuum. Others can generate high vacuum (on a small tubing system), but can't move much air. Pumps that move a decent amount of air but can do so to high vacuum levels are what we're really after.