Natural vacuum pressure

[CTsugarMan]

Anyone have an idea on natural vacuum pressure? on 3/16 line? What is good? Is there a relationship between Lenght or amount of taps. I never was concerned with the natural vacuum pressure, but I was now wondering what it should be?

Is it on the entire line or is it different at different locations?

Any insight would be appreciated

[VTnewguy]

It depends on the amount of slope and length from the last tap. Steeper the drop, the better the vac.

[motowbrowne]

Anyone have an idea on natural vacuum pressure? on 3/16 line? What is good? Is there a relationship between Lenght or amount of taps. I never was concerned with the natural vacuum pressure, but I was now wondering what it should be?

Is it on the entire line or is it different at different locations?

Any insight would be appreciated

Vacuum (the opposite of pressure) is measured in inches of mercury (at least around here, though there are other units). I think on earth you can achieve a maximum vacuum of somewhere around 29-30 inches of mercury. Probably depends on your elevation or some other factors.

With regards to sap tubing and natural vacuum from 3/16, any vacuum is good. More vacuum is better. You need enough taps to fill the line and create a column of sap (guideline is at least 7 taps on a line I think) and if you have too many taps (over 25) it may overrun the line and reduce your vacuum. The vacuum is created by the weight of the column of sap. There may be some friction loss, but not much, so the slope isn't as important as total elevation drop. The amount of vacuum at any given place on the line is determined by how much drop is below it. Ideally you'd have at least 30' of elevation drop after the lowest tap on the line. That'd give you the most vacuum possible, but really, any vacuum is better than none. Also, watch out for leaks. One little squirrel chew can let in air and destroy your vacuum.

[CTsugarMan]

Is the drop figured from first highland tap to collection point, or from last tap to collection point? I have about 30+ feet from last tap to collection point, but the drop is about 10 feet between those two points.

Thanks

[motowbrowne]

Is the drop figured from first highland tap to collection point, or from last tap to collection point? I have about 30+ feet from last tap to collection point, but the drop is about 10 feet between those two points.

Thanks

Both. If you have 30' of DROP, not slope after your lowest tap, all the taps should have close to maximum vacuum while the sap is running. If you have less than that at any of your taps then they will be subject to correspondingly less vacuum. Does that make sense?

[hodorskib]

I have lines with 75-100 foot drop from top to bottom and also about 40 they all produce vacuum which is better than none at all. In the past two years I have increased production by 25-30% so no complaints. All of my lines have at least 40 feet from the last tap to the container. I had only 20 last year but when I removed the last two taps on each line it greatly improved.

[maple flats]

I run a few gauges on my lines and at the top all have over 30 of elevation drop. At the top the gauges read 28-29" on high barometric pressure days, a little less on low pressure days. Then on some of those same lines I also put gauges at about 15' above the mainline (in elevation, not distance from the mainline. When the pump I also use is not running those usually have about 12- 13" of vacuum, but when I turn on the pump (which is regulated at 19" because the tank is a vacuum tank which could implode if run higher vacuum) I get 28-29" of vacuum there too.
As you get down the hill more, where the elevation from the bottom outlet of the to any tap is less than 30 or more feet, the vacuum will be less. Typically a figure of .88" of vacuum for each foot of drop in elevation.

[CTsugarMan]

I have lines with 75-100 foot drop from top to bottom and also about 40 they all produce vacuum which is better than none at all. In the past two years I have increased production by 25-30% so no complaints. All of my lines have at least 40 feet from the last tap to the container. I had only 20 last year but when I removed the last two taps on each line it greatly improved.

How many taps on the line do you have?

[hodorskib]

I have 4 separate lines and have between 19-25 on each. After two years no complaints other than the increase is sap.

[BSD]

I have 4 separate lines and have between 19-25 on each. After two years no complaints other than the increase is sap.

the newest set i put out this season i put 33 on 2 lines. and i've got a third line which i want to put only 25 on and see if there is a difference. i suspect it comes down to total linear ft and tree spacing. my theory is that if there are still lots of air-bubbles in the lines then there is room for more taps. my 33 tap runs are nearly solid streams when they hit the tank.

My older woods i have 23-27 tap averages on those lines. and they have a good mix of bubbles/solid.