how much more sap to expect from gravity to vaccum?

[smitty76]

question, being that we have never been on vaccum and are planning on putting our 600 tap bush on vaccum this fall for 20122 season, how much more production is typical from gravity to vaccum? I would assume that the % of increase is the same or respectively the same no matter what the # of taps are. Just corious as to what to expect, 50% more, twice as much sap? Any experience would be helpful.

[Thad Blaisdell]

With the right vacuum you can expect to make twice as much syrup. With that you can expect more than twice the sap. With vacuum you will find a lower sugar content but much more fluid. With the right vacuum on 600 taps you could make 300 gallons of syrup.

[maple flats]

And maybe even significantly more. Don't bank on it but one test trial got 1.09 gal syrup/tap using check valves. If you never shut off the vacuum unless everything is frozen solid 100%, the check valves are not needed.

[wiam]

And maybe even significantly more. Don't bank on it but one test trial got 1.09 gal syrup/tap using check valves. If you never shut off the vacuum unless everything is frozen solid 100%, the check valves are not needed.

I disagree with that last statement unless you have an electric releaser. You will see vac fluctuations at the tree with a mechanical releaser. If you feed with a big enough line you will not see it at the releaser, but it will be there.

[DrTimPerkins]

I disagree with that last statement unless you have an electric releaser. You will see vac fluctuations at the tree with a mechanical releaser.

I also would have to disagree with that last statement. Our vacuum pumps were not turned off the entire season, yet we saw a 35.9-57.5% increase with CVs in our testing in 2011. We have mechanical releasers.

[Cardigan99]

Smitty, here's a link to a paper on vacuum rates vs gravity authored by Dr Tim et al.

http://www.uvm.edu/~pmrc/vacsap.pdf

See the graph on p30 (4th page). I've gotten roughly 6 gallons per tap on gravity (zero vacuum) for the last five years. This year I'm going to vacuum with a delaval 73 that will probably run something like 15 - 18 hg so I should get around 15 -17 gallons per tap all else being equal. That's a pretty substantial increase in sap.

Todd

[smitty76]

thank all of you for your info. Sounds like it clearly makes a differeince, in fact it excits me. we are building a releaser and still need to get a pump, but have plenty of time for that. Now i am going to check out that link, thanks Todd.

[DrTimPerkins]

thank all of you for your info. Sounds like it clearly makes a differeince, in fact it excits me. we are building a releaser and still need to get a pump, but have plenty of time for that. Now i am going to check out that link, thanks Todd.

Hi Todd,

Just be aware that putting a pump and releaser on your mainline aren't enough to achieve high sap yields. Of equal importance is keeping your system as leak-free as possible to maintain good vacuum in the woods. This means checking the lines at least every few days, detecting the leaks, and fixing them promptly.

[smitty76]

Thanks Dr Tim and we are aware of the importance of a leak free system. fortunately, the bush is just down the road from my house and can easily stop by every day.

[spud]

Dr. Tim

I am in the process of setting up my woods. Seeing that everything is new would i still benefit from using CVs on my first year. I plan to run my vacuum 24/7 during sugaring season. Thanks.

Spud

[DrTimPerkins]

Dr. Tim

I am in the process of setting up my woods. Seeing that everything is new would i still benefit from using CVs on my first year. I plan to run my vacuum 24/7 during sugaring season. Thanks.

Spud

The benefit of CVs on a new system is likely to be very slight. The improvement in sap yield generally increases with system age, however even a system that is only a couple of years old should experience a significant improvement.

[Sunday Rock Maple]

Any value in using them on a new system to establish a baseline, or does yearly variation negate that?

[DrTimPerkins]

Any value in using them on a new system to establish a baseline, or does yearly variation negate that?

There are many factors affecting sap yield. The two largest are vacuum level and taphole sanitation. If you have good vacuum and new tubing, you're pretty darn close to optimal conditions (using currently engineered tubing systems ;)). If you tap real early or if the season turns out to be fairly extended, using CV adapters may increase your production slightly (5-10%, most people can't measure that closely), particularly if you have a mechanical releaser and if you shut your pumps down during the season regularly. If you have an electric releaser and you never shut your pump off, the advantage will be closer to 0-5% on a brand new system. The advantage gained in using CV adapters is in subsequent years as tubing systems get older and more contaminated with microbes. You won't exceed the sap yield of a new system (within the range of annual variability), but you'll manage to avoid the steep drop off to lower sap production levels that you'd experience if you didn't use CV adapters.