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How to squeeze more sap out of every maple?

The secret, a sugaring expert says, is to use a smaller-diameter sap line

BRATTLEBORO—For attendees at the recent annual meeting of the Windham County Maple Association, food for thought was served alongside coffee, homemade banana bread, fresh cider donuts, and the requisite big block of Vermont cheddar.

University of Vermont Extension Maple Specialist Tim Wilmot and Corse Maple Farm’s Jack Dix presented in-depth comparative analyses of the sap-collection portion of making maple syrup.

While Dix’s portion detailed the results of using different spout treatments on vacuum pumps in six different lots over 10 years, Wilmot’s talk mostly focused on the sap lines themselves.

Through his painstaking research at UVM’s Proctor Maple Research Center, trying out nearly every possible permutation for collecting sap utilizing a variety of techniques and supplies, Wilmot arrived at a few conclusions, which he presented in his lecture.

Wilmot’s overall assertion is that {3/16}-inch PVC tubing is far superior to the standard {5/16}-inch tubing long used by maple syrup producers. This seems counterintuitive, as the tubing he recommends is smaller than the standard.

If the volume is smaller will it yield far less? His studies say no.

He demonstrated support for his findings using graphs, diagrams, charts, photographs, and even a few short films showing sap flowing and bubbling through PVC sap lines.

Wilmot also recommended using a vacuum pump system to yield the most sap per tree. In a chart showing the results of a 2013 survey of Vermont maplers, the relative yield among the three common methods of harvesting sap — individual buckets, gravity systems, and vacuum pump systems — showed gravity-feed systems (the most common method used in Vermont) fared the worst.

“Gravity tubes produce about half as much syrup as vacuum tubes,” Wilmot said.

On average, a producer would do better to insert a bucket into every tree in the lot.

While Wilmot contended some gravity systems are not set up too well, he also acknowledged the cost of adding a vacuum pump system could put that option out of reach of most sugarmakers.

So, how can a sugarmaker optimize yield from each tree — thus reaping the most profit — while keeping their gravity system intact?

Switch to {3/16}-inch lines.

In his example from data collected during the 2012 season — what all agreed was a poor sap year — in two similar lines (similar length, slope, and number of taps in each line), the {5/16} lines brought in 11{1/2} gallons per tap. The {3/16} lines yielded almost double, with 18.2 gallons per tap.

Wilmot told the audience “a {3/16}-inch line develops a better natural vacuum on a sloped gravity-feed line.”

By conducting experiments using different variables — the length of the lines, the vertical distance between taps and the collection basin, the number of taps in each line, the slope of the line — and measuring the suction of each tap using a gauge, he found the {3/16}-inch lines “make a steady vacuum at or near the maximum possible vacuum,” according to the laws of physics.

Wilmot then brought up a slide showing approximately nine photographs of dials against a wooded backdrop.

“To show you I’m not making this up,” Wilmot said, “people are sending me pictures of their vacuum gauges using {3/16}-inch lines,” prompting one audience member to ask, with incredulity, “They’re getting six gallons per day per tap?”

“Yes,” Wilmot said.

Wilmot found the optimal conditions for yield are short lines, few taps, and a good slope: “I got, with the {3/16} line, almost five times the yield of the {5/16} line."

Other best practices Wilmot shared with the audience include using quality materials and maintaining a regular replacement schedule, checking for leaks in the tubing system, and installing vacuum gauges on taps to monitor the suction.

He especially recommends the latter “for starting out, until you get used to where the leaks are likely to happen.”

He provided another practical consideration arguing for changing to the smaller lines: weight.

“If you’re tired of carrying rolls of tubing through the woods every year when you replace your lines,” switch to the {3/16} lines because “these rolls weigh 10 pounds each, versus 14.6 pounds for the {5/16} line."

In his presentation, Jack Dix stressed the importance of yearly replacement of spouts, check valves (a small device inserted into the tap hole that prevents the backflow of sap from the tubing system), and droplines (the tubing connecting the tree tap to the main lateral line that collects the sap and brings it to the basin).

Dix’s exhaustive collection of 10 years of data on the Whitingham farm’s maple syrup production showed that by replacing droplines alone they increased yield so much that “it twice paid for itself.”

But what really made the difference was installing vacuum pumps. Dix said, “In a year with no significant freezes and early hot weather — a bad year for syrup — what saved us was our vacuum [pumps].”

Dix detailed the cost of a variety of check valves, drop lines, and labor, as well as tools to use to replace lines and spouts. He also recommended “as soon as a section is tapped, isolate the line and get a vacuum [pump] up before you tap the rest of your trees. It saves time, and during sugaring season, you don’t have much time.”

Ray Corse, owner of Corse Maple Farm, reminded the group that “things are always changing. There are many variables [to making maple syrup]. It’s really about how much of the sap we get.”

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Originally published in The Commons issue #280 (Wednesday, November 12, 2014). This story appeared on page A1.

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