Created with Sketch. Created with Sketch.
Taking Care of the Woods

Taking Care of the Woods

Posted by Dr. Tim Perkins and Dr. Abby van den Berg on Oct 1st 2020

We asked the scientists at the University of Vermont Proctor Maple Research Center to share some tips on how to achieve higher sap yields, and what you should be paying attention to this fall.

Tubing System Design and Installation

To achieve good vacuum and sap transfer in tubing systems, producers should design and size their systems for peak flows. Undersized mainline or systems installed without adequate slope or with sags will not perform well.

Optimal mainline installations have 2-4% slopes with lateral lines running uphill from mainline. Lateral lines should use the “strive for 5, no more than 10,”meaning the number of taps per 5/16" lateral line.

For areas with good slope, 3/16" tubing may be a good choice. The selection of a pump and releaser system capable of achieving the desired vacuum level is also important to ensure you are able to get 1 CFM/100 taps in your woods.


Getting a good taphole in a good location is critical to achieving high yields. Start with a sharp bit designed specifically for maple tapping. Look over the tree closely for a spot where there are no defects, at least 2-4" laterally and 6-12" vertically from the previous year’s taphole, and in a position able to be reached by the dropline. Assume a stable position and drill straight in and out in one smooth motion.

Don’t drill way over your head – this will produce oblong tapholes and vacuum leaks. The spout should be firmly seated in the taphole (go by sound and feel), but not overdriven. A hammer designed for maple tapping is recommended to avoid over-
driving spouts.

Hitting Stained Wood While Tapping

How often do you hit stained (brown) wood while tapping? Stained wood is non-conductive of sap. Thus, every time you tap into non-conductive wood (NCW), you lose yield. More importantly – you’re losing money. If you generally produce about 10 gallons of sap per taphole and are hitting stained wood 5% of the time while tapping, you’re losing a half gallon of sap per tap, averaged across your entire sugarbush. That’s the equivalent of dropping a quarter at the base of each tree just from hitting NCW while tapping!


This relationship is pretty simple – the higher the vacuum, the higher the sap yield. The effect is linear – for each 1" Hg vacuum increase, maple producers can expect a 5-7% increase in sap yield. High vacuum also means that you can alter the recommended number of taps per tree. If you’re pulling 25"+ of vacuum, a second tap doesn’t produce more sap until trees are nearly 20" in diameter.

Taphole & Tubing Leaks:In order to maintain vacuum levels high, leaks have to be detected and fixed. Proper care during tapping as well as design and maintenance of tubing systems is important. Whether producers use manual inspection or electronic monitoring devices, rapid correction of problems is vital.

Spout & Dropline Sanitation

Better spout and dropline sanitation are associated with higher sap yields. However, it isn’t just about getting more sap – it’s a balance between getting the most sap possible at a reasonable cost, or the net economic profit. A decade of work by researchers at UVM Proctor Center, Cornell, West Virginia, and in Canada have shown that Leader Check-Valve Spouts or Adapters are one of the most effective ways of doing this. Check-valve spouts and adapters produce some of the highest net profits of any spout available and alleviate the need to frequently change droplines to keep sap yields high.

Dr. Tim Perkins,
Director, UVM Proctor Maple Research Center

Dr. Abby van den Berg
Assistant Director, UVM Proctor Maple Research Center