PLYMOUTH, N.H.—Love it or rip it out?

A debate is starting to swirl between expert installers on the effectiveness of three quarter inch mainline. Some experts are advising that the narrow mainline does not do well transferring sap on vacuum.

“Regardless of the situation, airtight or not, there are always downsides to using 3/4 in. tubing,” said expert Joel Boutin, an advisor for the Quebec Maple Cooperative. Boutin was a guest speaker at the Vermont Maple School in December who emphasized his dislike of 3/4 inch pipe.

Boutin said that 3/4 inch mainline often acts like 5/16ths lateral lines, overfilling with sap and taking up too much space for air. He said big bubbles will form in the tube and decrease vacuum the further away from the pump.

“3/4 tubing can only carry sap from very few taps with the new yields people can get now,” Boutin told The Maple News. “In fact, it is less than 100 taps if you do more than 6 lbs per tap."

Tubing installer Yvan Doyan of Caanan, Vt. said he also hates narrow mainline.

“What ends up happening is you aren’t able to evacuate the liquid from your system," Doyan said. "If you can’t evacuate your liquid, when it comes time for freezing it ends up heaving up your saddles.”

But other notable sugarmakers say not so fast.

“Half my woods have 3/4 inch pipe and I made 6 pounds per tap last year,” said Glenn Goodrich, of Goodrich Maple Farms in Eden, Vt. who has 160,000 taps. Goodrich is perhaps the most prolific tubing installer in the U.S. Over many decades he has set up hundreds of sugarmakers' woods besides his own massive operation.

Goodrich said he likes using the smaller pipe.  

Goodrich said his rule for 3/4 pipe is no more than 200 taps on a section and he said he tries to keep each section no more 800 feet long.

Goodrich said he installs 3/4 mainline crossways on his slope, with a slight downgrade of 2 to 4 percent.

“I like to save all of my slope for the laterals,” Goodrich said.

Goodrich said he uses a much thicker mainline, 4 inch wet and 3 inch dry as his big "conductor" or trunkline that runs vertical down the hill to the pump house.

Dave Fuller, a 25,000-tap sugarmaker entering his 50th season of making syrup in Jefferson and Lancaster, N.H. agreed that 3/4 pipe works just fine.

"It's b.s. to say otherwise," Fuller said at the New Hampshire Maple Producers annual meeting on Jan.21, where the 3/4 pipe topic came up in discussions.

"Three quarters mainline is almost never completely full if it's set up right," Fuller said. "When you do the math and do a proper layout you can do 3/4, no problem."

"Plus, it's easier to carry around in the woods," Fuller said.