I showed these two videos at the North American Maple Syrup Council Annual meeting last week and thought you folks might like to see them.

The first shows sap backflow resulting from a sudden leak in a lateral line for a NON check-valve spout. The liquid is dyed blue so it can be seen better.

http://www.youtube.com/watch?v=D1wQPrgzroA

When we did the same thing with a Check-valve spout, the ball snapped back immediately and there was no sap movement back into the taphole.

The second video shows what happens in a mechanical releaser when it dumps and introduces air. This is a single-pipe system. Same thing happens in a double-pipe system, but you can't see it because the air runs up the dry line and doesn't affect the wet line for several minutes, by which point it is much less apparent.

http://www.youtube.com/watch?v=__9xGeunEK8

Tim Perkins
UVM PMRC