Natural vacuum versus clear lines

[Kettle Ridge]

I am fairly new at this and do not use vacuum. I am having a debate with my college graduate son. He thinks that making the laterals airtight is like putting your finger over a straw, trapping the sap at night and letting it freeze, whereas opening the top of the line would allow all sap to drain out to the mainline at night. I see his point, and I am concerned that frozen laterals might reduce output and increase bacteria if the trees want to put out the next day, but I also read that natural vacuum in airtight laterals is a good thing to shoot for. Are these concerns valid? Thanks in advance.

Joe

[cadocter]

Keep your lines closed. I know how the father/son thing goes, but I see it from the other side. Leaving the lines open will help introduce even more bacteria. Also, keeping them closed will allow better production because of the benefits of natural vacuum.

[DrTimPerkins]

Your choice. Numerous studies have shown that if you vent your lines you'll get 33-50% less sap, or you can keep them airtight and get more sap.

[adk1]

Closed is the way to go. I have not put a pressure gage at the end of my mainline but with my slope and when my laterals are full of sap I bet I have good natural vac. One time I removed my stuppy at the very end tree of one my laterals and I could hear the vac suck as soon as I did. I was actually startled by it!