I observed strong sap flow into my drops at the upper portion of my 3/16" line and basically no flow into drops at the bottom portion. I realize vacuum is much lower on bottom portion but I expected to see some flow. I don't know anything about this Bernoulli guy but wonder if sap flow from the line above is restricting flow on lower trees. Has anyone experimented with connecting 3/16" tubing to 5/16" tubing part way down the slope to "open things up" where there is less vacuum but a lot of sap coming from the top?