i remember seeing a study that said the leak valve or pinhole just made the vac level go down, and kinda believed it till i started watching my 6 way star sap ladder with about 55 taps on it. it appears that with the good tight system i have i end up with more sap than air and the sap tends to fill the mainline at the bottom before it can be drawn up the ladder. it would seem logical this would happen as when there is not enough air coming in then of course the sap cant be drawn up, basicly air locked. so i think i will add a small valve to bleed a tiny bit of air in to help it flow, wondering where it should be, near the ladder or at the far end of the lower mainline? was thinking maybe just a saddle with a 1/8 in pipe valve on a short piece of tubing