An odd vacuum scenario

[Fireman]

Here is one that struck me kind of odd today. 20 inches of vacuum at the pump, 17 inches in the furthest lateral line (yes, there are some minor leaks), sap lines full of sap, and hardly anything coming out at the pump. Screens are out. This is about 275 taps on 2, 3/4" lines. If I shut down my left line, I get a vacuum increase of about 4 inches, and still hardly anything coming out. The pump is a double guzzler. Of course, I volunteered for some overtime at work tonight, so the issue will need to wait until morning. Plan to pull the manifold off the intake side to see if that clears the lines of sap. The only thing that really makes any sense, the discharge side has to be plugged. Not sure if it would be the duck bill valves of the discharge side, or a clog of gunk from the lines. Which has been seen in the lines with all the warm weather we have had. It has been below freezing for 5 or 6 days, up to 41 today with overcast and drizzle, and yesterday was above freezing, even through the night. I don't think it is ice. When I reopened my left line, I did get a few glop's of sap that looked to have the whole 3/4" line full. But it didn't last long. I think I also want to put a pressure gauge on a tree so I can monitor that too. Just kind of a weird scenario.

[madmapler]

Sounds to me like everything could be okay aside from the small leaks. In fact, that vacuum drop could be the result of gases being pulled from the tree. It's not a high cfm pump. Sap will often seem to sit in the lines. If the sap wasn't running well then you simply won't be pulling much, if any, into the tanks.

[Fireman]

Thanks Sean, that is exactly what is going on. I have some laterals that are slowly moving, some at a stand still, and some that are bone dry. We have had an odd spring. We had a solid week of highs in the 60's, with a day or two at 70. I had wondered if some of the tap holes had healed over. I think this week may be our last week of run, at this point, I don't think it is worth it to re-reem holes, or drill new ones. After I posted this, I scoured through the Cornell vacuum manual. I was leaning towards air coming through the trees and too low of a cfm pump. It is nice to hear someone with the same thoughts. Some day, I will move to a better pump.