Quote Originally Posted by BlueberryHill View Post
"air-sap-air cycling/stalling created by a bad tube approach before inlet." Could I trouble you to describe what a bad approach is? This sound like and issue I might have had but I am really not sure of the difference between a good approach and a bad approach. Thanks!
Let's take a sec to understand the problem (I think Guzzlers would suffer from this issue, too):
Assume your pump can create 25" of vac when wet and only 12" when dry. Start up your pump and have it churn through tons of sap and build up 25". Then there is a section of 100% air arriving at the pump. The pump cannot pull (with 12" power) against the 25" sucking force against it that has built up in the tubing. It will not back-flow, but nor will it pull the air through or even any sap that might arrive to the doorstep later. Eventually the trees will flow more air/sap and the tube pressure will drop to 12" and the pump starts to move again. If it has an accumulation of sap waiting there, then it will raise the vac to above 12" again (maybe only 15" this time because there is less sap) and the cycle continues if another 100% air pocket arrives.

The solution:
Keep a trickle leading into the inlet. When a mainline is too steep or has an uphill section then sap columns form and don't break up or "release forward" as effectively as when the line is gently sloped downward. Inspect your mainline intake on the last 6-foot section and try to make sure air is always over the top of the sap flow there.

You can see my setup on the hobby vac link in my signature to see what I aim for with my inlet flow. Hope this helps.