Dumb question

[Bruce J Stuart]

Should I plug the upper end of my 3/4" mainline or would this completely prevent flow?

[maple flats]

Not a dumb question, the only dumb one is the question you wonder about but never ask.
Yes, plug the top to keep critters and debris out. I use a ball valve, then when cleaning the tubing the valve is opened to flush the line.

[Bruce J Stuart]

thanks so much. The ball valve sounds like a good idea. I was just wondering if the plugged mainline would act like a straw does when it is full but you have your finger on the end of it. Just wondering.............

[wiam]

Hopefully it will act like a straw and give you some vacum at the tap

[madmapler]

thanks so much. The ball valve sounds like a good idea. I was just wondering if the plugged mainline would act like a straw does when it is full but you have your finger on the end of it. Just wondering.............

Thats a good thing. It creates vacuum in the system(especially on a slope) which draws more sap from the tree. Keep it as air tight as you can.