Vent the main line or cap it off?

[cjf12]

I am running about 400ish taps all on 3/16 into a 3/4 mainline. The mainline is not vacuumed at all other than decent slope. Was wondering if the top of the hill end of the mainline should just be left open to allow it to vent for better flow.

[Russell Lampron]

You'll want to cap it to keep bugs and other stuff out. The pipe doesn't need to be vented to flow good.

[Potters3]

Cap it, as the sap flows it will build up vacuum in the pipe. There has been many threads on here of people get 25" of vac on the tops of the mainline just using natural flow.

[cjf12]

Cap it, as the sap flows it will build up vacuum in the pipe. There has been many threads on here of people get 25" of vac on the tops of the mainline just using natural flow.
I was wondering if that was possible. Any idea on how many taps it took to make 3/4 start to create vacuum?

[mol1jb]

I wouldn't worry about natural vac on a 3/4 inch mainline. If you want to add vac do a small diaphragm pump like a shurflo on the end of your mainline. That is what I have.

[TapTapTap]

I think the 3/4" mainline wouldn't form a vacuum since the key to a vacuum is a fully saturated small diameter line that doesn't allow air to flow by and release the upstream vacuum.

I do agree that you should put a cap on the top end to eliminate pests from entering the tube.

[maple flats]

Cap the end. You will not get natural vacuum on 3/4" line, the sap passes the air (gases). You can only get natural vacuum if the tubing is filled completely. If you want natural vacuum you need to use 3/16 lines and have good total drop in elevation. With 3/16 the sap will not pass the gasses, thus natural vacuum.