I have about 75 taps on 3/16 and another 50 on 5/16. They are on two mainlines that converge centrally on a tank. 3/16 on the hill, east side, 5/16 on the flat southwestern side. All on gravity, or whatever vacuum the 3/16 creates. Each year the 3/16 runs great and the 5/16 is very sluggish.

I am using 1" black plastic water line as a mainline. The saddles have gotten worn out and need to be replaced.

I'm going to set up a vacuum with a Shurflo or two. Is there any consensus about which better - multiple lines converging onto a manifold next to the pump - or - using a traditional mainline with saddles which is connected to the pump?

If I go the mainline route, I was going to switch to smaller diameter mainline, probably 1/2" (which should be plenty to handle that number of taps.)
Smaller diameter mainline should promote better vacuum, correct?

The end of the mainline will need to be sealed, correct?

Thanks for any help!