Can you put 5/16" tubing and 3/16" tubing into same mainline?

[letmgo]

I have a 250 foot 3/4" mainline with 180 taps flowing into it. About half the lines are 3/16" tubing that have been running real well. Some of the flatter lines are 5/16" tubing. Where both sizes run into the same manifold (star), the 3/16" lines are running like hell, and the 5/16" lines seem to be full and the sap is not entering the mainline. Some of the drops are half filled with sap. It seems that the 3/16" lines are running so fast with so much pressure that the 5/16" lines can't drain into the same manifold. Anyone have an idea what is going on here?

[maple flats]

Yes you can and they will work well together as long as you have some slope on the main. The difference you are seeing with the 2 sizes is simply the difference between vacuum (on the 3/16) and no vacuum. When things really get going, both will flow.