I've watched the sap coming in the laterals to my manifold and seen the same thing. Especially in the morning when the trees first thaw and start running. Another thing that compounds this is having laterals with varying amounts of taps and obviously length. Part of the fluid dynamic is the equilibrium finding itself an all of that tubing. Even though some of the laterals have more taps, they may have more space in between each tap. There's constant change inside that system as some of the trees produce more sap and some produce more gas. After an hour or so of the trees running, the equilibrium is pretty much constant, and the surging seems to diminish, until the tress and laterals start to freeze in the evening, you'll see the same thing again. Get the leaks in the tubing and the manifold fixed and like you said, you'll be looking for ways to store/boil more sap!! I've been running four to five shurflo 4008's for five years now, no recirc lines, and this year I let them run 24/7 on days with a good flow forecast. I added another 100 watt panel to each system 300 watts total now, and with the strainer screen in place, you won't have any ice damaging the diaphragms. I bought inkbirds last year and still haven't got them wired up. I haven't had to swap a battery all year with 300 watts running into my 15 amp charge controllers. I had to clean my strainers 2x a day a few wees ago with the 65F days we had back to back. That sure slimes up the lines in a hurry.