I bought a surplus chemlawn hippo and I have been having a great time rebuilding the plumbing system. I am having trouble with the bypass system. It splits into two - one bypass goes to the top of the tank and discharges, the other connects to a pipe that goes to the bottom of the tank, forks into four pipes with venturi nozzles at each end. The two bypass lines connect at the top of the tank through a pressure regulator. We've rebuilt the regulators (all five of them) rebuilt the two pumps and are satisfied that they work. All we can get the system to do is to discharge through the top, not through the venturis. What am I missing here?