System curve for water line discharging above water surface

Hi Patrick

I finally have a bit more time to look into my modeling issues and I have come up with a combination tank/vsp/pumped system question. I have a few pumped pressure zones in the municipal system. One of them is a well (2 VS pumps in an old mineshaft) that discharges into a closed pipe system and a storage tank supply pipe. The well pumps manifold together and subsequently split with one pipe supplying a small pumped pressure zone (avg demand less than 15 gpm) and the remainder heads up about 230' vertically uphill where it empties into a 2.5 mg storage tank and pressurizes a different pressure zone. The tank's pipe entry is about 5 or 6 feet above the water surface in the tank and it free falls into the tank. The tank puts no head pressure on the supply line from the well pumps, but the line has check valves and it does have the pressure of the full pipe the whole way up the hill. Basically the well pumps are split to supply the pressure zone and the tank, and the pumps run all the time, maintain line pressure about 125psi (the head of the tank supply line). When supply exceeds demand, the proxy pressure reducing valve is the free surface entry into the tank, so when supply outstrips demand the remainder of the well water pumped simply fills the tank. The well pump pressures are not monitored as the tank pipe entry acts to reduce excessive pressure and so there is no problem with over pressuring the small pumped pressure zone. I am getting negative pressures at the high point of the tank supply pipe that do not allow the model to run properly.

Any idea the best way to model this one? the free drop into the tank? The previous advice you guys have been giving has been spot on. This model is starting to get a bit frustrating and have already dumped considerable time effort and consultant dollars in to it to no avail. Thanks in advance for any and all input, I have to be out in the field for a while today, so I might not be able to respond right away. Thanks Jamie