picking submersable pump/ calculating resistance from a long run of water pipe
I have a cistern fed by a spring and there is a submersable 4" 220 v pump in it. It is located a long way from my house. The water is pumped a little over a 1/4 mile through 1 1/4 " galvanized pipe. There is probably only 60 foot elevation rise. The pump needs to be replaced and I am wondering how to calculate the resistance of the water through the pipe in with sizing the pump. I have a barn halfway to the house with water. Currently, at 60 psi showing onthe pressure guage, water will flow at the barn, but not at the house. At 90 psi it flows well at the house also. I don't know what size/stage pump is in the cistern right now.
As an aside, I was considering a constant pressure type pump, as the water volume at the house does vary cosiderably as the pressure tank drains/system cycles- anyone have any experience with them?