I have a pump that connects to the users and to one tank. The idea is that when the tank has low water it will receive water, and when the tank has high water level it will provide water (during high demand).
I am using this pump

1000 GPM, 280 ft, 125 HP, Max WP 175 psi, 1800 RPM, D 17"

However, the pump only provides 7 GPM, very low considering that is can provide 1000 GPM.
I provided this NSPH curve:
1000 GPM - 10 ft
1500 GPM - 16 ft
1800 GPM - 22 ft

I tried:
i) Constant power 125
ii)Design point. Design head 280ft, Design Flow 1000 GPM
iv) Multiple point curve
0 GPM 290 ft
1000 - 280
1500 - 250
1800 - 220

Why is the pump giving so little water?
If I close the pipe of the Tank the simulation fails unbalanced error.Pump.jpg