problem in system curve in water gems

Question

i have two reservoirs ,junctions and one pump delivered water from R1 to R2 levels of it as flowing 
 junctions levels 
 Label Elevation (m) J-1 110.00 
 J-2 120.00 
 J-3 130.00 
 J-4 120.00 J-5 115.00 
 reservoirs levels 
 Label Elevation (m) R-1 100.00 R-2 110.00 
 pumps levels 
 Label Elevation (m) PMP-1 99.50 
 when i make run and open pump system curve i found water gems calculate when Q=0 H = 10 its difference between two reservoirs but H must me static head in water line calculated as ( max level in system - pump level ) in this example must be when Q=0 H=130-99.50=30.50 m system curve is very important in hydraulic analysis as its control flow in pipe and delivered head from pump

Tom Walski · Answer

The system head curve is the difference in head across the pump required to move water at the corresponding flow rate.

In the case when Q=0, the system head across the pump is 110 - 100 = 10 m.

See any hydraulics book for an explanation of this. It's page 45 of out Advanced Water Distribution System Modeling and Management book.

The elevation of the pump makes no difference in determining the system head curve (as long as you have adequate NPSH).

Jesse Dringoli · Answer

Regarding the high point at 130 m - you may need to insert an air valve there, and select "false" for "treat as junction". 
 
More on air valves here: 
 
 communities.bentley.com/.../23896.system-head-curve-with-intermediate-high-point 
 
 communities.bentley.com/.../2662.modeling-air-valves-at-high-points-in-watercad-or-watergems-tn 
 
More on System Head Curves here: 
 
 communities.bentley.com/.../24627.system-head-curves-in-watergems-and-watercad

Tom Walski · Answer

Just to clarify what happens when you have a intermediate high point. 
 
The downward sloping part of the pipe will generally be empty when you start the pump. You should calculate the system head curve from the suction reservoir to the high point (assuming you have an air release valve there which you should). Once the pipe is full, you calculate the system head curve for the entire pipeline. 
 
There are some exceptions. In some cases, the downward sloping pipe is so large and steep that it never runs full and the system head curve is always to the high point. 
 
The other case is the one where you don't have a air valve and the HGL at the high point drops below the vapor pressure of the fluid, which then vaporizes. You don't; want to have that happen. 
 
You need to make the downward pipe so small that it easily flows full or so large that it always flows partly full.