| Applies To | |
| Product(s): | SewerCAD, WaterCAD, WaterGEMS |
| Version(s): | 10.00.xx.xx, 08.11.xx.xx |
| Area: | Modeling |
| Original Author: | Scott Kampa, Bentley Technical Support Group |
The calculated system head curve contains negative head values for low flow situations. Why is this occurring?
Problem ID#: 72750
The negative head value for the system head curve occurs because of the elevations at the boundaries in the system.
If the boundary downstream of the pump has a lower elevation value that the upstream boundary, negative values for head are possible in zero or low flow situations. This is because the no pump flow is needed to overcome the change in elevation. You many want to review the elevations in the model. If you have an air valve at high points, you may want to very that the attribute "Treat Air Valve as Junction?" is set to False. Then the program will use the air valve high point as the boundary to calculate the system head curve and you will likely see positive values in the system head curve.
Understanding System Head Curves in WaterGEMS, WaterCAD, and SewerCAD