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I am trying to represent a pump that I do not have a pump curve for. I have one person advocating for simply using a negative demand but I am afraid this won't capture the actual pump performance as determined by the system conditions that will vary. Rather, I am thinking it would be more appropriate to use a one point design curve that has been somewhat "calibrated" to match hydrant tests/system pressures. Which would be the correct or more accurate way to do this in WaterCAD?
As my colleague Tom suggested in his response, having actual data is the best possible way to setup your model and analyze it. This would ensure that the results generated are as close to the real values observed on field.
Setting up a study with a rough estimate of the pump head and discharge is one way to check if the results comply with your assumption. However, you would need the total head and discharge from the pump to setup a single design point pump curve.
The approach to setup a negative demand is generally used when you only know the flow required from the pump. After setting it up the head required by the pump would be the difference in the hydraulic grades between the two nodes. See the article below for reference on this;
Estimating a pump curve for a model
Additionally we do have more such articles which can guide you into selecting a pump curve and comparing it with a system head curve.
How to manually generate a system head curve?
Understanding System Head Curves in WaterGEMS, WaterCAD, and SewerCAD
General Pump Selection Process
Hope this helps.
Bentley Technical Support
Thank you both for the responses!