The calculated pressure drop of this pump is not computed because the critical path is not a closed loop. Check to see if there are other pumps intended for use within a secondary/tertiary loop. Use the Add Separation tool to define the secondary/tertiary loop. 
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 24.0.0.0 (24.0.0.0)
Syntax
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