The total pressure loss of the section. 
   Namespace:   Autodesk.Revit.DB.Mechanical  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2013 
Syntax
Remarks
 It's total of all fittings and segments. Default unit is Kgf per square feet. For Duct, unit type is UT_HVAC_Pressure. For Pipe, unit type is UT_Piping_Pressure.