Gets the pressure drop for the specified element id in this section. 
   Namespace:   Autodesk.Revit.DB.Mechanical  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 22.0.0.0 (22.1.0.0) 
  Since:  2013 
Syntax
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Parameters
- elemId
 -  Type:  Autodesk.Revit.DB ElementId  
The element id which can be duct segment, duct fitting , pipe segment and pipe fitting. 
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentException | The ElementId elemId does not correspond to a valid section member. | 
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was null |