The water loop element id for the hot-water heating coil. 
   Namespace:   Autodesk.Revit.DB.Mechanical  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 21.0.0.0 (21.1.1.109) 
  Since:  2020.1 
Syntax
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | When setting this property: A non-optional argument was NULL |