When working with a Geometric Network, you have two options for constructing your model—if your model contains Complex Edges, then there is a distinct difference. A Complex Edge can represent a single feature in the Geodatabase, but multiple elements in the Geometric Network.

For example, when defining your Geometric Network, you can connect a lateral to a main without splitting the main line. In this case, the main line will be represented as a single feature in the Geodatabase but as multiple edges in the Geometric Network.

Depending on the data source type that you choose, ModelBuilder can see either representation. If you want to include every element in your system, choose ArcGIS Geometric Network as your data source type. If you want to leave out laterals and you want your main lines to be represented by single pipes in the model, choose ArcGIS Geodatabase Features as your data source type.