Warning messages include:

1. Some rows were ignored due to missing key-field values. - ModelBuilder encountered missing data (e.g., null or blank) in the specified Key/Label field for rows in your data source table. Without a key, ModelBuilder is unable to associate this source row with a target element, and must skip these items. This can commonly occur when using a spreadsheet data source. To determine where and how often this error occurred, check the Statistics page for the message <x> row(s) ignored due to missing key-field values.
2. Unable to create pipe <element>; start and/or stop node could not be found. - Pipes can only be created if its start and stop nodes can be established. If you are using Explicit connectivity, a node element with the referenced start or stop label could not be found. If you are using implicit connectivity, a node element could not be located within the specified tolerance. For more information, see "Specifying Network Connectivity in ModelBuilder"-195.
3. Unable to update pipe <element> topology; (start or stop) node could not be found. - This error occurs when synchronizing an existing model, and indicates that the pipe connectivity could not be updated. For more information, see warning message #2 (above).
4. The downstream edge for <element> could not be found. - ModelBuilder was unable to set a Pump direction because a pipe with the referenced label could not be found.
5. Directed Node <element> direction is ambiguous.
6. ModelBuilder was unable to set the direction of the referenced pump or valve because direction could not be implied based on the adjacent pipes (e.g. there should be one incoming and one outgoing pipe).