| Code | Description |
| 1 | System hydraulically unbalanced - convergence to a hydraulic solution was not achieved in the allowed number of trials |
| 2 | System may be hydraulically unstable - hydraulic convergence was only achieved after the status of all links was held fixed |
| 3 | System disconnected - one or more nodes with positive demands were disconnected from all supply sources |
| 4 | Pumps cannot deliver enough flow or head - one or more pumps were forced to either shut down (due to insufficient head) or operate beyond the maximum rated flow |
| 5 | Valves cannot deliver enough flow - one or more flow control valves could not deliver the required flow even when fully open |
| 6 | System has negative pressures - negative pressures occurred at one or more junctions with positive demand |