| Code | Meaning |
| 0 | No error |
| 101 | Insufficient memory available |
| 102 | No network data available |
| 103 | Hydraulic solver not opened |
| 104 | No hydraulics for water quality analysis |
| 105 | Water quality solver not opened |
| 106 | No results saved to report on |
| 107 | Hydraulics supplied from external file |
| 108 | Cannot use external file while hydraulics solver is open |
| 110 | Cannot solve network hydraulic equations |
| 120 | Cannot solve water quality transport equations |
|
| 200 | One or more errors in an input file |
| 201 | Syntax error |
| 202 | Function call contains an illegal numeric value |
| 203 | Function call refers to an undefined node |
| 204 | Function call refers to an undefined link |
| 205 | Function call refers to an undefined time pattern |
| 206 | Function call refers to an undefined curve |
| 207 | Function call attempts to control a check valve pipe or a GPV valve |
| 208 | Function call contains illegal PDA pressure limits |
| 209 | Function call contains an illegal node property value |
| 211 | Function call contains an illegal link property value |
| 212 | Function call refers to an undefined Trace Node |
| 213 | Function call contains an invalid option value |
| 214 | Too many characters in a line of an input file |
| 215 | Function call contains a duplicate ID label |
| 216 | Function call refers to an undefined pump |
| 217 | Invalid pump energy data |
| 219 | Illegal valve connection to tank node |
| 220 | Illegal valve connection to another valve |
| 221 | Mis-placed clause in rule-based control |
| 222 | Link assigned same start and end nodes |
| 223 | Not enough nodes in network |
| 224 | No tanks or reservoirs in network |
| 225 | Invalid lower/upper levels for tank |
| 226 | No head curve or power rating for pump |
| 227 | Invalid head curve for pump |
| 230 | Nonincreasing x-values for curve |
| 231 | No data provided for a curve |
| 232 | No data provided for a pattern |
| 233 | Network has unconnected nodes |
| 240 | Function call refers to nonexistent water quality source |
| 241 | Function call refers to nonexistent control |
| 250 | Function call contains invalid format (e.g. too long an ID name) |
| 251 | Function call contains invalid parameter code |
| 252 | Function call rferes to an invalid ID name |
| 253 | Function call refers to nonexistent demand category |
| 254 | Function call refers to node with no coordinates |
| 255 | Function call refers to link with no vertices |
| 257 | Function call refers to nonexistent rule |
| 258 | Function call refers to nonexistent rule clause |
| 259 | Function call attempts to delete a node that still has links connected to it |
| 260 | Function call attempts to delete node assigned as a Trace Node |
| 261 | Function call attempts to delete a node or link contained in a control |
| 262 | Function call attempts to modify network structure while a solver is open |
| 263 | Function call refers to node that is not a tank |
| 264 | Function call refers to a link that is not a valve |
| 299 | An invalid section keyword was detected in an input file |
|
| 301 | Identical file names used for different types of files |
| 302 | Cannot open input file |
| 303 | Cannot open report file |
| 304 | Cannot open output file |
| 305 | Cannot open hydraulics file |
| 306 | Hydraulics file does not match network data |
| 307 | Cannot read hydraulics file |
| 308 | Cannot save results to binary file |
| 309 | Cannot save results to report file |