IRRICAD is telling you that the incoming flow or pressure does not equal the outgoing flow or pressure at a junction or outlet.
Check things like:
- control valve data in the database
- multiple water supplies - pressures and flows should be slightly different from each other
- water supply times do not overlap if the water supplies are supplying totally separate hydrants
- check the management - that mainline outlets and control valves are being supplied by the water supply they are attached to.
If a network imbalance does occur, check the reports (inflows and outflows). If the imbalance is minimal it can be ignored. If it is significant, IRRICAD has become confused (if multiple water supplies) or there are 'leaky pipes' - something in the system which is allowing the imbalance. Try simplifying the system until you find the problem.
This error can sometimes be fixed by reducing the "Mainline Analysis factor" in Design|Design Parameters|Analysis Parameters. It usually indicates the system is extremely unbalanced hydraulically - caused by wrong elevations or valves or outlets or pumps or something in the design.