Pay close attention to logical controls, valve settings, and valve status, empty or full tanks, and near zero flows as these are common causes of the issue. (check the 'See also' for two links on this) Check general model setup If there are not validation issues, make sure the setup of elements are accurate. The Network Navigator tool can help you locate topological issues.

If your junctions are not connected properly you can use the Batch Pipe Split tool, which will allow you to connect the junctions to the pipes they are supposed to be connected to by splitting them. Nodes that are not connected to pipes can occur if you used ModelBuilder to create the model. If the element is a node, you can click and drag the element to make sure it is connected to all the pipes it is supposed to be connected to. Check the properties and setup of the element to see if there are issues related to data entry or orientation. If there are messages that are related to specific elements, double-click on it or right-click and choose 'Zoom To', which will select the element in the drawing pane. Perform a validation (Analysis > Validate) on the model to see if there is information on possible issues in the model. Solution Check Connectivity The first thing to do is to check to make sure your entire network is connected properly. If the program reaches the maximum number of trials without finding a solution, the 'Network Unbalanced' user notification is generated. If the relative flow change is greater than the Accuracy value, the program will try another iteration. If the relative flow change is below the 'Accuracy' value designated in the calculation options, the time step is balanced or is said to have converged. Between calculation iterations, the program checks the relative change in flow, which has a default value of 0.001. The difference between these is that the 'Network unbalanced' message can occur for individual time steps, while the 'Cannot solve network hydraulic equations' does not specify a time step where the issue occurs. Background The 'Network Unbalanced' and 'Cannot solve network hydraulic equations' user notification means that the program could not converge on a balanced solution within the maximum number of trials. A 'Reverse flow detected' may be encountered as well. Applies To Product(s): WaterGEMS, WaterCAD Version(s): 10.00.xx.xx, 08.11.xx.xx Area: Modeling Original Author: Scott Kampa, Bentley Technical Support Group Problem How can a user fix the WaterGEMS or WaterCAD error message ' Network Unbalanced ' or ' Cannot solve network hydraulic equations '.

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