You are currently reviewing an older revision of this page.
I have PRVs in parallel at one location in my model and I am getting a user notification that states my network is unbalanced when I compute. In the field both PRV's are active at the same time. When I only run the system with one PRV the model computes fine. How can I resolve this?
If the PRV's that are in parallel are set to an initial hydraulic grade or pressure setting that are close to each other then what might be happening is the calculation engine would be trying to reduce the pressure downstream to one hydraulic grade and then the other, which causes the results to toggle back and forth because it can't settle on a result as to what the pressure should be.
Combine the PRV's into a single PRV that uses a hydraulic grade or pressure setting that is an average of the two PRV settings. Then you could consider increasing the size of the pipe directly connecting to the upstream and downstream side of the PRV (for example double the diameter).
If you'd still like to keep both PRV's in your model you could choose either the higher initial setting, lower initial setting, or a setting that is an average of both (as in example one) and just assign that initial setting to both valves. This is similar to option 1 because we are assuming that downstream of these PRV's where the pipes converge there is some average of the hydraulic grade (pressure).
In recent versions, the ability to use the WaterGEMS 2.0.12 numerical solver version is available, which has some enhancement specific to this type of situation. If you are not already using it, set the Engine Compatibility calculation option to version 2.0.12 and try adjusting the new additional calculation options that are exposed.
Engine Compatibility Modes and related Calculation options