| Product(s): | SewerCAD, SewerGEMS |
| Version(s): | CONNECT Edition |
| Area: | Calculations |
Problem
When attempting to Validate or Compute a model with the GVF-Convex (SewerCAD) solver, the run fails and a user notification similar to the following appears:
"Gravity node upstream pressure pipe forms loop and may deliver water from downstream to upstream."
Solution
As the notification explains, this situation can occur if there is a loop in a pressure subnetwork where a pump is delivering water back to the upstream side of the same pump/wetwell. In large or complex models it can sometimes be difficult to locate the loop. A special query is available to help with this:
1) Go to View > Navigator (Network Navigator)
2) Click the ">" icon at the top, choose Network Trace and then select "Find Loops in Network"
3) A list of elements forming the loop should appear. Click the highlight button (blue pen icon) to highlight these elements, enabling you to zoom and perform other actions while still seeing the elements of interest.
You will need to fix the mistake or otherwise adjust the model to avoid forming loops, which would likely not be desirable in a real system anyways.
It may also help to make only the pumps and wetwells GIS style symbology, so that they stand out when zoomed out far enough to see the whole loop. This can be done by double clicking the pump and wetwell item form the Element Symbology manager, then in the properties window, select "GIS" for the "Display Style". Other element types can be left as CAD style for example with a suitably small symbol size.
Lastly, consider making the pressure pipe flow arrows larger, so that you can clearly see the flow direction when troubleshooting the highlighted loop. Double click pressure pipe in the Element Symbology list, choose "True" for "Show Flow Arrows" and either select GIS for the display style, or adjust the symbol size multiplier as needed.