Common Mistakes and Troubleshooting

Common Mistakes and Troubleshooting

Based on requests for support made by DRAINS users, the most common causes of errors are:

Failure to attend to matters raised in warning messages.

As well as checking for obvious data entry errors, DRAINS provides warnings both before and after runs.  Users often disregard these warning messages and press on with runs, leading to instabilities in hydraulic calculations and incorrect results. You should aim to eliminate error messages so that the run log is clear of warnings.

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Increasing time steps

DRAINS sets calculation time steps to keep calculations stable. These can be decreased (to a minimum of 0.001 minutes) to provide more stable results, but it  is dangerous to increase time steps.

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Using unrealistic dimensions of components

Obviously, users must provide correct dimensions for most components, but there are some that can be loosely defined, such as overflow routes that are used mainly to move flows between components.  If these are too unrealistic, however, there can be problems such as instabilities and incorrect HGL levels.  The way that you set up models should follow real systems as much as possible.


Troubleshooting Tips

If a model will not run from the Run menu, check for components that have not been fully defined, or which are not properly connected to other components.  The Find ????? option in the Edit menu can be used to find these. Provided that the Main Window is not zoomed-out too far, DRAINS will move the model in the Main Window so that an unconnected or incompletely-specified component is located in the top left corner of the window.  Correct these and the model should run.

If you make a run but there are no flows, it could be that the hydrological losses are higher than the rainfalls and there is no runoff. Check  that the losses are correct, and compare them to the rainfalls.

Do not make judgments solely on the coloured numbers that appear in the Main Window.  Examine charts and tabular results as well. If DRAINS runs but gives results that are unstable, with flowrates and HGL levels fluctuating strangely, try reducing the time steps in the Project Options property sheet. 

Results that appear to be wrong, with conflicting flowrates or water levels, may be due to  the numbers coming from different storms.  When troubleshooting, run only one storm at a time. It is then a lot easier to compare results for adjoining components, and to see whether there are inconsistencies.

 


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