Subject: The Importance of Viewing Results at the Proper Time Scale
In SWMM 5 when you are simulating rapidly changing flow – such as pump flows – it is important to remember that you are only seeing the results of the simulation at your selected report time step. Here is an example model with the same number of pump starts for all three simulations (318), the same average time step during the simulation (10 seconds) but different report time steps. The conception of the pump starts is totally different visually depending on the selected report time steps. You should always compare the starts using the pump graphs and the pump summary table. The percent utilized and the number of pump start ups tells you the mean pump start length or in this case 153 seconds or 45.1 percent of 30 hours divided by 318 pump starts.