Wastewater pump stations dot the landscape of almost every wastewater reticulation network across New Zealand. Typically their design, location at key nodes within the reticulation and the presence of the data logging capabilities of modern onsite SCADA systems make them tempting locations for flow measurement via the method of inflow computation.

The flow measurement information can be a critical input into network modeling, consent compliance, operational control and event trouble-shooting.

However, logged data on SCADA, even if it is verified, and applying one of several different methods for inflow calculation does not always result in a data set that is accurate, that truly reflects reality at key times or is reality usable for modeling.

This paper will highlight several limitations present with computing inflow data from pump status and wetwell records and will provide practical solutions to overcome them. These limitations can have a significant influence on the ease and accuracy of subsequent modeling and the use of the data for other purposes.