Why are my GPM readings zero?

I see reasonable looking pump starts and runtimes for both pumps, why are my GPM readings zero?

Let's look at the clues...

  • runtimes and starts for both pumps were identical
  • the starts ratio was always 1.0
  • "hours with two pumps running" figure exactly matched the value of runtime for either pump

In this scenario, the most likely cause of the zero GPM readings is that pump inputs 1 and 2 were seeing the same input conditions. This likely would be due to a problem with shorted inputs. Alternatively, there could be a signal problem with pump controller or a problem with the float switches that would make it appear as though the pump inputs are being shorted.

As a side note about GPM with two pumps running:

The pump performance algorithm is designed to ignore statistical periods when two pumps are running. A well designed lift station is assumed to have few pump cycles when both pumps are needed to pump out the wet well. GPM can only be calculated for normal or "typical" pump cycles.