OWA-EPANET Toolkit  2.2
Measurement Units

The toolkit can use data expressed in either US Customary of SI Metric units. A project's unit system depends on the unit system used for its choice of flow units. If the EN_open function is used to supply data to a project from an Input File then its flow units are set in the [OPTIONS] section of the file. If the EN_init function is used to initialize a project then the choice of flow units is the fourth argument to the function. The following table lists the units used to express the various parameters in an EPANET model.

Parameter US Customary SI Metric
Concentration mg/L or ug/L mg/L or ug/L
Demand (see Flow units) (see Flow units)
Diameter (Pipes) inches millimeters
Diameter (Tanks) feet meters
Efficiency percent percent
Elevation feet meters
Emitter Coeff. flow units @ 1 psi drop flow units @ 1 meter drop
Energy kwatt - hours kwatt - hours
Flow CFS (cubic feet / sec) LPS (liters / sec)
GPM (gallons / min) LPM (liters / min)
MGD (million gal / day) MLD (megaliters / day)
IMGD (Imperial MGD) CMH (cubic meters / hr)
AFD (acre-feet / day) CMD (cubic meters / day)
Friction Factor unitless unitless
Head feet meters
Length feet meters
Minor Loss Coeff. unitless unitless
Power horsepower kwatts
Pressure psi meters
Reaction Coeff. (Bulk) 1/day (1st-order) 1/day (1st-order)
Reaction Coeff. (Wall) mass/sq-ft/day (0-order) mass/sq-m/day (0-order)
ft/day (1st-order) meters/day (1st-order)
Roughness Coeff. millifeet (Darcy-Weisbach) unitless otherwise mm (Darcy-Weisbach) unitless otherwise
Source Mass Injection mass/minute mass/minute
Velocity ft/sec meters/sec
Volume cubic feet cubic meters
Water Age hours hours