Curve

Pump Curve

A Pump Curve represents the relationship between the head and flow rate that a pump can deliver at its nominal speed setting.

• Head is the head gain imparted to the water by the pump and is plotted on the vertical (Y) axis of the curve in feet (meters). Flow rate is plotted on the horizontal (X) axis.
• A valid pump curve must have decreasing head with increasing flow.
• EPANET will use a different shape of pump curve depending on the number of points supplied:
  
  

  A single-point pump curve is defined by a single head-flow combination that represents a pump's desired operating point. EPANET fills in the rest of the curve by assuming: a shutoff head at zero flow equal to 133% of the design head a maximum flow at zero head equal to twice the design flow.
  A three-point pump curve is defined by three operating points : Low Flow (flow and head at low or zero flow condition) Design Flow (flow and head at desired operating point) Maximum Flow (flow and head at maximum flow). EPANET fits a continuous function through the three points to define the entire pump curve.
  A multi-point pump curve is defined by providing either a pair of head-flow points or four or more such points. EPANET creates a complete curve by connecting the points with straight line segments.
  A constant power pump is a pump that operates at a constant horsepower or kilowatt rating over all combinations of flow and head. The user only needs to supply the pump's power rating.

Efficiency Curve

An Efficiency Curve determines pump efficiency (Y in percent) as a function of pump flow rate (X in flow units). Efficiency should represent wire-to-water efficiency which takes into account mechanical losses in the pump itself as well as electrical losses in the pump's motor. The curve is used only for energy calculations. If not supplied, then the global pump efficiency (a single number) in the project's Energy Options is used instead.

Volume Curve

A Volume Curve determines how storage tank volume (Y in cubic feet or cubic meters) varies as a function of water level (X in feet or meters). It is used when it is necessary to accurately represent tanks whose cross-sectional area varies with height. The lower and upper water levels supplied for the curve must contain the lower and upper levels between which the tank operates. An example of a tank volume curve is given below.

Head Curve

A Head Loss Curve is used to described the headloss (Y in feet or meters) through a General Purpose Valve (GPV) as a function of flow rate (X in flow units). It provides the capability to model devices and situations with unique headloss - flow relationships, such as reduced flow backflow prevention valves, turbines, and well drawdown behavior.