Upon opening a Combination Pump Curve dialog, the user must first select which pump station is to be analyzed by either selecting one of the previously used pump stations from the drop down or picking the ellipse (...) button and selecting the station from the drawing.

Once the pump station has been selected, the dialog displays the possible pump combinations in the top left pane and the head curves in the bottom pane.

The column marked "Active" is checked if the user wants that combination displayed in the graph.

The column "ID" displays the index on the curve in the graph (e.g. Head[1] is the curve corresponding to the head of the pump combination with ID = 1).

There is one column in the table for each pump definition referenced in that pump station. The number in the cell indicates the number of pumps of that definition that are running for the combination corresponding to that row. If there is a zero in a cell, the pump is off for that combination.

The top middle pane determines which type of pump or system curve is displayed. By default, only the Head characteristic curve is displayed. The user can also turn on the (pump) efficiency or wire-to-water (overall) efficiency curves.

The system head curves are a property of the system calculated from the perspective of a pump. When the System Head Curve box is checked, the user must specify which pump is the Representative Pump which means which path through the station is head loss calculated. Usually the results don't vary significantly depending on which pump is selected.

The Maximum flow and Number of Intervals entries determine the horizontal extent of the system head curve and the number of points along the curve that will be calculated.

The top right pane is used to account for the fact that the system head curve will depend somewhat on the time of day. The user must select at least one time step to use in determining the system head curve. If the user selects a time step in which the pump is discharging into a closed system with no pressure dependent demands, the system head curve may show very high or low values for head. Do not select time steps where this occurs.

In order to run or rerun the pump combination graph, select the green Compute button at the top left of the bottom pane.

The graph below shows an example with three different combinations for two time steps (system head curves).

If the user wants to change the look of the graph such as the range of head values, use the second button in the bottom pane. That opens the graphing manager. To change the axis range, pick Chart > Axes > Left Axis > Maximum > Change and enter a new value. See ”Graphing’ for more details.