A constituent is any substance, such as chlorine and fluoride, for which the growth or decay can be adequately described through the use of a bulk reaction coefficient and a wall reaction coefficient. A constituent analysis determines the concentration of a constituent at all nodes and links in the system. Constituent analyses can be used to determine chlorine residuals throughout the system under present chlorination schedules, or can be used to determine probable behavior of the system under proposed chlorination schedules. To configure for a constituent analysis:

1. Click the Analysis menu and select Calculation Options.
2. In the Calculation Options manager, click the New button to create a new calculation option definition.
3. Change the Calculation Type to Constituent.
4. Specify the Calculation Times and the Constituent Tolerance. Optionally, specify Hydraulics, Adjustments, and/or Calculation Flag settings. Close the Calculation Options dialog.
5. Assuming you have not already set up a Constituent alternative for this scenario (including the selection of the constituent), go to the Alternatives tab, click the Ellipsis (...) or New button next to the Constituent scroll-down list, and add or edit a Constituent alternative (for more information, see Constituent Alternatives). To edit an existing alternative, click the Edit button. Enter the appropriate data, and click Close. Rename the alternative to give it a descriptive name. To add a new alternative, click the Add button. Enter a descriptive name into the New Alternative dialog box and click OK. Enter the appropriate data into the Constituent Alternative Editor and click Close. Specify the Constituent, which is defined in the Constituent Library and accessed by clicking the Ellipsis (...) button. Back in the Alternatives tab, choose the desired alternative from the Constituent Alternative choice list.
6. Click the Compute button.