You want to add a custom flow to a valve and assign it with a flow rate in increments such as gallons per minute (GPM).
You can assign a flow rate to a valve in one of two ways:
1. Add a cap to the project from Auxiliary Equipment. When you place the cap, the system will ask you to enter the pressure and flow for which you want it to stand in. You can then pipe that cap to a valve, size the laterals, etc.
2. Alternately, you can use a Schematic Area, which is particularly helpful if you don't know exactly how much pressure or flow to assign to the valve. For more information, see our Schematic Irrigation documentation section.
For more information on adding valves, see our Adding Valves to a Project page.