One primary purpose of a UDF program is to determine how to raise the pipe flow velocities high enough to scour (clean) the pipe walls. Operating fire hydrants is the primary method of changing pipe flow velocities, and thereby are the instrument by which water can exit from the system (removing built-up particles, debris, and water with "bad" quality.) Opening a typical fire hydrant by itself does not typically cause a large enough increase in water velocity to engender the desired effects. Judicious selection of valves to close, to result in a more direct (less looped) flow path to the flowing hydrant results in velocities high enough to scour pipe walls.

Flush sequences are used to define how each zone will be flushed. The goal is to start from a clean water source (i.e., pump station or previously flushed sequence), select a hydrant to be flushed, and determine which valves are necessary to close to increase the water velocity such that it exceeds the minimum flushing (scouring) velocity in the pipes leading to the hydrant. The hydrant must remain open for at least the time necessary to turn over the water in the pipe(s) being flushed - this is referred to as the minimum flushing time. For each flush sequence there are several important hydraulic criteria, including:

  • Maintaining a minimum pressure inside the distribution system

  • Minimizing the volume of water used

  • Ensuring that water that has not yet been flushed does not get routed through a previously flushed area.

InfoWater UDF details when the characteristics were not achieved by a flush sequence by issuing warnings.

The Flush Sequence Manager is used to specify sequencing and view sequence results within a flush zone. Press from the UDF toolbar to open the Flush Sequence Manager.