Some terms used in flushing are explained below:

• Event refers to a single operation of a flowed hydrant(s) with any associated valve operation. It corresponds to a single steady state simulation with a flowed hydrant(s). Events may be conventional or unidirectional.
• Conventional event refers to opening a single hydrant with no associated valve operation (valves are set according to the representative scenario). A user selects a set of flushing nodes (hydrants or junctions). Each of these nodes are treated as separate events, making it very easy to set up a large number of conventional events (as opposed to the more detailed steps needed for unidirectional flushing). The user may wish to quickly assess the performance of conventional flushing as a first step before moving to unidirectional flushing.
• Unidirectional flushing (UDF) refers to flushing where isolation values (or pipes) may be closed and more than one hydrant may be flowed. UDF can generate higher velocities and shear stress. The goal is to reach high velocity in a series of pipes referred to as a Pipe Run which is specified to each UDF event. The user can compare with conventional flushing to determine if the additional effort is justified.
• Pipe run refers to the collection of pipe links that a user wishes to flush in a UDF event. The volume of water in the pipe run is used as the minimum amount of water that must be flushed and the time to flush that volume is used as the minimum time of flushing. A pipe run should consist of pipes in series from the flowed hydrant. There is no pipe run for a conventional event since flow direction cannot be controlled. Pipes in a pipe run should also be part of the pipe set (see below) for an area.
• Flushing Area (or Area) refers to a set of flushing events that are usually focused on a given portion of the system. By computing an area, every event in that area is simulated. An area is associated with a single representative scenario which controls boundary conditions. An area might consist of a neighborhood to be flushed or a collection of events that can be run by a crew in a single shift. In general flushing areas should not significantly overlap.
• Pipe set refers to the pipes that the user wants to flush in a given area. These are the pipes considered when determining properties like "Pipe length met target". The Pipe set should encompass all pipe runs in the area. A pipe set is a required input. It is created by picking the ellipse button next to pipe set. It is advisable to create a selection set corresponding to each pipe set before starting the flushing manager. These can be useful for reviewing results.
• Nodes of Interest are nodes for which auxiliary results are saved. These are useful for monitoring nodes than may have low pressure during flushing. Nodes of interest are an optional input.
• Flowed elements can be either junction nodes or hydrant nodes. For conventional flushing with no valve closure, hydrants are generally close enough to nodes that the results are virtually the same. However, in UDF where a valve may be closed between the hydrant and junction, it is important to represent the location of the flowed hydrant explicitly in the model.
• Controlled (Closed) elements can be represented either by a closed isolation valve or a closed pipe element in UDF. (There are no closed elements in conventional flushing.) Closing an isolation valve is a more precise way of modeling UDF but some models do not contain isolation valves. When a pipe element is closed, it is assumed that an operable valve is present. A closed pipe cannot be part of a pipe run.
• Flushing study refers to a group of areas that possibly cover the entire system. Computing a study will run all of the events in all of the areas in the study. A set of studies may be used to compare different approaches to flushing a system. One study may rely heavily on conventional flushing while another may rely on UDF. There needs to be at least one study with at least one area containing at least one event.
• Representative scenario refers to the existing scenario that established the boundary conditions and demand that relate to a flushing area. This determines which pumps are operating, what the demands are and what tank levels are set to during the flushing analysis. These should be steady scenarios. If they are EPS scenarios, then the zero time is used unless the user specifically sets a time.
• Output scenario is the name given to the scenario that contains the results of the flushing analysis. There is one output scenario per area and the current scenario should be set to the output scenario to view results in the flushing result browser once the user leaves the flushing manager.