Introduction

EPANET is a Windows 95/98/NT program that performs extended period simulation of hydraulic and water-quality behavior within pressurized pipe networks. A network can consist of pipes, nodes (pipe junctions), pumps, valves and storage tanks or reservoirs. EPANET tracks the flow of water in each pipe, the pressure at each node, the height of water in each tank, and the concentration of a chemical species throughout the network during a simulation period comprised of multiple time steps. In addition to chemical species, water age and source tracing  can also be simulated.

The Windows version of EPANET provides an integrated environment for editing network input data, running hydraulic and water quality simulations, and viewing the results in a variety of formats. These include color-coded network maps, data tables, time series graphs, and contour plots.

EPANET was developed by the Water Supply and Water Resources Division (formerly the Drinking Water Research Division) of the U.S. Environmental Protection Agency's National Risk Management Research Laboratory. It is public domain software that may be freely copied and distributed.

EPANET provides a fully-equipped, extended period hydraulic analysis package which can:

• handle systems of any size 
• compute friction head loss using the Hazen-Williams, Darcy-Weisbach, or Chezy-Manning formulas 
• include minor head losses for bends, fittings, etc. 
• model constant or variable speed pumps 
• compute pumping energy and cost 
• model various types of valves including shutoff, check, pressure regulating, and flow control valves 
• allow storage tanks to have any shape (i.e., diameter can vary with height) 
• consider multiple demand categories at nodes, each with its own pattern of time variation 
• model pressure-dependent flow issuing from emitters (sprinkler heads) 
• base system operation on simple tank level or timer controls as well as on complex rule-based controls.

In addition , EPANET's water quality analyzer can:

• model the movement of a non-reactive tracer material through the network over time 
• model the movement and fate of a reactive material as it grows (e.g., a disinfection by-product) or decays (e.g., chlorine residual) with time 
• model the age of water throughout a network 
• track the percent of flow from a given node reaching all other nodes over time 
• model reactions both in the bulk flow and at the pipe wall 
• allow growth or decay reactions to proceed up to a limiting concentration 
• employ global reaction rate coefficients that can be modified on a pipe-by-pipe basis 
• allow for time-varying concentration or mass inputs at any location in the network 
• model storage tanks as being either complete mix, plug flow, or two-compartment reactors.

EPANET's Windows user interface provides a visual network editor that simplifies the process of building piping network models and editing their properties. Various data reporting and visualization tools are used to assist in interpreting the results of a network analysis. These include graphical views (time series plots, profile plots, contour plots, etc.), tabular views, and special reports (energy usage, reaction, and calibration reports).

EPANET was specifically developed to help water utilities maintain and improve the quality of water delivered to consumers through their distribution systems. It can be used to design sampling programs, study disinfectant loss and by-product formation, and conduct consumer exposure assessments. It can assist in evaluating alternative strategies for improving water quality such as altering source utilization within multi-source systems, modifing pumping and tank filling/emptying schedules to reduce water age, utilizing booster disinfection stations at key locations to maintain target residuals, and planning a cost-effective program of targeted pipe cleaning and replacement.

EPANET can also be used to plan and improve a system's hydraulic performance. Pipe, pump and valve placement and sizing, energy minimization, fire flow analysis, vulnerability studies, and operator training are just some of the activities that EPANET can assist with.