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Screen of Network Map from EPANET

Model for Water Distribution Piping Systems


EPANET is software that models drinking water distribution piping systems. EPANET is public domain software that may be freely copied and distributed. It is a Windows 95/98/NT/XP program. EPANET performs extended period simulation of the water movement and quality behavior within pressurized pipe networks. Pipe networks consist of pipes, nodes (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 the water in each tank, the type of chemical concentration throughout the network during a simulation period, the age of the water, and source tracing.

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EPANET's Windows user interface provides a visual network editor that simplifies the process of building piping network models and editing their properties and data. EPANET provides an integrated computer environment for editing input data. Various data reporting and visualization tools are used to assist in interpreting the results of a network analysis, including color-coded network maps, data tables, energy usage, reaction, calibration, time series graphs, and profile and contour plots.

EPANET's  fully equipped, extended-period hydraulic analysis package can do the following:

  • Simulate systems of any size
  • Compute friction head loss using the Hazen-Williams, the Darcy Weisbach, or the Chezy-Manning formula
  • 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
  • Account for any shape storage tanks (i.e., surface area can vary with height)
  • Consider multiple demand categories at nodes, each with its own pattern of time variation
  • Model pressure-dependent flow issuing from sprinkler heads
  • Base system operation on simple tank level, timer controls or complex rule-based controls

EPANET's water quality analyzer can be used for the following:

  • 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) over 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 complete mix, plug flow, or two-compartment reactors

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EPANET helps water utilities maintain and improve the quality of water delivered to consumers. It can be used for the following:

  • Design sampling programs
  • Study disinfectant loss and byproduct formations
  • Conduct consumer exposure assessments
  • Evaluate alternative strategies for improving water quality
  • Modify pumping and tank filling/emptying schedules to reduce water age
  • Use booster disinfection stations at key locations to maintain target residuals
  • Plan and improve a system's hydraulic performance
  • Assist with pipe, pump, and valve placement and sizing
  • Energy minimization
  • Fire flow analysis
  • Vulnerability studies
  • Operator training

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Programmer's Toolkit

The EPANET Programmer's Toolkit is a dynamic link library (DLL) of functions that allow developers to customize EPANET to their own needs. The functions can be incorporated into 32-bit Windows applications written in C/C++, Delphi, Pascal, Visual Basic, or any other language that can call functions within a Windows DLL. There are over 50 functions that can be used to open a network description file, read and modify various network design and operating parameters, run multiple extended-period simulations accessing results as they are generated or saving them to file, and write selected results to a file in a user-specified format.

The toolkit is useful for developing specialized applications, such as optimization or automated calibration models that require running many network analyses. It can simplify adding analysis capabilities to integrated network-modeling environments based on computer-aided design (CAD), geographical information system (GIS), and database packages. A Windows Help file is available to explain how to use the various toolkit functions. It offers some simple programming examples. The toolkit also includes several different header files, function definition files, and .lib files that simplify the task of interfacing it with code.

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Multi-Species Extension

EPANET-MSX (Multi-Species eXtension) enables EPANET to model complex reaction schemes between multiple chemical and biological species in both the bulk flow and at the pipe wall. This capability has been included into both a stand-alone executable program as well as a toolkit library of functions that programmers can use to build customized applications. EPANET-MSX allows users the flexibility to model a wide range of chemical reactions of interest. Examples include 

  • the auto-decomposition of chloramines to ammonia,
  • the formation of disinfection byproducts,
  • biological re-growth including nitrification dynamics,
  • combined reaction rate constants in multi-source systems, and
  • mass transfer limited oxidation-pipe wall adsorption reactions.

EPANET-MSX is distributed in a compressed zip file that contains a command line executable, several libraries of functions, and a User’s Manual. The executable can be used to run water quality analyses without any additional programming effort. The function library can be used in conjunction with the EPANET Programmer’s Toolkit to develop customized applications. At this point in time, the software has not been integrated into a Windows interface.

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EPANET files may be freely downloaded, copied, and distributed.
Date File Description
3/5/08 Self-extracting installation program for EPANET 2.00.12 (EXE)(2 MB)  (1.5 MB)
9/11/00 EPANET 2 Users Manual (PDF) (200 pp, 1 MB, See EPA’s About PDF page to learn more.)
3/20/08 EPANET 2 Programmer’s Toolkit files (ZIP)(253 K)  (247 KB)
5/27/08 EPANET 2 source code files (ZIP)(566 K)  (553 K)
2/25/08 EPANET 2 Updates(22 K)  (22 K)
5/7/08 Multi-Species Extension

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Technical Contact

Contact us with comments or questions about EPANET.