Analysis and Design of Distribution Systems for Potable Water

using the EPANET model

Part 2

Modern pipe network models–Kypipes–WaterCAD–CyberNET–EPANET

www.epa.gov/ORD/NRMRL/wswrd/epanet.html

EPANET• performs extended period simulation of hydraulics

and water quality within pressurized pipe networks.• A network can consist of:– pipes– nodes (pipe junctions)– pumps– valves – storage tanks – reservoirs

• EPANET computes at each timestep– flow in each pipe– pressure at each node– height of water in each tank or reservoir, – water “age” (residence time) – concentration of each water quality parameter

EPANET Applications

• Design to ensure adequate flow and pressure– tank elevations and sizes– pipe sizes– size and location of pumps to ensure

• assessment and management – use of alternative sources within multiple source

system – cost of various pumping schedules – Schedule pipe cleaning and replacement

Hydraulic Modeling Capabilities

– Computes friction head loss using either Hazen-Williams, Darcy-Weisbach, or Chezy-Manning equations.

– Includes minor head losses for bends, fittings, etc.

–Models constant or variable speed pumps.– Computes pumping energy and cost.–Models various types of valves including

shutoff, check, pressure regulating, and flow control valves

EPANET model components --links connected to nodes. Links: pipes, pumps, and control valves. Nodes: junctions, tanks, and reservoirs

Steps in Using EPANET

1. Set program defaults (naming convention, pipe roughness, unit system, head loss formula)

2. Draw the distribution system (Section 6.1 in manual) by inserting nodes and connecting with links; underlay a graphic if desired

3. Edit the properties of the objects that make up the system (Section 6.4), eg, pipe length and diameters, nodal elevations

4. Describe how the system is operated (Section 6.5) 5. Select a set of analysis options (Section 8.1) – timestep,

duration6. Run hydraulic/water quality analysis (Section 8.2) 7. View results (Chapter 9)8. Change parameters and repeat as necessary

Program User Interfacemap toolbar

browser (data and map tabs)

propertyeditor

Project Setup

View >> OptionsProject >> Defaults

Creating Network using tools on map toolbar

Connect nodes with pipes,add pumps, valves and labels

Use the map tab of the browser to color-code nodes and pipes according to different properties

Set properties for nodes (junctions) and pipes.

First, chose category of objectfrom the data browser

Then double click in list or on map to select

Click “Add” icon to create a new object of current category

Set properties for nodes (junctions) and pipes

These will be filled in after you run a simulation

For junctions, minimum requiredinformation is demand andelevation.

Set properties for nodes (junctions) and pipes

These will be filled in after you run a simulation

• For pipes, minimum requiredinformation is start and end nodes, lengths, diameters, and roughness.

Set properties for tanks, reservoirs and pumps

Pump Curves

Set properties for tanks

Minimum information is elevation, a diameter, a minimum, maximumand an initial water level.

Sign on flow indicates direction relative to flow arrow on the map.

This allows you to vary nodal demands throughout the day

View results on the map

Common errors/warnings• “Network is disconnected”

No connecting/open link to all nodes with demands. • “Hydraulic equations unsolvable”

Network is disconnected or unrealistic values specified for network properties.

• “Pumps cannot deliver flow or head” Pump asked to operate outside range of characteristic curve; turned off if asked to deliver head greater than shutoff head.

• “System unbalanced” EPANET cannot converge; can occur if pumps turn on/off or valves open/close from trial to trial.