Building a network

Add and edit junctions, reservoirs, tanks, pipes, pumps and valves; set sensible defaults; and keep units straight (LPS, metres, millimetres).

Pick units before you draw

EPANET has no separate unit setting. Every unit in the project follows from one choice, Flow Units, in Project > Analysis Options... on the Hydraulics page. Choose a metric flow unit and the whole project is metric:

Quantity	Metric flow units (LPS, LPM, MLD, CMH, CMD)	US flow units (GPM, CFS, MGD, IMGD, AFD)
Flow and demand	the flow unit chosen, for example LPS	the flow unit chosen, for example GPM
Elevation, head, length, tank levels	m	ft
Pipe diameter	mm	in
Pressure	m (metres of water)	psi
Velocity	m/s	ft/s
Unit headloss	m/km	ft/kft
Tank volume	m3	ft3
Pump power	kW	hp

For Indian work, LPS is the usual choice: demands come out in litres per second, pressures in metres (the unit CPHEEO norms use) and diameters in millimetres.

Why units matter

A diameter is read in the project's units. In an LPS project, a pipe diameter of 6 means 6 mm, not 6 inches. The pipe is about 25 times too narrow and the run shows huge headlosses or negative pressures. A 6 inch pipe is 152 mm.
Pressures are compared with norms in metres. CPHEEO residual pressures are in metres. In a GPM project the Property Editor reports psi.
Defaults follow the numbers, not the units. EPANET's own default pipe is 1000 long and 12 across. In a GPM project that is 1000 ft of 12 inch pipe; in an LPS project it would be 1000 m of 12 mm pipe. Set metric defaults (below) when you work in LPS.

Project > Model Check... warns when diameters in a metric model look like inches (48 or less), and when a US model has diameters that look like millimetres.

If you change Flow Units between a US and a metric unit after building a network, EPANET converts every stored value (elevations, lengths, diameters, demands, tank sizes, curves) so the network stays physically the same, and PipePilot moves the pressure unit with it. That is right when the network was entered correctly in the old units. It is wrong when the numbers were typed in metric while the project was still in GPM: in that case fix the units first, before entering data, or correct the values afterwards.

Set defaults for new objects

Open Project > Defaults.... The Properties tab sets what every new object starts with:

Default	A sensible metric start	Why
Node Elevation	0, then enter real levels	There is no safe default for ground level. Enter it for every node from survey or a DEM.
Tank Diameter, Tank Height	10 m and 5 m	About 390 m3, a small ESR. Edit each tank to its real size.
Pipe Length	100 m	A street block is often 80 to 150 m. Or turn on Auto Length.
Pipe Diameter	150 mm	A common distribution main, above the 100 mm CPHEEO minimum for primary pipes.
Pipe Roughness	140 (Hazen-Williams C)	CPHEEO 2024 Table 6.2 value for cement-mortar-lined DI; HDPE and PVC are 145.

The New blank metric project in File > Start / Sample Networks... sets these values for you. The ID Labels tab is read-only: new objects are numbered 1, 2, 3 and so on, skipping IDs already in use. The Hydraulics tab shows the current analysis options and links to Project > Analysis Options... to change them.

Add objects

Junction, reservoir, tank: pick Add Junction, Add Reservoir or Add Tank and click the map. The tool stays active, so you can place several in a row, and each new object is selected so you can type its properties straight away.
Pipe, pump, valve: pick Add Pipe, Add Pump or Add Valve, click the start node, then the end node. For a pipe, clicks on empty map between the two add bend points. Esc or a right-click cancels a link you have started.
Label: pick Add Label, click the map, type the text and press Enter.
From the Browser: on the Data tab choose a category and press Add; it picks the matching map tool for you.

The start node of a link matters: a positive flow runs from start to end, a pipe set to CV only lets water flow that way, and a valve acts on the side downstream of its start node.

Choose the right object

On site	Model it as	Notes
WTP clear water reservoir, large source, bulk supply point	Reservoir	A fixed water level that never runs dry. Enter its Total Head in metres above datum.
ESR, GSR, sump, balancing tank	Tank	Elevation is the tank floor; levels are measured up from it. The level rises and falls during a run.
Street tap points, a cluster of house connections	Junction	Carries the Base Demand and the Elevation of the ground.
Sluice valve	Pipe	Set Initial Status to Open or Closed.
Non-return valve (NRV)	Pipe	Set Initial Status to CV.
PRV for a low-lying zone	Valve, type PRV	Setting is the downstream pressure it holds, in metres.
Flow control valve at an ESR inlet or a village offtake	Valve, type FCV	Setting is the flow it passes, in the flow units.
Pump set	Pump	Needs a head curve or a power rating. See Pumps and pump curves.

Edit objects

Pick Select Object and click an object, or click it in the Browser list. Its properties appear in the Property Editor.
Type a new value and press Enter or click away. Esc cancels. A star marks values EPANET requires.
Drag a node with Select Object to move it. With Auto-Length on, the pipes attached to it take their new map lengths.
Patterns, curves and controls are edited from the Browser: choose the category on the Data tab and double-click an item, or press Edit.
Hazen-Williams C, per CPHEEO 2024 Table 6.2: 145 for PVC, HDPE, MDPE, GRP and PVC-O; 140 for CI, DI or MS with cement mortar or epoxy lining, and for AC; 100 for unlined CI, DI or MS; 55 for GI house connections of 50 mm and below. Old unlined pipes often perform well below the table, so calibrate against field pressures when you can.

Delete objects

Select the object and press Del, the Delete toolbar button, or Edit > Delete. Deleting a node also deletes every pipe, pump and valve connected to it, and any control that refers to it. Save a copy before deleting large parts of a network.