EPANET Total Head Explorer

Elevation + Pressure = Total Head

EPANET reports hydraulic head at every node — the water's total mechanical energy, expressed as a height. It always splits into two pieces you set separately in a model.

Elevation, E 700 ft

Pressure head, P 130 ft

Result

Total head, H = E + P—

Pressure (psi) = P ÷ 2.31—

The dashed teal line is the hydraulic grade line — how high water would rise in a thin open tube stuck into the pipe there. Its height above the node is pressure head; its height above datum is total head.

Reservoir → J1 → J2

Head is lost to friction moving down each pipe. EPANET walks the energy equation h_i − h_j = headloss across every link in turn.

Reservoir

Head, H_R

Pipe 1

Length

Diameter

C-factor

Junction 1

Elevation

Demand

Pipe 2

Length

Diameter

C-factor

Junction 2

Elevation

Demand

Node-by-node results

Flow in Pipe 1 (J1+J2 demand)—

Headloss, Pipe 1 (Hazen-Williams)—

Head at J1—

Pressure at J1—

Flow in Pipe 2 (J2 demand)—

Headloss, Pipe 2—

Head at J2—

Pressure at J2—

Why looped networks need iteration

A straight chain solves node-by-node, like Tab 2. The moment a junction is reachable two ways — like the parallel pipes below — the flow split is unknown until heads and flows are solved together. EPANET's Global Gradient Algorithm (Todini & Pilati, 1988) guesses flows, linearizes the headloss-vs-flow relation, solves for nodal head, corrects the flows, and repeats until the imbalance is negligible. Below is that same logic worked by hand on the smallest network that needs it.

Network

Reservoir head, H_R

Demand at J

Elevation at J

Pipe A

Length

Diameter

C-factor

Pipe B

Length

Diameter

C-factor

Iteration log

Iter	h_J (ft)	q_A (gpm)	q_B (gpm)	Δflow/flow

Balance check at convergence

q_A + q_B vs demand D—

H_R − h_J vs headloss A—

H_R − h_J vs headloss B—

Pressure at J—

Headloss formulas EPANET can use

All three reduce to h_L = A · q^B (headloss in ft, flow in cfs). EPANET fits A from a pipe's length, diameter and roughness, and re-derives it whenever those change.

Formula	Resistance coeff. A	Exponent B	Roughness input
Hazen-Williams	4.727·C⁻¹·⁸⁵²·d⁻⁴·⁸⁷¹·L	1.852	C-factor
Darcy-Weisbach	0.0252·f(ε,d,q)·d⁻⁵·L	2	ε, roughness (ft)
Chezy-Manning	4.66·n²·d⁻⁵·³³·L	2	Manning's n

Handy constants

Pressure ↔ head (water, SG = 1)1 psi ≈ 2.31 ft

Reynolds regimes (Darcy-Weisbach)laminar <2,000 · turbulent >4,000

Default GGA convergenceΣ|Δq| / Σ|q| < 0.001

Reference: Todini & Pilati (1988); EPANET 2.2 User Manual, US EPA (2020).