INP Format Support

Hydra parses the EPANET 2.3 .inp file format. This page documents which sections and keywords are supported, which are silently ignored, and where Hydra’s behaviour differs from or extends the standard.

Sections

Fully Supported

All data in these sections is parsed and applied.

Section	Contents
`[TITLE]`	Up to 3 title lines (preserved verbatim)
`[JUNCTIONS]`	ID, elevation, base demand, demand pattern
`[RESERVOIRS]`	ID, head, head pattern
`[TANKS]`	ID, elevation, initial/min/max level, diameter, minimum volume, volume curve, overflow flag
`[PIPES]`	ID, nodes, length, diameter, roughness, minor loss, status
`[PUMPS]`	ID, nodes, keyword parameters (HEAD, POWER, SPEED, PATTERN)
`[VALVES]`	ID, nodes, diameter, type (PRV, PSV, FCV, TCV, GPV, PBV, PCV), setting, minor loss
`[DEMANDS]`	Additional demand categories per junction
`[EMITTERS]`	Per-junction emitter coefficient
`[STATUS]`	Initial link open/closed status overrides and numeric setting overrides (pump speed, valve setting)
`[PATTERNS]`	Multiplier sequences (multi-line continuation supported)
`[CURVES]`	XY data points for pump head, pump efficiency, GPV headloss, PCV loss ratio, tank volume
`[CONTROLS]`	Simple time-based, level-based, and pressure-based controls
`[RULES]`	Rule-based controls with IF/AND/OR/THEN/ELSE/PRIORITY
`[QUALITY]`	Per-node initial quality concentrations
`[SOURCES]`	Quality source injection (CONCEN, MASS, FLOWPACED, SETPOINT)
`[MIXING]`	Per-tank mixing model (MIXED, 2COMP, FIFO, LIFO)
`[REACTIONS]`	Global and per-element bulk/wall reaction coefficients and orders
`[ENERGY]`	Global price/efficiency and per-pump energy settings (EFFIC, PRICE, PRICEPATTERN)
`[TIMES]`	Simulation duration, timesteps, report start, pattern start, clock offset
`[OPTIONS]`	See OPTIONS keywords below
`[REPORT]`	Report field selection and formatting options
`[COORDINATES]`	Node XY positions (visual metadata, no unit conversion)
`[VERTICES]`	Link intermediate vertices (visual metadata)
`[TAGS]`	Node and link string tags (metadata)
`[LEAKAGE]`	Per-pipe FAVAD leakage coefficients, added in OWA-EPANET 2.3; not present in legacy EPANET 2.2

Silently Ignored

These sections are recognised and accepted without error but produce no simulation effect. Files containing them parse cleanly.

Section	Notes
`[ROUGHNESS]`	Legacy EPANET 1.x section, superseded by roughness column in `[PIPES]`
`[LABELS]`	Map label annotations (visual only)
`[BACKDROP]`	Background image metadata (visual only)

Unknown sections (not listed in either table) are also silently ignored for forward compatibility.

OPTIONS Keywords

All standard EPANET 2.3 [OPTIONS] keywords are supported. Unknown keywords are silently ignored.

Keyword	Description
`UNITS`	Flow unit system (CFS, GPM, MGD, IMGD, AFD, LPS, LPM, MLD, CMH, CMD, CMS)
`HEADLOSS`	Head-loss formula (H-W, D-W, C-M)
`VISCOSITY`	Kinematic viscosity relative to water at 20 °C
`DIFFUSIVITY`	Molecular diffusivity relative to chlorine at 20 °C
`SPECIFIC GRAVITY`	Specific gravity relative to water at 4 °C
`TRIALS`	Maximum Newton-Raphson iterations
`ACCURACY`	Relative flow convergence tolerance
`UNBALANCED`	Behaviour on non-convergence (STOP or CONTINUE N)
`PATTERN`	Default demand pattern ID
`DEMAND MULTIPLIER`	Global demand scale factor
`DEMAND MODEL`	DDA or PDA
`MINIMUM PRESSURE`	PDA: pressure below which demand = 0
`REQUIRED PRESSURE`	PDA: pressure at which full demand is delivered
`PRESSURE EXPONENT`	PDA: pressure-demand exponent
`EMITTER EXPONENT`	Global emitter discharge exponent
`QUALITY`	Quality mode and constituent name/units
`TOLERANCE`	Quality segment merge tolerance
`CHECKFREQ`	Status-check interval (iterations)
`MAXCHECK`	Iteration limit for status checks
`DAMPLIMIT`	Flow accuracy threshold for damping activation
`FLOWCHANGE`	Maximum per-iteration flow change limit
`HEADERROR`	Per-link head balance error limit
`HTOL`	Head tolerance for link status transitions
`QTOL`	Flow change tolerance for link status transitions
`RQTOL`	Minimum gradient clamp for emitter/pump linearisation
`BACKFLOW ALLOWED`	Whether emitters may admit reverse flow (YES/NO)

Pump Curves

A single-point pump curve (Q₁, H₁) is automatically expanded to a three-point power-function curve (0, 1.33334·H₁), (Q₁, H₁), (2·Q₁, 0), matching EPANET’s internal behaviour.

LEAKAGE Section

[LEAKAGE] was added in OWA-EPANET 2.3 and is not present in legacy EPANET 2.2 files. Each row specifies per-pipe FAVAD (Fixed and Variable Area Discharge) leakage coefficients:

[LEAKAGE]
;PipeID   C1       C2
P1        0.0002   0.5
P2        0.00015  0.6

Where C1 is the fixed-area discharge coefficient and C2 is the variable-area discharge coefficient. Standard EPANET files (without a [LEAKAGE] section) parse cleanly; leakage is simply zero for all pipes.

Differences from EPANET 2.3

Area	EPANET 2.3 behaviour	Hydra behaviour
Quality timestep minimum	Can become 0 s (integer division truncation) when hydraulic step is very small	Enforced minimum of 1 s to prevent zero-length sub-steps
`UNBALANCED STOP`	Halts the EPS on the first step that does not converge within `TRIALS` iterations	Halts with a warning and returns a partial result; simulation terminates at that step
GGA numerical path	Specific convergence trajectory tied to EPANET’s C implementation	Independent GGA path: per-step hydraulic solutions are close but not byte-identical; differences can cascade into larger deviations over long quality runs or in networks with many demand periods

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