Free EPANET Alternatives (2026): Browser & Desktop
EPANET has been the default free tool for pipe network analysis for decades. It's reliable, maintained by the US EPA, and its .inp file format is a de facto standard. But it was built for one job — water-distribution modelling on Windows — so if you need a modern interface, cross-platform access, or compressible (gas) flow, you'll quickly hit its limits.
This guide compares the realistic EPANET alternatives in 2026 — both free and commercial — and where each one genuinely fits.
What EPANET does well — and where it stops
EPANET is excellent at what it was designed for: steady-state and extended-period simulation of water-distribution networks — pressures, flows, tank levels, and water quality across large municipal systems. It's free, open source, and battle-tested.
Its limits are just as clear:
- Windows desktop — officially distributed as a Windows app, with no native browser, macOS, or Linux build (cross-platform access relies on community ports).
- Incompressible water only — no compressible gas or steam flow, so it can't model pneumatic, natural-gas, or steam lines.
- Dated interface — the UI has a steep learning curve and hasn't changed much in years.
- No built-in component sizing — valve sizing (IEC 60534), orifice plates (ISO 5167), and fitting losses aren't part of the workflow.
If those gaps matter to you, here are the alternatives worth knowing.
Comparison at a glance
| Tool | Type | Platform | Flow | Pricing | Best for |
|---|---|---|---|---|---|
| EPANET | Open source | Windows desktop | Water (incompressible) | Free | Water-distribution utilities |
| SimuPipe | Freemium | Browser (any OS) | Liquid + compressible gas | Free / €39 mo | Modern, no-install, gas + liquid, .inp import |
| AFT Fathom | Commercial | Windows desktop | Liquid (incompressible) | Paid licence | In-depth liquid systems |
| AFT Arrow | Commercial | Windows desktop | Compressible gas | Paid licence | Rigorous gas systems |
| Pipe-Flo | Commercial | Windows desktop | Liquid | Paid licence | Plant liquid piping |
| PIPESIM | Commercial | Windows desktop | Multiphase | Paid licence | Oil & gas / multiphase |
| Bentley WaterGEMS | Commercial | Windows / CAD | Water (incompressible) | Paid licence | Large water utilities |
EPANET (the baseline)
Still the right choice for large water-distribution utilities — water-quality modelling, extended-period simulation, and 10,000-node city networks are where it shines, and it's free. If you model municipal water and live on Windows, EPANET (or a commercial tool built on its engine) is hard to beat.
SimuPipe — free, browser-based, liquid + gas
SimuPipe runs entirely in the browser — no install, any OS — with a visual drag-and-drop editor. It covers what EPANET doesn't: compressible gas flow (isothermal and adiabatic solvers) alongside incompressible liquid, plus IEC 60534 valve sizing, ISO 5167 orifice plates, and Crane TP-410 fittings built into the workflow. It imports EPANET .inp files, so you can bring existing models across, and there's a genuinely usable free tier (Pro is €39/mo).
Honest scope: SimuPipe isn't trying to replace EPANET or WaterGEMS for city-scale water-quality and extended-period utility modelling. It's the better fit when you want a modern, no-install tool for liquid and compressible-gas piping — process, plant, HVAC, pneumatic, and gas systems — without desktop lock-in or a four-figure licence.
AFT Fathom & AFT Arrow
AFT's tools are a commercial standard for rigorous system modelling. Fathom handles incompressible liquid systems with full energy balance; Arrow handles compressible gas. Both are powerful, well-validated, and widely used in industry — but they're Windows-desktop, commercial per-seat licences, with a corresponding learning curve. Choose them when you need their depth and have the budget.
Pipe-Flo
A long-standing commercial desktop tool for liquid piping systems, strong on documentation and "calculated-by-design" workflows for plant piping. Windows-only, commercial licence — a solid choice for liquid-system design teams already in that ecosystem.
PIPESIM
A specialised, commercial multiphase flow simulator (SLB) for oil & gas production and pipeline systems. If your problem is multiphase (oil/gas/water) production modelling, PIPESIM is in a different category from the single-phase tools above — powerful and priced accordingly, but overkill for ordinary single-phase liquid or gas piping.
Bentley OpenFlows / WaterGEMS
Commercial water-distribution modelling built on the EPANET engine, with CAD/GIS integration for utilities. If you need EPANET-grade water modelling plus enterprise features and support, this is the upgrade path — at enterprise pricing.
How to choose
- Municipal water distribution (large, water quality): EPANET (free) or Bentley WaterGEMS (commercial).
- Compressible / gas piping, rigorous and commercial: AFT Arrow.
- In-depth liquid systems, commercial: AFT Fathom or Pipe-Flo.
- Multiphase oil & gas: PIPESIM.
- Free, browser-based, liquid + gas, no install,
.inpimport: SimuPipe.
If your main reasons for leaving EPANET are "I want a modern interface, cross-platform access, and compressible-gas support without a desktop install or a big licence" — that's exactly what SimuPipe is built for. Start with the free friction loss and valve sizing calculators, browse the engineering reference tables, or open the editor and import your EPANET .inp file.