EPANET alternatives: the pipe-network tools, compared

EPANET is the US EPA's free, public-domain water-distribution modeller. It solves steady-state and extended-period hydraulics, tracks water quality and age, and has been the reference implementation for pipe-network analysis for three decades. If you are reading a page about alternatives to it, you have almost certainly hit one of its edges rather than a fault: it is a Windows desktop program, it models water, and its interface was built for municipal distribution modelling rather than for the plant, process or building-services network on your desk this afternoon.

This guide covers the tools engineers actually move to, what each is genuinely for, and where each one stops. It is written by the people who build one of them, Fluid Network Studio, so read our own entry with that in mind. Every claim about another product is drawn from that vendor's own public material, and pricing moves, so check the vendor before you buy anything.

First, decide what you are actually short of

Most "EPANET alternative" searches come down to one of five gaps. Naming yours narrows the field fast.

Access. You need it on macOS or Linux, on a locked-down work machine, or on site from a tablet. This rules out most of the field, which is Windows desktop software.

Fluids other than water. Compressed air, process gas, a hot or cold line where temperature changes along the run, a sludge or a polymer solution. EPANET models incompressible water only, and this is the single most common reason people leave it.

Time behaviour. Tanks filling and draining, pumps cycling on level, valves on a schedule. EPANET does this well, so if it is all you need, the honest answer is to stay.

Fast transients. Water hammer, surge, a pump trip, a valve slam. Neither EPANET nor any quasi-steady tool models fluid inertia. You need a dedicated surge package, and no amount of extended-period simulation substitutes for one. The glossary explains why, and gives the Joukowsky screening estimate.

Proof you can hand to someone. A report that names its methods, states its assumptions and shows the results were checked against something independent.

The tools

EPANET itself

Free, public domain, and still the right answer for a large class of work: municipal water distribution, water-quality and age tracking, chlorine decay, and long extended-period runs on big models. It is a Windows program, it models incompressible water, and it does not do gas, heat transfer or non-Newtonian fluids. Its solver is the Global Gradient Algorithm of Todini and Pilati, which is also what most of the field, including us, uses. If your only complaint is the interface, look at the EPANET-based front ends before you leave the ecosystem entirely. The EPA distributes it at epa.gov/water-research/epanet, and the community-maintained build most tools cross-check against is OWA-EPANET.

epanet-js

The closest thing to EPANET itself in a browser, and the nearest neighbour to us on this list, so it deserves a straight answer. epanet-js is a web application built around a full WebAssembly port of the OWA-EPANET toolkit, which means the numbers come from the actual EPANET engine rather than a reimplementation of it. If your priority is that a model behaves exactly as EPANET behaves, its compatibility is genuinely stronger than ours: it is the same solver, water quality and all. It reads and writes .inp files, runs steady-state and extended-period simulation, and does the water-quality, age and trace analysis that we do not attempt. The source is public: the original code is MIT-licensed, and later work is under FSL-1.1-MIT, a Functional Source License that converts to MIT after two years. The repository is at github.com/epanet-js/epanet-js.

It is free to use at the base tier, with paid Pro and Teams tiers (listed at $950 a year and $4,400 a year plus a per-user fee at the time of writing) that add scenario comparison, a richer model builder and supported use. Check the vendor for current terms.

Where it stops is scope of physics. epanet-js models incompressible water, because EPANET models incompressible water. It does not do compressible gas, heat transfer through pipe walls and insulation, or non-Newtonian fluids, and that is the honest difference between it and us rather than anything about interface or price. If your work is water distribution and you want EPANET fidelity without the Windows install, look at epanet-js first. If your work includes compressed air, a line whose temperature changes along the run, or a sludge, that is where we come in.

Fluid Network Studio

Ours. A browser-based network solver: draw the network in a tab, press solve, read flows, pressures, velocities and temperatures. It covers incompressible liquids, compressible gas, liquids and gases with heat transfer through pipe walls and insulation, and homogeneous non-Newtonian fluids (power-law and Bingham plastic). Extended-period simulation, with tanks, valve schedules and pump control, is included on every plan rather than sold as a module. Water and liquid networks are free with no account needed to solve, and gas, heat, non-Newtonian flow and the CFD-coupling export are on Advanced at A$39 a month.

It reads and writes EPANET .inp files, so an existing model comes across rather than being retyped. Methods are named openly - Global Gradient Algorithm, Darcy-Weisbach with the Churchill friction factor, fixed-K minor losses using coefficients of the class published in Crane TP-410, least-squares pump curves with affinity scaling - and results are checked against a published reference problem set that includes independent cross-checks against OWA-EPANET 2.2 and NASA's GFSSP, with mass and energy conservation residuals reported on every solve. That set covers the methods, not the tabulated numbers: the fitting K values and material roughnesses are sourced prefills you can edit, and we say so on how it works rather than let "verified" cover the whole tool.

What it will not do: water hammer, surge or any fast transient, because its time simulation is quasi-steady and carries no fluid inertia. It does not model settling or heterogeneous slurries. It does not track water quality, age or tracers. It does not size relief valves to a code. Those are boundaries, not roadmap items.

Pipe Flow Expert

Windows desktop software with openly published annual licences, from a small Lite edition up to full and multi-user versions, with lower renewal fees after the first year. In spirit it is the closest desktop tool to what a practising engineer wants day to day: focused network sizing, no municipal-modelling scaffolding. If you want desktop software with a price on the website and no sales call, start here. Vendor site: pipeflow.com.

AFT Fathom

A deep incompressible pipe-flow suite from Applied Flow Technology, now part of Datacor, widely used in process and power engineering, and now listed on the Datacor product site. Pricing is by quote through the vendor and its resellers. Its stablemates cover compressible flow and surge, so the family spans more than Fathom alone does. It is a serious engineering package with a learning curve and a licence to match, and it is a sound choice when pipe-flow analysis is a large part of the job rather than an occasional task.

PIPENET

From Sunrise Systems, the specialist for oil and gas, power and process plants. Its Transient module does surge and water hammer properly, and its Spray/Sprinkler module targets NFPA fire-protection design. Pricing is discussed with the vendor. If your problem is a surge study or a code-compliant fire system, this class of tool is where that work belongs, and nothing in the browser-based category replaces it.

PipelineStudio

Emerson's tool for long-distance gas and liquid transmission pipelines, covering steady-state and transient analysis, priced by quote. This is transmission engineering rather than facility or utility networks. If you are sizing a plant, a compressed-air ring main or a pumped liquid network, it is more tool than the job needs. If you are running a transmission line with transients, it is the right one.

Bentley OpenFlows WaterCAD and WaterGEMS

The municipal water-distribution standard, sold as annual practitioner licences through Bentley's Virtuosity store with pricing tiered by pipe count. WaterGEMS adds GIS and CAD integration and model-management tooling on top of WaterCAD, and Bentley now presents the family as OpenFlows Water. For thousands of nodes, water-quality tracking, fire-flow studies and a model that lives for years, this is the category EPANET users step up into.

Which one for which job

If you are leaving EPANET, what comes with you

An .inp file is the closest thing this field has to an interchange format, and it travels better than people expect. Importing one into Fluid Network Studio brings across the junctions, reservoirs, tanks, pipes, pumps and valves, their geometry and coordinates, and the unit system the file was written in. Control valves keep their control law rather than degrading to plain throttles.

What does not come across, and we would rather say so before you try it. [QUALITY] and [REACTIONS] are dropped, because water-quality modelling is out of scope here. Demand patterns, controls and rules are not evaluated on import, so a patterned model arrives as a steady one. Pressure-dependent emitters are not carried across either. The import reports every element it skipped and why, so you get a list rather than a silent difference. Export runs the other way too, so a network built here can go back to EPANET for a water-quality run.

Drafting a model with an AI assistant

You can describe a network to an AI assistant and import what it writes. Fluid Network Studio publishes a guide for assistants, you give it to the one you already use, and the reply comes back as a file the Studio checks: every unit, every connection and every library name, with the assistant's own assumptions listed before anything loads. Liquid networks solve free in the browser, and a draft built this way exports to EPANET .inp on the Advanced plan like any other network. It is a way to get a first model on screen in a few minutes. The checking is structural, so the engineering judgement is still yours.

Frequently asked questions

What is the best free alternative to EPANET?

There are two honest answers, and which one is best depends on what you are short of. If you want EPANET's own results in a browser, including water quality and age, epanet-js has a free tier and runs the EPANET engine itself. If you want water networks solved free with no account at all, and the option of gas, heat transfer or non-Newtonian fluids later, Fluid Network Studio is free for liquids and cross-checks its incompressible results against OWA-EPANET 2.2. Most engineers who leave EPANET for us do so because they need physics EPANET does not model, or because they are not on Windows.

Is there an EPANET alternative that runs in the browser?

Yes, and there is now more than one. Fluid Network Studio runs in any modern browser on any operating system, with nothing to install and no licence server, which also means it works on a locked-down work machine and on a tablet on site. epanet-js does the same for water distribution specifically, by running the EPANET engine compiled to WebAssembly. Between them the browser is a real option for this work, which it was not a few years ago.

Can I open my EPANET .inp file in something else?

Yes. Fluid Network Studio imports EPANET .inp files, keeping the network, its geometry and its control-valve behaviour, and exports back to .inp. Water-quality sections, demand patterns and rule-based controls are not carried across, and the import lists exactly what it skipped.

Does any EPANET alternative handle gas or heat transfer?

EPANET models incompressible water only. Fluid Network Studio solves compressible gas in absolute pressure with mass-flow balances, and models heat loss or gain through pipe walls and insulation with named film correlations. In the desktop category, the AFT family and PIPENET both cover compressible flow, and PipelineStudio covers gas transmission.

What can EPANET do that a browser tool cannot?

Very large municipal models that live for years and are managed as an asset, with the surrounding GIS and asset tooling that goes with them. Water quality, age and tracer tracking used to belong on this list too, and Fluid Network Studio still does not attempt them, but epanet-js now carries them into the browser by running the EPANET engine itself. The dividing line between these tools is scope of physics and scale, not where the code runs.

Which alternatives model water hammer?

Of the tools here, PIPENET Transient and PipelineStudio do transient analysis, and dedicated surge packages exist for exactly this. Neither EPANET, epanet-js nor Fluid Network Studio models fluid inertia, so none of them can size a surge vessel or predict a valve-slam pressure. Extended-period simulation is not the same thing, and no tool should let you believe it is. Our glossary sets out why a quasi-steady solver cannot produce a pressure wave, and gives the Joukowsky estimate that tells you in one line whether the problem is worth a surge study.

How to choose without wasting a fortnight

Take a network you already know the answer to - one you have hand-calculated, or one from a textbook, or an existing model you trust - and build it in whatever you are evaluating. If the tool cannot reproduce a result you already trust, nothing else about it matters. If it can, then judge it on the things you will live with daily: how long it takes to get from a question to an answer, whether it tells you what it did, and whether the output is something you would put your name on.

That last part is why our verification cases are public and solved live rather than quoted from a document. See how it works for the methods end to end, the verification cases for the numbers, and the full comparison against desktop packages for where each one wins.

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