Disclosures

1. We are deeply dependent on EPANET

Not inspired by it, and not merely compatible with it: dependent on it. The specifics, each one listed with its source on the Citations page:

• The engine is EPANET's, and it ships inside the page. A 679 KB browser build of OWA-EPANET 2.3.5, released 2025-02-20, loaded on demand. We wrote a drawing surface and put EPANET underneath it.
• Most of the answers only exist because it is there. Extended period simulation, water age, source trace, chemical decay, pump energy, rule-based controls and pressure-reducing, pressure-sustaining and flow-control valves run through the EPANET engine and nothing else. Our own solver does one instant, pressures and flows only, and is not planned to do more.
• The interchange format is EPANET's. We read and write EPANET's own .inp file, from [TITLE] to [END] across the sections we support, and a value you did not edit comes back out character for character. We have a format of our own too: a project saves as JSON, because an .inp cannot hold scenarios, saved profile paths, the background picture itself, map tiles and your view, a Text label with more than one line, or longitude and latitude. Everything an .inp can carry still round-trips through one, and the five things it cannot are reported rather than dropped.
• We check ourselves against EPA's own published answers. Our extended period simulation is compared against EPA's own report for its Net3 example network: 2,425 head comparisons across 25 reporting steps, agreeing to 0.005 ft. Water quality is anchored on the same report, worst difference 0.105%. Pump energy is anchored on that report's own energy table. EPANET is the truth we are measured against.
• Even the arithmetic is EPANET's. Our one Hazen-Williams coefficient pair is derived from EPANET's h = 4.727 L Q^1.852 / (C^1.852 d^4.871), not from the more commonly quoted metric restatement. The two disagree by up to 0.12% from 50 mm to 2 m, and we chose to agree with EPANET, because EPANET is what our users will check us against.
• The vocabulary is EPANET's. Junction, reservoir, tank, pipe, pump, valve. Extended period simulation. Trials and iterations, static pressure, drawdown, converge. The four curve types. The grammar of a rule. What happens when you change a unit. An engineer who knows EPANET should not have to learn a second dialect from us, and a build check fails when we start writing one.
• The interface is inspired by and informed by EPANET's. Its curve editor and its table of assets are where ours came from, and its five map colours are in our palette unsoftened, though our default is Viridis. Not downstream of it: scenarios, a world map, find and replace, flexible multi-labels, a menu system we hope is easier, and being a web page rather than a Windows program. Some of that is better and some is just different.

That is the dependency graph. If EPANET had not existed, or had not been given away, this project would not exist.

2. Our license is less free than EPANET's

Not public domain; less free than EPANET; less trusting than EPANET; arguably less collegial than EPANET. For better or for worse, we are currently working under Richard M. Stallman’s GNU General Public License 3.0, which is aggressively restrictive against locking up this work. The rationale is that this protects us all against property hoarders. Talk to us about this if you see the error of our ways.

EPANET carries no license at all, because a work of the United States government has no copyright to license. Anybody may take it and do anything, including take it private. We chose a license that forbids that, which is a restriction we impose and EPA did not. Reasonable people disagree about whether that is generosity or distrust. If you think we got it wrong, write to us.

3. We are new, with all that implies

Development started on 28 July 2026. As of 1 September 2026 the software has carried one real-world design report. Counting the defects found and fixed since would tell you nothing you could use; what those two dates tell you is that the ones nobody has hit yet are still in there.

One claim about ourselves a future surprise cannot falsify:

We are what we are, and it’s good and useful and usable. But we have no idea what we are not and what we don’t know.

We do not publish a completeness claim against EPANET. EPANET has depth we keep discovering by accident.

4. This is AI-assisted, and here is the reason

The software and this website are written with heavy use of AI. Tom Haws asked that his own statement of why be carried as he wrote it:

This would not be possible without AI. Tom Haws decided in 2026 that if AI is going to destroy the world, he better not use it for cat videos. His only justification for using AI is to tell the world the highest message of heaven: That they are loved and cherished forever, that they have nothing to fear, and that they are not ruining everything.

5. Nobody has vetted this on your behalf

No EPA affiliation, no government affiliation, no university affiliation, no sponsor, no foundation, and no funding. Nobody has vetted this software on your behalf. Every claim on this page is one you can check yourself: they are set out one by one, each with its source, on the Citations page.