Solves one set of demands at a time, using the same global gradient algorithm EPANET uses. It does not model how the network changes over time.
Not modeled
Tanks, water quality, and control valves that open and close on their own (PRV, PSV, FCV) are not modeled. A pipe can carry a fixed minor loss, but not a valve whose open or closed state depends on the flow being solved for.
Saving projects
Every project is a tab, and every tab is saved in this browser as you work. Clearing your browser data deletes them all, so keep your work in a file: File, Save as. An asterisk on a tab means it holds changes that are not in a file. Nothing is ever written to a file unless you ask. In some browsers a project connects to the file you save it to, and File, Save writes back to that same file from then on; in others no connection is possible, so Save is disabled and only Save as is available. When a project file is kept on a shared drive, this page tells you if a colleague already has it open, so that two people do not write over each other.
Pump curve
A pump follows H = H₀ − aQ^b, where H is the head the pump adds and Q is the flow through it. Enter one, two, or three points from the manufacturer's curve. Three points — the head at zero flow, the normal working point, and the point of highest flow — fit H₀, a and b directly, and follow a published curve most closely. Two points fit a parabola (b = 2) with its peak at zero flow. One point uses a common rule: the head at zero flow is 1.33 × the head you enter, and the highest flow is 2 × the flow you enter, which again gives b = 2. A pump with no points entered adds no head at all. The curve is not cut off where the head reaches zero, so asking a pump for more flow than its curve can deliver gives a negative head. The fix is a bigger pump or a smaller demand, not a different curve fit.
Planned additions
Scenarios, so that one project can hold several sets of demands. Tables of node and pipe results. Opening a file you used recently without hunting for it again. Reading and writing EPANET .inp files. Comments and suggestions are always welcome (see the feedback link above).
Hazen-Williams constants match EPANET
In August 2026 the Hazen-Williams coefficient and exponent were changed to match EPANET. Head loss results differ from earlier versions of this page by up to 0.1 percent, which is far smaller than the uncertainty in the C value itself.