Leave Upstream ID blank and a line follows the one above it; a plain series pipeline. Enter an upstream line's ID to branch off it. So: series by default, a tree when you need it.
Branched networks only, no loops
Every line has exactly one upstream line (a tree). This tool does not solve looped networks; those need iterative methods (EPANET or similar). Leaving loops out is what keeps it simple and exact.
No active pressure controls
You can add a fixed minor-loss valve (a k-value), but not pressure-reducing or pressure-sustaining valves (PRV/PSV). Their open/closed state depends on flow and pressure, which would force iteration.
Hazen-Williams constants now match EPANET (August 2026)
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.