EPANET Bug for Variable Speed Pumps

Dear EPANET Users,

Charles Schumate of LAN Engrs. discovered a bug in the way that EPANET adjusts pump curves for relative speed factors other than 1.0. The resulting adjusted pump curves will not obey the laws of hydraulic similarity, depending on how far from 2.0 the exponent in the original pump curve is. (For generic pump curves, where you supply only a single point on the curve, the exponent is always 2.0 so there will be no error.)

I've decided to implement the fix-up in Version 2 rather than release another minor version right away (it will give me more incentive to finish Version 2 sooner). So for now, I suggest not using the variable pump speed feature unless your pump curve exponents are close to 2.0.

(Charles gets a lifetime supply of free EPANET upgrades for discovering this problem).

Lew Rossman