EPANET++ is a free web application for modeling water distribution networks, an extension of EPANET.

Demand scaling

Press the Run button to multiply the demands at the chosen junctions by the demand scale and see the pressures and velocities.

Press the Find button to find the largest demand scale, to the nearest 0.01, at which all these junctions keep at least the lowest pressure allowed; it searches from 0 to 20.

Both work on a copy of the network, solved at the time step on screen in the active scenario, so nothing in your project is changed. By default only the time step on screen is scaled, and levels and statuses are taken from it. When the project has an extended-period simulation, set Reporting step tested to The whole run to scale the demands over the entire run: every reporting step is judged, a tank that empties fails the scale, and the answer names the limiting reporting step.

Run

Run multiplies the demands at the chosen junctions by the Demand scale, on a copy of the network at the time step on screen and in the open scenario. It makes two solves, one with the demands as they are and one scaled. The result lists the Lowest pressures and the Highest velocities, each with the Scaled value beside the Unscaled one, which is the value the map shows. Each list holds ten rows, and the box states how many links it does not show. The Demand scale is applied in addition to the demand multiplier of the open scenario, and it is never saved in the project.

Find

Find searches demand scales from 0 to 20, to the nearest 0.01, for the largest one at which every chosen junction keeps at least the Lowest pressure allowed. It reports the scale and the lowest pressure there, and the same for the next step up, where the pressure first falls below the limit. If the demands as entered already leave a junction below the limit, the answer is marked with a warning sign. If every junction keeps the limit at 20, the answer says so. Stop ends a search without an answer. Lowest pressure allowed is the same setting as the Lowest system pressure allowed box of the Fire flow analysis.

Junctions, and the time step

With Selected junctions, only the junctions selected on the map are scaled and checked. Other junctions are left as they are, and those that fall below the limit are listed without limiting the answer. Only the time step on screen is scaled, and levels and statuses are taken from it. To test the peak, move the clock to the peak demand before running.

Example on Net1

Open the Net1 example and choose Water, Analyze, Demand scaling…. At the time step 0:00, click Find with the box as it opens. Every junction keeps at least 20 psi up to a demand scale of 5.76, where the lowest pressure is 20.11 psi at junction N32. At 5.77 it is 19.8 psi, and the search took 13 solves. Enter 3 for Demand scale and click Run: Junction N32 falls from 111 psi, unscaled, to 85.99 psi, and Link L112 rises from 0.535 ft/sec to 3.13 ft/sec.