GeoPilotDrainPilot DocumentationOpen DrainPilot

Getting started

Open a sample storm drain model, run it on the EPA SWMM 5.2.4 engine, read the results and save your work, in about five minutes.

DrainPilot is a storm water and sewer modelling workspace that runs in your browser. It solves models with EPA SWMM 5.2.4 compiled to WebAssembly, the same engine as the desktop EPA SWMM program, and reads and writes standard SWMM .inp files. Nothing needs to be installed, and your files are not uploaded: the engine runs on your computer.

When DrainPilot opens it loads EPA SWMM Example 1, a small combined network in US units (CFS). The name of the open file is shown in the bar at the top, next to the project title.

Open a sample

Choose File > Start / Examples.... The Start window offers two ways to begin from nothing, and ten ready-made models:

The Start / Examples window. At the top, New project (SI) and Import a survey... buttons. Below, DrainPilot samples with Indian norms: Indian sewer zone (a separate sewer zone designed to CPHEEO norms with a pumping station) and Indian storm catchment (an urban catchment with a 5-year design storm and open drains). Then the EPA SWMM examples, Example1 to Example5, the metric and dynamic wave copies of Example 1, and Inlet-drains, each with a one-line description and its source.
The Start window. Click a card to open a sample, or New project (SI) for an empty metric model.
  • New project (SI) starts an empty project in litres per second. See Building a network.
  • Import a survey... builds a project from a manhole and pipe schedule, a DXF drawing or GIS layers. See Import and export.
  • DrainPilot samples (Indian norms): Indian sewer zone, a separate sewer zone with dry weather flow and a pumping station, and Indian storm catchment, an urban catchment on a 5-year design storm draining through open drains. Both are synthetic, not real towns, and both are in LPS with dynamic wave routing.
  • EPA SWMM examples: eight public domain models from EPA, including Example 1 in US and SI units, rule-based pump controls (Example3) and LID controls (Example4).

Click a card to open it. The same models are on the File > Open DrainPilot Sample and File > Open Example submenus.

  1. Choose File > Start / Examples...
  2. Click Indian storm catchment. The map shows 13 subcatchments, 13 junctions, the drains joining them and one outfall.

Run the simulation

Click Run on the toolbar, press F5, or choose Project > Run Simulation. The Run Status box shows Running SWMM... with a progress bar and the percentage done, and a Cancel button. When the run ends it reports one of:

The Run Status box reading Run was successful. (1.2 s) with an OK button.
A successful run. Press OK to read the results.
  • Run was successful. with the time the run took. Press OK.
  • Run was successful, with warning messages. See the Status Report. The results exist but need checking. Press Status Report, or see Fixing problems.
  • Run was unsuccessful. followed by SWMM's reason. The Status Report opens by itself.
  • Run was not started. The model reads a rain or other data file that is not attached yet. See Running a simulation.

Read the results

The study area map of the Indian storm catchment after a run: square subcatchments SA1 to SA3, SB1 to SB3 and SJ1 to SJ7 around a cross-shaped drain network ending at an outfall triangle on the right. Drains are coloured by flow and junctions by depth, with the Node Depth and Link Flow legends at the bottom left and the time 2026-01-01 01:15 (day 0) beside them.
The map after a run, coloured by node depth and link flow at the time shown.
  • After the first run of a model whose map is not coloured yet, DrainPilot colours nodes by Depth and links by Flow. The legend boxes at the bottom left of the map show what each colour means, with the reporting period beside them.
  • Click a junction or a drain to see its properties in the Property Editor on the right. Results for the current reporting period are in the grey rows under RESULTS at the bottom.
  • The Map tab of the Project Browser chooses what the map is coloured by and which reporting period it shows, and plays the run as an animation.
  • For graphs, the profile plot, the animation window and map queries, see Viewing results.
  • To check the drains against the CPHEEO storm water manual, use Design > Storm Compliance (SWM)..., described in Storm drain compliance.

The status bar at the bottom shows Results current after a good run. As soon as you edit anything it changes to Results out of date; run again to bring the results up to date.

Save your work

File > Save (Ctrl+S) downloads the project as an .inp file, named after the open file. File > Open... (Ctrl+O) opens an .inp file from DrainPilot, from EPA SWMM or from any program that writes the SWMM 5 format. The file you download is your copy of the model, so save often.

DrainPilot also keeps one autosave of the open project in this browser, written a moment after each edit. If the tab closes by accident, File > Restore Autosave reopens it. It is a safety net, not a substitute for saving: it holds one project only, and clearing the browser's site data removes it.

Where next

Next: The workspace