Drainage design, simulation and compliance
Draw the foul and surface water network over your site plan, put in the SuDS, let it size and grade every pipe, then simulate every FEH storm in EPA SWMM and see what passes and what fails against Sewers for Adoption, the Welsh SuDS standards or Sewers for Scotland. Permeable paving to ponds, water quality, coupled 1D-2D flooding, drawing sets, LandXML and IFC - at a fraction of the price of the big packages.
Manholes, gullies, rodding eyes, outfalls, tanks and pumping stations, foul and surface water in one project, over a PDF, image or DXF site plan - or open SWMM, LandXML and CSV files.
Every pipe sized and graded by Colebrook-White and the Modified Rational Method: soffits matched, cover by land use, self-cleansing gradients, and clash checks against existing services.
Permeable paving, rain gardens, bioretention, green roofs, swales, filter strips, ponds, wetlands, basins and soakaways, with vortex controls, orifices, weirs, penstocks and flap valves.
The Simple Index Approach for every catchment's SuDS train, interception of the first 5 mm, runoff volume and long-term storage, and half-emptying times.
Long sections with hydraulic and energy grade lines, a 3D view of the network, SuDS and buildings, and quantities with earthworks, your own rates and OH&P.
Import your FEH22 or FEH13 file, type the FEH99 constants, paste a depth table or add a recorded storm. Summer and winter storms with climate change and urban creep.
Sewers for Adoption (DCG v2.3), Welsh SuDS standards, Sewers for Scotland v4, Part H and BS EN 752, with clause references, one-click fixes and values you can change.
Duty and standby pumps, rising main velocity and emergency storage checks, and BRE 365 soakaway design.
Windows 10/11 · Free to design · Runs on your PC · No account
The Meadow Rise sample: 24 homes with permeable paving, a rain garden, filter strips and an infiltration basin, checked against the Welsh statutory SuDS standards.
Long sections with grade lines
Welsh SuDS and adoption checks, with fixes
Water quality by the Simple Index Approach
Drawing sets with a title block (Pro)
Designing and checking stay free. Drainage Design Pro is a subscription inside the app for engineers who need the storms simulated and the paperwork done, bought through the Microsoft Store: £29.99 a month or £249.99 a year, first week free.
Every storm, summer and winter, through the EPA SWMM 5.2 engine on your PC: surcharge, flooding, storage, pumps, hydrographs and storage-duration curves.
Sizes the storage to your discharge limit and upsizes pipes until nothing floods at 1 in 30 or surcharges at 1 in 2.
Water out of the manholes spreads over LIDAR terrain and drains back in, with buildings, direct rainfall, depth, velocity and FD2320 hazard maps, an animation and flow paths.
Drawing sets on A0 to A3 (layout, long sections, manhole and pipe schedules in adoption format, title block) and a calculation pack, ready to print to PDF.
LandXML for Civil 3D, IFC4, Excel with live formulas, DXF and SWMM .inp, and no pipe limit (the free version draws 20).
Monthly at £29.99 or yearly at £249.99 through the Microsoft Store, first week free, cancel any time.
| FEATURE | FREE | PRO £29.99/MO |
|---|---|---|
| Draw foul and surface water networks over a PDF, image or DXF plan | Yes | Yes |
| Auto-design by Colebrook-White and the Modified Rational Method | Yes | Yes |
| SuDS: permeable paving, rain gardens, swales, ponds, basins and soakaways | Yes | Yes |
| Water quality, interception and long-term storage checks | Yes | Yes |
| Sewers for Adoption, Welsh SuDS, Scottish, Part H and BS EN 752 checks | Yes | Yes |
| Long sections, schedules, quantities, pumping stations and BRE 365 soakaways | Yes | Yes |
| Import SWMM, LandXML, DXF and CSV, and the 3D view | Yes | Yes |
| Pipes per project | 20 | No limit |
| EPA SWMM simulation of every storm | No | Yes |
| Design by simulation and storage sizing | No | Yes |
| Coupled 1D-2D flooding, hazard maps and flow paths | No | Yes |
| Drawing sets and the calculation pack | No | Yes |
| LandXML, IFC4, Excel, DXF and SWMM .inp exports | No | Yes |
Coupled 1D-2D flooding on an exceedance test (Pro)
Yes, to design. Drawing foul and surface water networks, auto-design by Colebrook-White and the Modified Rational Method, the SuDS components, long sections, the 3D view, water quality and storage checks, every rule set, pumping stations, BRE 365 soakaways, imports, schedules and quantities are free, for networks up to 20 pipes. Drainage Design Pro is a Microsoft Store subscription (£29.99 a month or £249.99 a year, first week free) that adds SWMM simulation, design by simulation, storage sizing, coupled 1D-2D flooding, drawing sets, the calculation pack, the exports and unlimited pipes.
Source control (permeable paving, bioretention, rain gardens, green roofs, infiltration trenches, swales, filter strips and water butts) is modelled with the EPA SWMM LID models, each taking a share of its catchment's runoff. Storage covers ponds and wetlands with a permanent pool, detention and infiltration basins with side slopes, soakaways and geocellular tanks. Swales, filter drains, channels and culverts carry flow, with seepage. Flow controls are vortex controls (generic or your manufacturer's curve), orifices, penstocks, overflow and V-notch weirs and flap valves.
EPA SWMM 5.2.4, the US Environmental Protection Agency's Storm Water Management Model, running dynamic-wave routing on your PC. It is public domain and is the engine several commercial UK drainage packages are built on. Pipe capacities in the simulation match the Colebrook-White design calculation, and a verification report in the app shows the engine checked against published tables and analytic solutions.
Import the FEH22 or FEH13 depth-duration-frequency file for your site from the UKCEH FEH Web Service, type the six FEH99 catchment constants, paste your own depth table, or add a recorded storm. Storms are built with the FEH/FSR summer and winter profiles for every return period and duration you choose, with your climate change allowance and urban creep.
Sewers for Adoption (Water UK's Design and Construction Guidance v2.3), the Welsh statutory SuDS standards, Sewers for Scotland v4, Building Regulations Part H and BS EN 752. Checks include sizes, self-cleansing velocities, cover, gradients and access, surcharge and flooding by return period, exceedance, greenfield runoff rates and volume, water quality by the Simple Index Approach, interception, half-emptying times, infiltration safety, side slopes and freeboard. Each result gives the clause reference, what was found and what is needed, and you can change values, switch rules off and add checks. The guidance text itself isn't reproduced, and it's a design aid: the engineer stays responsible for the design.
With Pro, a coupled 1D-2D run puts one storm through EPA SWMM and a 2D surface model together (the local inertial scheme used by LISFLOOD-FP): water that surcharges out of a manhole or basin spreads over the ground and flows back in wherever the pipes have room. It runs on Environment Agency LIDAR terrain you import as an .asc grid, a LandXML surface, or a surface built from your cover levels, with buildings as walls and, if you want, direct rainfall on the ground. It maps the maximum depth, velocity and hazard rating (FD2320), with an animation, and finds overland flow paths and ponding hotspots.
It opens SWMM .inp files, LandXML networks and surfaces, DXF drawings (as a background or converted to pipes and manholes) and CSV schedules, and traces over PDFs and images. With Pro it saves LandXML for Civil 3D, IFC4, Excel with live formulas, DXF, SWMM .inp, drawing sets on A0 to A3 and a calculation pack ready to print to PDF. Projects are .m2drain files.
No. Projects are .m2drain files on your PC, the simulation runs locally, and there's no account to create.
