Design tools

OSD calculator

Site EIA, council SSR/PSD rates and net detention volume - with live BOM IFD for design rainfall.

site

Site and rainfall

Catchment areas and design intensity. Your answers stay if you go back.

Australian postcode

Enter your 4-digit postcode

Live BOM IFD (10% AEP · 120 min). Intensity is auto-filled as depth ÷ 2 hours.

Design intensity (mm/hr)

Site area m²

Roof area m²

Grass area m²

Grass C

Dwellings

Results are indicative for early design only. Confirm sizing with a licensed plumber, hydraulic consultant, or GRAF Australia for site-specific conditions and council requirements.

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