Size stormwater pipes and design pipe networks per AS/NZS 3500.3:2021. Uses the Colebrook-White equation for full-bore flow with PVC, concrete, HDPE, and more.
Enter catchment details and pipe properties to calculate capacity. Uses 5% AEP (20-year) rainfall intensity.
Add pipe segments to build a stormwater network. Each segment collects upstream catchment area and cumulative flow determines pipe sizing. Uses 5% AEP rainfall intensity.
Design flow is calculated from catchment area, rainfall intensity, and runoff coefficient using the rational method.
Pipe capacity is determined using the Colebrook-White equation, accounting for pipe material roughness and grade.
In a pipe network, downstream pipes cannot be smaller than upstream pipes. Cumulative flows determine sizing at each junction.
CCC Engineering delivers complete hydraulic design packages, including stormwater pipe networks, on-site detention, and connection to council infrastructure.
This stormwater pipe sizing calculator helps hydraulic engineers, civil engineers, and builders determine the correct pipe diameter for gravity stormwater drainage systems. Enter the catchment area, select your location for the design rainfall intensity, specify the pipe material and grade, and the calculator will determine the minimum pipe size that carries the design flow within acceptable velocity limits. The network design mode allows you to size a complete stormwater pipe system with multiple contributing catchments and cumulative flows.
Pipe capacity is calculated using the Colebrook-White equation for full-bore gravity flow, as referenced by AS/NZS 3500.3:2021. The calculator includes pipe data for PVC (SN4 and SN8), concrete, and HDPE materials with their respective internal diameters and roughness values. Design rainfall intensities are sourced from Bureau of Meteorology IFD data at the 5% AEP (20-year) event for a 5-minute storm duration. Velocity checks ensure the flow is above the 0.6 m/s minimum for self-cleansing and below the 4 m/s maximum to prevent erosion.
This tool is suitable for preliminary stormwater pipe sizing on residential and commercial projects. Final designs must account for pit losses, downstream tailwater conditions, on-site detention requirements, and compliance with the relevant local council stormwater management policy. For large catchments, flood-prone land, or sites requiring on-site detention design, consult a qualified hydraulic or civil engineer.