Attenuation Tank Sizing Calculator

An indicative first pass on the Discharge-to-Storage Ladder. It estimates storage volume and StormGrid crate count — your final design must be confirmed to the current Environment Agency allowances, CIRIA C753 and your LLFA’s permitted rate.

Impermeable area (m²)

Design storm depth (mm)

Climate + urban creep uplift (%)

Permitted discharge (L/s)

Critical storm duration (min)

StormGrid height

inflow volume (m³)

released over storm (m³)

StormGrid modules (95% void)

indicative footprint (m²)

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