Enter roof area, rainfall intensity and drain count to calculate total and per-drain rainfall flow. Use manufacturer flow-versus-head data for drain selection and capacity checks.
Roof rainfall demand
Flow demand only
Calculate total runoff and the demand per entered drain. Automatic drain size, scupper
dimensions, capacity, and ponding head are unavailable: these require a selected
product-specific published flow/head rating. This tool does not establish a code-compliant drain
design.