More Reading:

Rainfall Density in the United States

Refer to plumbing code for rainfall density in different locations in the United States.
Or, website of National Weather Bureau (NOAA)

Roof Area Calculation

Sizing Roof Drains:

More references: J.R. Smith's Technical Data "HOW TO SELECT A ROOF DRAIN" (Note: link may change).

Storm Drain Sizing

Roof Drains/Leaders
Rainfall Rate (mm/hr)Area (m2)Flow (L/s)Pipe Capacity (m2) Drain Dia (mm)Safety Margin (%)
Horizontal Piping
Rainfall Rate (mm/hr)Area (m2)Flow (L/s)Slope(%)Pipe Capacity (m2) Drain Dia (mm)Safety Margin (%)

Warning! Different plumbing code has different maximum roof area for a particular roof drain and/or pipe size. Be sure to check the plumbing code enforced in your project area.

How to Use:

PlumAL can do more:

Return to Main Menu
Product Selection