Water Reuse Handbook - the Public Building Commission of Chicago

Water Reuse Handbook
34 : Public Building Commission of Chicago
• A = Roof collection efficiency, ranging from 0.80 to 0.85
• B = Loss associated with absorption and wet surfaces - value of
0.08 inches per month has been used
• Rainfall is in inches and Roof Area is in square feet
See ARCSA Rainwater Catchment Design and Installation Standards
for more information and average annual rainfalls for various regions.
Step 3: Design the system to meet needs
When planning a rainwater harvesting system, demand (fixtures
that may use treated rainwater) should be balanced as closely as
possible with supply (source water) harvested to avoid wasting space
and money on a system that harvests and treats more water than is
necessary. Also, different sources should be examined to determine
which makes the most sense and will best suit the rainwater needs of
the building. The system engineer is best suited to determine which
sources are most advantageous to harvest.
Step 4: Continually adjust system as necessary
*The table summarizes the demand for rainwater harvesting
systems. It is not exhaustive of the potential sources or applications
for rainwater reuse, and are meant to be used as a starting point in
planning a rainwater harvesting system.
Planning for a Water Reuse System: Planning for Rainwater Harvesting
August 2011