The catchment area can be any surface that water falls upon or any device that discards water.  Hard surface roofs, green roofs, and parking lots are a few of the most common catchment areas.  Others include synthetic turf, children's splash pads, cooling towers, and air conditioning units.

Rainwater from hard surface roofs can be used for:

  • Irrigation
  • Toilet flushing
  • Wash systems

Rainwater from parking lots and green roofs is typically used only for irrigation.  We employ various treatment methods if working with parking lots or greenroof water, in order to reach the standards for interior building use.  For example, below is an actual water sample from the green roof at Milwaukee's Clock Shadow Building.  The water has been dyed by the green roof media (soil) so we employed a chlorine recirculation and injection loop to improve water quality. 



The water quality of the harvested water reaches the desired level of clarity through chlorine treatment in the pictures below.


When looking at a potential rainwater harvesting site, one can assume 620 gallons of water per 1,000 square feet of hard-surface collection area per one inch rain event.  However, the world is an imperfect place and efficiency factors must be added to account for inefficiencies in the conveyance system and tank pre-filters.

Next Chapter:  Pre-Filtration