A rainwater harvesting system collects rain from roofs and other surfaces, stores it and reuses it, typically for irrigation, toilet flushing, cooling or washing, reducing demand on potable water.
Parking structures have large roof decks, but runoff from surfaces that vehicles drive on carries oil, metals and sediment, so it needs filtering before reuse. Rain from canopies, solar canopies and adjacent building roofs is cleaner and easier to use.
System components
- Collection. Roof or canopy drains routed to storage.
- Pre-treatment. First-flush diverters and filters to remove debris and oils.
- Storage. Cisterns above or below grade, sized to rainfall pattern and demand.
- Distribution. Pumps and separate, labeled piping to irrigation or other non-potable uses.
Considerations
- Local plumbing and health rules govern reuse; see the plumbing code and local amendments.
- Harvesting works best where rain falls during the season water is needed.
- Storage can also count toward stormwater detention where rules allow.
The Parkonomics view
Rainwater harvesting turns a garage roof from a drainage problem into a small water supply. It pays best when there is landscaping or a car wash nearby to use it.
Related terms: Stormwater Detention, Green Roofs, Sustainability, Parksmart Certification, Solar Canopy