The coastal community of Small Point shuts down its water supply in winter, which forced Laura Sewall to find an alternative source of water. A well was one option, but the high mineral content in local groundwater would have required treatment. More than that, Laura did not want to interfere with the area’s delicate hydrological balance.
Factoring in supply and demand
In designing the system for Laura’s house, builder Christopher Hahn looked at the average rainfall for coastal Maine (about 4 inches per month) and calculated how much the home’s standing-seam metal roof could reliably collect. He used a formula that assumed a half-gallon of water would be collected for each inch of rainfall on each square foot of the home’s footprint. With a roof area of about 2200 square feet, the system would collect 4400 gallons in an average month. The four tanks hold almost twice that amount. With Laura’s water conserving fixtures and appliances, the system exceeds her needs during the months when there’s no other source of water.