Rainwater Harvesting



Why collect rainwater?
Rainwater is the gold standard.  Unlike well water, it has zero hardness.   Less soap will be needed for your clothes, dishes and body, and calcium will not collect on faucets, tiles, glassware and hair.  If you size your system correctly, your rainwater supply is as dependable, if not more dependable, than a well.  Rainwater can easily be made safe and potable without the use of any chemicals.

How much rainwater can I collect?
Approximately 550 gallons of rainwater can be collected for every 1000 square feet of collection surface per inch of rain.  To estimate amount collected in one year, take the square footage of your collection surface, divide by 1000, multiply by 550 and then multiply by the average annual rainfall for your area.

How much rainwater do I need?
A reasonably water-conscious person uses between 25 to 50 gallons a day, excluding any landscaping needs.  A family of four would consume around 40000 to 80000 gallons per year.  The key to always having a supply of rainwater is to store enough water until the next rain.  Depending on usage, a family of four would need 7500 to 15000 gallons of rainwater in storage until the next rain. 

How much does a system cost?
A typical system for a family of two to four would include one 10000 gallon fiberglass tank, some type of roof washer or first flush device, a pump, filters and an ultraviolet light.  A ballpark figure for this system would be $10000-$12000. The cost can be reduced by doing all or some of the work yourself. 

Collection Surface and Gutters:
Metal roofs are ideal collection surfaces, but structures with asphalt shingles, clay tiles and even cedar shingles can be used.  Estimate the size of the collection surface by measuring the area of the footprint of the house.  Gutters should be screened to prevent large debris from entering the system.

Roof Washer:
A roof washer screens out gunk before it can enter your tank or else diverts the first, dirtiest wash or water from the roof.  It is a critical component of potable systems and is also needed to filter out small particles.  A wide range of equipment is available for different flow capacity and maintenance requirements.  Cost $500 and up.

Collection Tank:
A fiberglass tank may not be as handsome as a metal or stone cistern, but it provides versatility, hardiness and affordability.  One great feature is that the fittings are integral to the tank, so there is no risk of leaking at these vulnerable locations.  Also, fiberglass tanks can be painted with latex house paint to either camouflage or celebrate their appearance.  When placing your tank in position, remember that water weighs over eight pounds per gallon.  A 10,000 gallon tank weighs over 40 tons, so it needs to be placed on a smooth, level, stable foundation.  The cost for a fiberglass tank made with resins approved for potable water storage is about $6000.

There are many options available, from an economical pump that is great for do-it-yourselfers to a more powerful unit that has an increased flow rate.  The cost for a pump with a pressure

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