Rainwater Harvesting Demonstration
Established June 21, 2006
Collection Surface and Gutters
Metal roofs are ideal collection surfaces, but 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.
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 is $500 and up.
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, 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 a 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 $6,000.
There are many options available from an economical pump that is for do-it-yourselfers to a more powerful unit that has an increased flow rate. The cost for a pump with a pressure tank starts at about $500.
Filtration and Sanitation
The filtration and sanitation system consists of three components: a five micron sediment filter, a three micron activated carbon filter, followed by an ultraviolet light sanitizer that can handle a flow up to 12 gallons per minute. Proper maintenance is critical. The sediment filter ($3) must be changed every month, the charcoal filter ($10) every three months, and the UV light bulb ($75) must be replaced every fourteen months whether it is burning brightly or not. Cost $800 and up.
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 chemicals.
How much rainwater can I collect?
Approximately 550 gallons of rainwater can be collected every 1,000 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 1,000, multiply by 550 and then multiply by the average annual rainfall in your area.
How much rainwater do I need?
A reasonably water-conscious person uses uses between 25 and 50 gallons a day, excluding any landscape needs. A family of four would consume around 40,000 to 80,000 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 7,500 to 15,000 gallons of rainwater in storage until the next rain.
How much does a system cost?
A typical system for a family of two or four would include one 10,000 gallon fiberglass tank, some type of roof washer or first flush device, and an ultraviolet light. A ballpark figure for this system is $10,000 - $12,000. The cost can be reduced by doing all or some of the work yourself.
- Bluebonnet Electric Cooperative
- Gonzales Underground Water Conservation District
- Guadalupe-Blanco River Authority
- Guadalupe County Groundwater Conservation District
- Lower Colorado River Authority
- Plum Creek Conservation District
In conjunction with Texas Cooperative Extension and the Luling Foundation