H&H is a leader in green building techniques in San Diego County. One of our techniques is implementing rainwater harvesting. What is it?

Since San Diego County has little rainfall, most of its drinking water is delivered via aqueducts and pumps. Rainwater harvesting is the concept that we can provide a portion of our irrigation needs through rainwater collection (and usually storage). The use of greywater (the water that goes down our drains) for irrigation also can assist these needs. These concepts are becoming popular in Southern California as a way to irrigate landscaping and gardens.

How to Harvest Water:
ROOF RAINWATER COLLECTION. In the City of San Diego less than 10” of rainfall for the average year on a 1,000 square foot roof adds up to 6,000 gallons per year of water that can be collected. Some regions of the county experience much higher rainfall and coastal areas can also collect morning dew from metal roofs. All this water is useful for irrigation and can be stored for dry spells, especially late summer droughts. Using gutters and downspouts to collection barrels, large tanks, or landscape collection basins are the common ways of collecting this water. Metal roofs are the cleanest surfaces to collect water from.

RAIN COLLECTION BARRELS & LARGE TANKS. Small collection barrels (50-200 gal) are easy to fit on your property but hold little water compared to large tanks. It makes the most sense to size a rainwater collection tank to be able to hold as much water as you may desire for dry parts of the year. Since your roof likely collects at least 6,000 gallons a year, you want a tank that can store as much of this as possible. Underground tanks cost more to install, but solve the problem of how to fit a large tank on your property.
LANDSCAPE DESIGN. The most affordable way to collect rainwater for irrigation use may be to design your garden with depression areas or swales where water can collect. Other alternatives? Dig deep trenches or small wells filled with gravel. Plant large areas of your yard where watering would be wasteful with native plants or other drought-tolerant plants – “xeriscaping.”
GREYWATER RE-USE FOR IRRIGATION. Greywater – water used for laundry, hand washing, and showering that can be re-used for irrigation. It is legal in San Diego to use laundry machine greywater to water plants without any permit needed! Did you know laundry uses more water than any other function in most homes? Use sodium & boron-free detergent to avoid harming plants if you go this route.
Do you want to learn more about Hubbell & Hubbell’s green building techniques? Visit our page about it here to learn more.
First image pictures 1300 gallon rainwater collection tank with mosaics by Alex Miller.