California doesn't have any manual on rainwater harvesting or much other information on it. I asked John Coleman, a Director of East Bay MUD, why EBMUD didn't promote rainwater harvesting and he said it wouldn't work here because we don't get rainfall throughout the year. That struck me as even more of a reason to put one in.
I had a new roof and gutters installed in March of 2008. I wanted covered gutters so they wouldn't clog up and require annual cleaning. During the first big rain after the new gutters were installed I noticed how much water was running out of the downspouts. I knew that San Ramon faced droughts and more were predicted and this seemed like a waste of something that could be stored and saved.
I researched how much water would come off my roof during the rainy season. The formula is roof area (sq. ft) x inches of rain x .6. My total roof area, including the garage is about 1600 sq. ft. I concluded that I could capture over 10,000 gallons from 12" of rain. My first thought was to connect the downspouts to underground pipes feeding an underground storage tank in my backyard. While not infeasible, this would be very costly.
I started looking at above ground tanks, and they are very large. I figured I could split the system in two and put a 2000-3000 gal tank on one side of the house for laundry, and one on the other side for the lawn. A representative came down from EBMUD to evaluate my lawn watering system, and told me that I needed to adjust a couple sprinklers for better coverage and water earlier in the morning. She also told me that my lawn, which is less than 100 sq. ft., requires 270 gallons of water a day. Whoa, that way 3000 gallons of water would last a little over a week. So I gave up the idea of rainwater for the front lawn for the time being.
The laundry idea seemed more feasible, but I needed to find someone who knew how to put in a system like that here. I posted messages on a couple of bulletin boards and forums, and received two recommendations. My budget for the two systems was $6000, but I found out that would only cover the laundry system. I selected WaterSprout in Oakland to do the work, because their estimate covered everything from hooking up the tanks to the gutters, draining away the "first flush" or first half hour of rain to wash the roof, installing two 1250 gallon tanks so I'd have some side-yard parking left, adding a pump to draw the water from the tanks across my garage into my washing machine, and a three stage filtration system to remove particles and contamination from the water before going into the washing machine. The only thing I plan to add is a small, point-of-use, electric tank-less water heater for the laundry's hot water. Here's a link to a video of John Russell of WaterSprout giving me a walk-through of the system.
Why laundry? Well the washer is in the garage and easy to hook up an outside system. The washing machine is connected to the water by hoses that can easily be screwed on or off. So there's no connection between my home water from EBMUD and my laundry water. Washing machines don't use a lot of water. A typical large load is 40 gallons. I do two or three loads a week, which is about 400 gallons a month. 2500 gallons of water, which should be in the tanks in May at the end of the rainy season, should last 6 months, or until November when the rains start again.
My new rainwater capture system is the first to be installed in San Ramon, but it shouldn't be the last. The first rain in October will go down the first flush, but from then on I'll hook up my washer to the rainwater tanks and sing "Pennies from Heaven," on wash days.