This simple system stores enough water for my plants during the current California drought. It has been in place for over six years and consists of two rain barrels under roof downspouts, with 15 garbage cans between them. About an inch of rain fills all the containers yielding 570 gallons of rainwater storage. Our coastal fog (as seen in the background), slowly drips from the roof, and provides gallons and gallons of water with no rainfall, during the summer.
Tip: These dark colored garbage cans start leaking after a few years from being in the the sun, and last much longer sheltered with a redwood cover like the one shown here.
Overflow water from the barrels goes into garbage cans using short sections of garden hose. Drill hole into top of lid.
Each adjoining garbage can is connected by drilling holes into the sides and inserting a section of garden hose. Drill holes a little bit smaller than the diameter of your hose and a fraction of an inch lower in the side of each additional can.
Tight fitting lids keep out mosquitoes and other varmints.
Dip in to fill up a watering can or pump out using a submersible pump.
This setup is handy for drenching plants in cans or soaking in inverted lids full of water.
Almost any downspout can be put to use collecting rainwater.
Ready made barrels are available (about $80 – 100), but it is easy to make your own using used salvaged food barrels if you can find them ($15-20 in materials).
After a few years of draining the system overflow rain away from the house, we added this 550 gal tank. Once all the barrels and garbage cans are full, we open up the low faucets on the two downspout barrels, which have connected hoses flowing downhill to the tank. The barrels, then mostly empty, have the space to hold more water from the roof which then flows into the larger tank. This also prevents excess rainwater from flooding the area once the cans are full. This tank fills up with just 2 inches of rain.
Update: February 2016 – Added a 710 gallon tank, as well as more garbage cans to the barrels behind the greenhouse and in the dog yard. These two cans reside about 20 feet away from the barrel, overflowing through a hose downhill. With all the extra barrels and cans, we are now storing 2292 gallons of rainwater.