Roof Rainwater Collection:

There will always be some years when we have low-precipitation seasons or, in some cases, severe drought conditions. During these times, whether you are using city or well water, conservation is the name of the game! For avid gardeners a lack of water means watching your garden die before your eyes. Not a pleasant sight. So what can you do to save your garden and still conserve water? Collect and store what rain we do receive and use it during the dry months.

One Master Gardener, Al Dahlstrand, does just that and has kept his lovely garden growing through drought and low rain years. Al recently walked me through the garden and showed me how his roof rainwater collection system works. It´s simple and very cost effective.

The system was installed in 1990 due to lack of sufficient rain to keep the garden growing without using public water or drawing down the private well. (The house is on public water and the garden uses well water.) The components of the system include three used plastic tanks measuring 4´ in diameter x 4´ in height—each with a capacity of about 380 gallons for a total of 1140 gallons. A fourth tank has a capacity of 120 gallons. Al´s biggest challenge in installing the system was to place the tanks where they would be out of plain sight (relatively) but could be below the level of the back patio and high enough to not require much pumping to get water to garden areas. The smaller tank was placed in the front garden between several Toyon bushes and a lattice front. The three larger tanks were sited downhill of the back patio where the large vegetable garden is located. All tanks have covers, which keep small mammals from getting into them. A storm producing ½ to 1 inch of rain normally fills the front tank and about 50% of the three larger tanks.

Getting the roof rainwater into the tanks is accomplished by the use of plastic pipe, 2” PVC pipe and assorted connectors. Rainwater flows from the roof gutters to downspouts connected to the PVC pipes, which are connected to the tanks. Some of the PVC pipe going to the tanks is underground due to grade change and walkways.

Watering from the tanks is done using a ½hp electric sump pump through a hose and sprinkler, which is moved manually during watering. The front tank waters the small front lawn and neighboring shrubs. The back tanks are used to fill watering cans for hand watering of various shrubs and the vegetable garden or to the back lawn/fruit trees and various shrubs and roses. The lawn, fruit trees and shrubs can be watered simultaneously with an installed drip system. During the drought years, lawn that was not near fruit trees or other shrubs was allowed to dry up, but it came back the following winter.

While Al´s system may not hold enough water to irrigate his garden for the whole summer, it does provide enough water to help plants survive through the late spring and early summer during drought or light rain years while conserving well water for usage only during late summer and fall.

Al also collects rainwater from the roof of an outbuilding into 50-gallon drums and ladles it out to water shrubs and trees. This method of collection would work well even for a small city garden. Having a 30 or 50-gallon plastic trashcan at each down spout, a gardener would have water to use in time of need. Add a spigot to the can and you have easy access to filling a watering can or attaching a hose. (By the way, most potted plants will do better with rainwater than city water as there is no salt buildup in the soil due to the chemicals used in treated city water.)

Supplies (piping, connectors, sump pump) for a rain collection system can be purchased at any home improvement center. The tanks can either be purchased new (prices range from $300.00 for a 300 gallon tank, $400.00 for a 550 gallon tank and $600.00 for a 1100 gallon tank) or you may be able to find used tanks at a much lower cost. (Al´s large tanks were salvaged from the Carson Hill Mine, which was shut down around 1990.) If you do install used plastic tanks insure that they have been thoroughly cleaned prior to use. Even used septic tanks could be utilized as long as they have been completely cleaned.

The Master Gardeners are currently looking for used tanks that might be donated to use in the installation of a rain collection system at the Master Gardener´s Demonstration Garden. When we have the tanks, Al will hold an installation demonstration that is sure to be an instructive and informative class. Watch for the new 2008 Master Gardener Demonstration Schedule as to the date.

Carolee James can´t wait for her new rainwater collection system to be installed. It´s on her husband´s To Do List, but he won´t know that until he reads this article!!