How to harvest rain for your yard
After a soggy October, a rainy winter – hopefully – may be on the horizon. Or maybe not.
Given that uncertainty, how do you save some of that free water for possible dry days ahead? Those extra gallons could come in handy, especially if we face another year of drought. Current forecasts seem to point toward La Niña conditions and a subpar water year.
Rain barrels and cisterns allow for on-site storage of rainwater, a boon for homeowners facing watering restrictions. Regardless of drought conditions, saving rainwater can make sense for any gardener. Plants like rainwater, which is naturally soft and chemical-free. And if you usually get your water through municipal pipes, it saves money as well as water.
After five years of drought, rain barrels and equipment are easier to find at major home improvement stores and local nurseries. Before you dive into barrel use, here are some factors to consider, provided by GrowWater.org and other rain harvesting experts:
What’s the difference between a rain barrel and a cistern?
Rain barrels pretty much fit their name; they’re barrels or small tanks designed to catch and hold rainwater. Typically, they hold 40 to 80 gallons and cost under $200.
Technically, a rain barrel acts as a small cistern – a reservoir or tank for holding rainwater for later use. Most home cisterns are larger storage tanks, capable of holding 1,000 to 3,000 gallons. They can be quite large; a 2,000-gallon cistern is about the size of a minivan. A 3,000-gallon tank is 8 feet tall and 8 feet wide. Cost ranges from $1 to $3 per gallon for above-ground tanks, $3 to $8 per gallon for below ground.
What do you need?
1. Your roof should have a gutter system and downspouts. The roof serves as a catchment area to harvest the rainwater, and the gutter system quickly directs the water off the roof via the downspouts. When placing a barrel, choose a downspout that’s closest to your garden area, so any overflow will irrigate your plants – not run off down the street. Also, make sure the overflow won’t pool next to the house’s foundation.
2. The barrel or tank should have a debris screen and lid. The screen can be as simple as removable wire mesh at the end of the downspout or on the top of the barrel, helping to keep leaves, pine needles and other debris from collecting inside the barrel, where it can clog the outflow. A tight-fitting lid keeps debris, light and bugs out of the water, too. It’s also important to protect children, who might be curious about a barrel full of water.
3. A downspout diverter lets you “harvest” the rain by redirecting water from the downspout into the rain barrel or cistern. If the tank is full, an automatic overflow control directs water back to the downspout.
4. Hook up the downspout to a storage tank. This can be one rain barrel, several barrels in tandem or a larger cistern. The tank should be opaque; any light will invite algae growth. When filled, that tank will be very heavy; 50 gallons of water weighs 415 pounds. To get better flow out of the tank, elevate it 12 to 18 inches off the ground.
5. A hose or bucket lets you use that saved water and direct it where needed. Hook the hose up to the spigot at the bottom of the barrel.
▪ Don’t let your barrel become a mosquito hotbed. Mosquito control rings or other mosquito bait keep mosquitoes from breeding. So does that tight lid.
What about maintenance?
Monitor your barrel for debris, algae and mosquitoes. Keep the debris screen clean. If algae becomes a problem, empty the barrel and wash with a diluted bleach solution. Every two or three years, wash out the barrel with soap and water.
If properly stored and used within six months, rainwater shouldn’t go “bad.” Unscented bleach may be used to keep the water and barrel sanitized. Add two tablespoons of bleach to 50 gallons of water once a month.
If temperatures drop into the 20s, don’t let water in the barrel freeze. It may crack the barrel. Protect it from freezing with a thermal blanket or empty its contents.
How much water can you harvest?
One inch of rain on a 1,000-square-foot roof can yield 623 gallons. A half inch totals more than 300 gallons.
To figure out your potential harvest, measure the section of roof that will drain directly to a barrel. Then, do the math: Multiply the square footage by inches of rain by 0.623, the conversion factor to gallons. For example, a 20-by-15-foot roof section yields 47 gallons per quarter-inch of rain – enough to almost fill a 50-gallon rain barrel.
There’s potential for a lot of free water – especially during a “normal” winter. Historically, Sacramento’s annual rainfall is 18.5 inches. A rain harvesting system on an average 1,360-square-foot roof could yield more than 15,000 gallons. Even in a drought year such as 2014, Sacramento received 10.35 inches. That adds up to more than 8,700 gallons from that average-sized roof.