Saving and Using Rainwater
Groundwater resources in Florida face high demand for consumption, agricultural and industrial needs. Taking advantage of Florida’s seasonal rainfall can reduce pressure on groundwater for non-potable uses during drier seasons.
For the homeowner, harvesting rainwater reduces your water bills and allows you to use the stored water at your discretion. Because it’s not public water, you don’t have to follow water restrictions.
Depending on your water needs and the amount you want to store, you can incorporate rain gardens and ponds, rain barrels, or cisterns into your landscape.
Rain gardens are water retention zones for drainage. They help prevent erosion and runoff and can also filter out pollutants in surface water. Depending on the liner, the water stays in the garden until it’s used, or it percolates into the soil.
To plan your rain garden, take advantage of existing drainage. Place gardens where water already accumulates. Make sure the garden drains water away from structures to prevent flooding.
To build a rain garden, partially excavate the site, and then backfill with stone and gravel. Check local and homeowner’s association rules about whether or not you will need a liner or sump. You can also add a liner to turn the collection area into a pond, rather than a groundwater recharge area.
Landscape using resilient plants that can withstand periods of inundation and drought. Water the plants, mulch and weed the garden to ensure successful establishment. Once established, the garden should be relatively low maintenance. Supplemental irrigation during dry times will depend on plant choice.
Rain barrels can refer to any container that captures rainwater. They are usually large containers situated under downspouts to catch roof runoff. Rain barrels are fitted with screens over their openings to keep out debris and mosquitoes.
You can purchase a rain barrel or create one yourself. There are many online resources as well as information and classes offered through local Extension offices. Check the Extension calendar for any classes in your area.
One inch of rainwater per 1,000 square feet of roof will result in about 600 gallons of collected water. You can set up a system of rain barrels, each collecting overflow from the previous one in line, to hold the amount of water you want to store. You may want one rain barrel, or you may want ten.
Most people install spigots on their rain barrels and attach hoses to use the stored water. Depending on the elevation of the rain barrels, you can use gravity or pumps to move the water through the hose to where you need it.
Cisterns are a good choice for those who want a greater storage capacity than rain barrels provide. A 6’x6’x6’ cistern can hold 1,600 gallons.
Cisterns can be above- or below-ground or partially submerged. They need to be watertight, have enclosed lids, and be made of non-reactive material (e.g. reinforced concrete, galvanized steel or plastic).
More so than rain barrels, cisterns need good pre-filtration of rainwater coming from the catchment area (usually a roof). Regularly clean gutters and downspouts, and consider installing gutter guards. Do not collect water under overhanging trees.
Keep in mind you will need access to the inside of the cistern for cleaning. Other design considerations include an overflow pipe, a pretreatment zone with a screen and filter, screened input and outlet valves to control water flow, and weight load.
One gallon of water weighs 8.3 pounds, and a cubic foot, 62.4 pounds. If you have an elevated tank, make sure it is placed on a structurally sound platform.
Local regulations and construction costs may limit your cistern installation. Check with city or county offices to see what permits you may need. Also try searching for grants offered by community, regional or national organizations to help offset costs.
All of these methods are for collecting, storing and using water. Your stored water can be used for uses that do not require potable water. (Do not use stored water for drinking.)
A popular option is using the water to irrigate lawns and gardens. You can install a pump or use gravity to feed hoses. Another option is to just hand water. Make sure you set up your tanks for easy access to spigots, outlets or lids.
For gravity-fed irrigation: Every 2 ½ feet of elevation of the water source above the water outlet (e.g., the elevation of the tank versus the elevation of the garden) will create one pound of pressure. Keep in mind that friction in the pipe or hose will reduce water pressure.
Contact your plumbing or building department before connecting a pump, plumbing, or irrigation lines to see if you will need backflow protection for your potable water line. Do not connect your rain barrel or cistern to your in-home plumbing because of the risk of contaminating potable water.
Beyond watering your garden, stored water can be used to wash vehicles. Fill ponds, fountains and swimming pools, and used in home toilets and washers (check local regulations).
Harvesting rainwater is a great way to conserve water, decrease your water bill, reduce your impact on groundwater sources, minimize your vulnerability to drought, and create a sustainable landscape.
For more information on rainwater harvesting and water conservation, talk with your local Extension agent.
Adapted and excerpted from:
R. Bucklin, “Cisterns to Collect Non-Potable Water For Domestic Use” (AE64), Agricultural and Biological Engineering Department (rev. 03/2009).
“Capturing Water with Rain Barrels,” UF/IFAS Center for Landscape Conservation and Ecology (rev. 04/2009).
B.J. Jarvis, “Cisterns and Other Water Storage Strategies” (4.44MB PDF), Presentation, Master Gardener Statewide Conference (10/2010).