Garden practices that incorporate rain barrels can minimize storm water runoff by retaining water for later use in the garden.
Rain barrels collect water that would normally flow directly off the roof through gutter down spouts and become storm water runoff. Retaining this runoff for garden use conserves water for plants during dry periods, saves the gardener time spent watering garden plants and provides a consistent supply of free soft (no chlorine, lime or calcium) water for outdoor use.
Rain barrels come in many shapes and sizes. It is best to select a barrel that is sealed to prevent children or animals from accidentally falling into the barrel.
Because they operate on a gravity-fed system, rain barrels usually need to be elevated on top of a single or double layer of cinderblocks or the like. The existing down spout should be interrupted at the correct height of the barrel’s water intake opening using a diverter and/or flexible tubing. These are readily available online from sources such as Spruce Creek Rainsaver or in some local nurseries and hardware stores.
Rain barrel installation using a diverter and flexible tubing downspout.
It’s critical to connect an overflow hose to the barrel. The water overflow hose should be able to accommodate excess water so that during a significant rain event water can exit the barrel without gushing out along the building foundation. Keep an eye on the barrel until it is determined that the barrel can accommodate a torrential downpour. If the barrel is handling a large expanse of roof, the overflow hole and pipe may need to be enlarged or an additional rain barrel may be connected to the original rain barrel.
The amount of rain that will run off the roof can be readily calculated using the following formula.
Sample Rain Calculation
Assume ½ inch of rain (.5 inch) on an 800 square foot section of roof
Standard value- 1 inch rain on 1,000 sq. ft. roof yields 623 gallons of water
800 sq. ft. x .5 in. x 623 = 249,200
249,200 divided by 1,000 - about 250 gallons of storm water runoff
If you have a 54 gallon barrel, it is very important to have an overflow pipe!
The contents of the barrel can be used for hand watering or may be connected to a soaker hose that is attached to the barrel’s spigot. If a soaker hose is connected, leave the barrel’s spigot valve open continuously (24/7), this will allow the water to infiltrate the soil at a slow pace.
If the barrel usage rate slows down over time, shingle dust from the roof may have clogged the pores and accumulated in the soaker hose requiring the soaker hose to be flushed out by running water from an outdoor faucet through the soaker hose. Make sure the barrel has a fine mesh screen to prevent mosquitoes from entering and laying eggs. As an added precaution, a “Dunks” or similar biological pest control (Bacillus thuringiensis (Bt) 10%) may be tossed into the barrel to kill mosquito larvae. Bt is not harmful to pets, birds or insects.
It is not recommended that water from a “roof fed” rain barrel be used on food crops as roof shingles may contain undesirable materials. To winterize the barrel simply flip the diverter switch or disconnect the downspout and reconnect the old downspout. Finally, flip the barrel upside down. Accumulated sediment can be flushed out of the barrel by removing the mesh screen during spring installation.
Do-it-yourself rain barrels are popular and there are numerous sources of information on the internet. This short video clip, from the Penn State Three Minute Gardener, provides precise instructions for making your own rain barrel: Rain Barrels - The Three Minute Garderner
Spring 2013 Rain Barrel Lecture Notes: Rain Barrel Lecture Notes.pdf
Rain barrels are easy to install, maintain and use; they provide an effective way to conserve water and keep our watersheds healthy and our creeks, rivers and lakes free from contamination.