If I had to rank from most favorite to least all gardening tasks, watering from a hose would come in dead last. Rain barrels caught my attention a long time ago because they offer the opportunity to store water where its needed without too much assistance from a hose.
I started with a converted garbage can (bad idea). Then came an old compost barrel. Eventually, Santa Claus delivered two rain barrels one December morning. Then we added rain diverters to some downspouts. Finally, my rain barrel operation was in business and its been very helpful.
Though these devices seem simple, there are a few things you need to know. Otherwise, you may be like me and wind up reinventing your water collection operations a few times before you feel as though you “got it right.”
How to Select a Rain Barrel
There are four primary features you’ll want to consider: size, material, the lid and intake openings, and water distribution.
How Big a Barrel?
Say you have a 10 x 10 garden or 100 square feet. During the growing season, assume it will require the oft-quoted inch of rain per week. One inch of rain on 100 square feet of garden is about 62 gallons. (See the sidebar titled “How Much Water?” on this page.) A 60-gallon rain barrel would just about meet the need of that 10 x 10 garden for one week. So, let’s say it rained one week but not the next. Your stored water would give you what you need to get by in the dry week.
But how much water can be saved from the roof? Say it rains one inch in a week. If you have a 1000-square-foot roof (25’ x 25’) draining into your rain barrel, that inch of rain will actually provide more more than 600 gallons of water, much more than you need for a 60-gallon barrel. This is a good reason to hook up a second rain barrel to catch the overflow, a feature that most rain barrels offer. Now you can supplement nature’s scarcity with a generous 120 gallons – enough to last you for two weeks.
Use the rough calculations above and in the sidebar to estimate your watering needs. My own recommendation, based on experience with four rain barrels, is to get the biggest you can afford and fit into the available space.
Recommended Materials for Rain Barrels
According to most of the sources I've used, three features of the material should concern you: (1) type of plastic, (2) UV stabilization, and (3) color.
Is it made of food-grade plastic? Many rain barrels are made from recycled food barrels that contained juice, pickles, olives, and other comestibles. While the barrels cannot be reused for food, they are safe for rainwater collection.
If you’ve been following the news about plastics and microwaves, you may have read that all plastics leach some amount of chemicals into the materials they contact. This is particularly true of PVC (polyvinyl chloride) and polystyrene plastics when they are heated. PVC plastics carry the recycling number 3; polystyrene is number 6. If you outfit your own barrel, avoid PVC plastics (recycling number 3) and polystyrene (number 6).
Is it UV stabilized? Plastic ages in sunlight and heat, becoming discolored and more brittle with time. UV stabilizers lengthen life and improve the appearance of your rain barrels.
Is it the right color? Almost any color will do – if it’s not black or white. During the height of summer, when you need water the most, black plastic can retain too much heat. Hot water on a hot summer day can cook your plants. For this reason, homemade barrels of black plastic garbage cans are not recommended. White plastic food buckets are common and readily available but they’re not opaque. Within a week, you can get quite a lot of algae in a white bucket.
Rain Barrel Lid and Intake Openings
The lid is arguably the most important aspect of your purchase, for several good reasons.
Safety: Rain barrels have some hidden dangers. They MUST be covered at all times. This is because children, pets, and backyard wildlife may be attracted to them, fall in and not be able to get out. (Last year, for instance, a local squirrel went for his last swim in one of my rain barrels when I left it uncovered for just a few hours.)
Some rain barrels are fully sealed with only a screened, louvered 6” opening for water intake. There is one safety disadvantage to sealed models: the weight of the filled barrel. Since a rain barrel must be elevated to take advantage of gravity, a person or pet could be knocked over and injured by the weight of a full rain barrel. It must be placed in such a way as to prevent tip-over accidents.
Others have a solid screw-on lid with an opening. As for safety, a barrel with a screw-on lid is more likely to spill its water quickly in a tumble. Someone standing nearby might get wet, but they’d be unlikely to get hurt.
Some barrels have lids made entirely of screen. I don’t recommend screen openings, as they may be too weak to withstand the weight of a pet or a curious child’s hands. Screen also admits a lot of algae-producing light.
Mosquito prevention: No one wants their rain barrels to become mosquito nurseries, but it can happen! Mosquitoes, including the Culex mosquito that carries West Nile Virus, will breed in a barrel. The lid is the first line of defense. The sealed, solid lid with a screened, louvered opening is arguably the most effective mosquito screen, followed by screw-on tops with small, screened openings. A few drops of dish soap or olive oil will keep the water surface unfriendly to mosquitoes, as will mosquito dunks containing Bt. None of these will harm vegetables.
Cleanliness of rainwater: A good lid can keep small particles and bird droppings out. If it has not rained in a long time, you may want to avoid collecting the first flush of rain. Allow the rain to give the roof a good wash, then open up the downspout diverters and collect away!
Bottom line on lids: Careful choice can make a lot of difference in your ultimate satisfaction.
Rain Barrel Water Distribution
There are two features to understand in water distribution: barrel height and overflow.
Overflow, Hoses, and Barrel Height
Most barrels come equipped with an outlet near the bottom and a short hose. Manufacturers offer both brass and plastic fittings. (Brass is potentially longer lived.) You can certainly add hose length, but the farther your garden is from your barrel, the higher you’ll want to station it. This is especially true if you’re going to use it with a soaker hose or a sprinkler. In my experience, barrels must be at least 12” above ground.
According to Sharon England of Sky Juice New England, at 24” above ground a 75-gallon barrel can create enough pressure to operate a low flow hose.
Overflow: A good rain quickly fills a barrel, so you should only consider models that are equipped with overflow valves and hoses. These allow you to divert the overflow away from your house, or link another barrel to the first. Otherwise, water can pool up around the base of your foundation – an obvious drawback.
Helpful as they are, rain barrels are only one element of water management during long dry spells. Look at what happens during a 12-week drought: Your 10 x 10 bed theoretically needs 744 gallons over 12 weeks – the contents of ten 80-gallon rain barrels. Under these extreme conditions, rainwater collection is not likely to be the sole solution. Other strategies include drought-tolerant plant selections, 2” – 4” of mulch, and watering only in the early morning. If you have a sprinkler system, be sure to equip it with a water sensor.
Rain barrels can be great garden helpers. Just keep in mind some of the topics discussed here as you select and install your system.
For more information or to purchase rain barrels in southern New England:
Great American Rain Barrel Company: Beverly O’Keefe, www.riwaterlady.com, (401) 539-0667
A version of this article first appeared in July/August 2004, Connecticut Gardener.