Roll Out the Rain Barrels?

By March 15, 2011Sustainable Landscaping

By Owen Dell

From The Earthworm’s Lair: Owen Dell’s Sustainable Landscaping Blog

Rain barrels are the de rigueur item for urban eco-hipsters these days. They’re sold in every garden catalog, subsidized or given away by water districts, and touted by virtually every garden expert in creation as a way to reduce garden water use and be more “green.” There are rain barrel community workshops, rain barrel seminars, Web sites devoted to the emerging rain barrel culture, rain barrel discussion groups, rain barrel tweets, and, for all I know, rain barrel users dating services. Progressive gardeners who haven’t yet bought their barrel are made to feel wasteful and negligent for failing to acquire the latest in an endless series of products designed to save the planet. Thanks to relentless marketing, rain barrels are enjoying a potent dose of moral buzz that is fast turning them into a 21st Century version of the Great Tulip [1] Mania.

Photo by Eric Schmuttenmaer. Used by permission.

HOW RAIN BARRELS WORK. The rain barrel idea is simple: Stick a drum under your downspout to catch rainwater and store it for later use. This is supposed to help the environment, lower your water bill, and make your garden thrive in dry times. And to be sure, there’s no point in throwing away rainwater if you can make use of it. After all, once rainwater hits the street, thanks to the highly efficient drainage systems that landscapers put in, it causes urban flooding and washes all kinds of nasty pollutants into the storm drains and thence into our creeks and finally to the ocean. Using rain is smart; whisking it off the property is stupid. So there’s a good idea behind this, but how does it play out?

In the name of water harvesting, intrepid companies have developed a truly impressive array of rain barrels, some of them repurposed from previously-used containers, and most of them made new from fresh, modern plastic. They parade across the pages of garden catalogs and Web sites in a happy fashion show of forms: Spartan repurposed, faux Grecian Urn, faux wood, faux stone, faux ceramic, concealed plant stand, bogus whiskey barrel, real whiskey barrel, collapsible, roll-away, pop-up, knock-down, “mega” rain barrels, “eco” rain barrels, rain barrel “systems.” They come in various shades of green, earth tones, terracotta, robin’s egg blue (seriously), and basic black. alone delivers 897 listings [2] for rain barrels and rain barrel-related items. By and large they’re a homely bunch: Fanciful shapes and ersatz wood grain concealing the humdrum function of holding 50 to 65 gallons of rainwater. But if they really would help save the Earth, then who cares what they look like? After all, we’re in dire straits and can’t be troubling ourselves over matters of aesthetics, right?

YES, BUT DO THEY MAKE SENSE? Rain barrel proponents claim that barrels conserve water, reduce urban runoff, and save money. But is it true? Suspecting that a small flagon of rain wouldn’t begin to meet the water needs of the garden, and wondering if there was even a net positive outcome when the environmental impacts of making and shipping the product are balanced against the value of the water saved, I set out to get to the bottom of the barrel business.

Let’s begin with how much water is needed to run a typical garden. It’s a number that shocks most people, even experienced gardeners. According to the Metropolitan Water District [3], the average Southern California family uses about 234,000 gallons of water each year. Sixty percent of that, over 140,000 gallons, is used to water the yard. Using commonly available data on evapotranspiration [4]rates in coastal Southern California, the Green Gardens Group [5] calculated that a typical 1,500 square foot front yard on the South Coast with a lawn and some foundation plantings requires around 43,000 gallons of water per year. Looking further into the matter they found that, thanks to poor water management practices, typical water use is 2 to 3 times what is needed, with actual applied water often clocking in at over 100,000 gallons for the same small front yard.

So here’s a question: Which is better, to save 60 gallons of rain water by installing a rain barrel or to save over 1,000 times that amount simply by dialing back the watering to a reasonable level? Keep in mind that changing watering behavior costs nothing and delivers immediate and long-lasting results. In this instance, the mid-tier price of water in Santa Barbara is $4.90 per hundred cubic feet [6] (HCF, equal to 748 gallons), which means that saving 60,000 gallons of water will reduce the water bill by $393 per year. By comparison, that smidgeon of water in the rain barrel is worth just over 39 cents.

What about the practicalities of watering your garden with rain barrels? It’s easy to see that it would take a heck of a lot of barrels to meet the water needs of a typical garden. Going back to that 140,000 gallons of water used by the average suburban landscape, one barrel will supply .00043 of the annual water need, or as landscape professionals say, a drop in the bucket. It would take 2,333 60-gallon barrels of water to meet the annual needs for irrigation. Each barrel takes up about 12 cubic feet, so 2,333 barrels require 28,000 cubic feet of space. The interior space of a 2,000 square foot house with 8 foot ceilings measures around 16,000 cubic feet. If you were to stack your rain barrels to the ceiling, you would need a volume equal to 1.75 additional houses to store this much water.

If you were to place the barrels on the ground one layer deep, they would require 9,332 sq. ft. of land, which is just under a quarter of an acre. Since the average suburban lot size in our area is around .17 acre, you would need 1.47 more lots just to store the water. Oh-oh, it’s time to buy out the neighbors and tear down their houses so you can water your garden. This must be the reason that none of the respected experts on rain water harvesting advocate or even mention rain barrels in their books and publications.

BULLYRAGGING THE BARREL BARONS. Just for fun, I submitted the following good-natured inquiry to a couple of Internet rain barrel vendors:


I have a 7,500 square foot lot, and I use about 140,000 gallons of water per year for landscape irrigation. A single 60-gallon rain barrel will supply 0.00043 of my annual water needs, making it necessary for me to have 2,333 barrels to meet those needs. They will fill almost a quarter of an acre of land if placed side-by-side. My lot is only about .17 acres, and the house and garden take it all up. Do you have any suggestions? Thank you.

Rodger C. “Rod” Buck, Customer Care Variety Specialist at Hayneedle [7]wrote back, “Unfortunately, we are strictly a retail on-line web site that does not get into anything as heavy-duty as you are describing. May I suggest that you check with a local company that specializes in wells and/or in rural cistern tanks?” I guess the point was kind of lost on Rod. The folks at Gardener’s Supply [8] did a little better, and even played along with me: “Thank you for writing.  Our rain barrels are a great way to collect the free water from the sky, but as you have so eloquently pointed out, will not be a complete watering source for your garden. For small gardens, when rain is intermittent, they can be very helpful in aiding your watering needs.  They are intended to augment your watering, not take it over completely…we’d like to offer you a 10% discount. This is valid even if you want to order 2,333 barrels.” Sweet. I’ll keep that in mind if I ever take leave of my senses.

OTHER CONCERNS. Even if you had a one square-foot garden, which is what a barrel full of water will serve for the year, there are some additional issues that have to be looked at.

Suppose there isn’t enough rain to fill up the barrel? Just when you really need water most, your barrel is busy collecting dust and spiders. Not helpful. Not helpful at all.

If the barrel is located in the sun, you’ll be delivering potentially damaging hot water to your plants. Unless you like to cook your carrots while they’re still in the ground, this could very well be a problem.

How clean is the water? The first element in a real water harvesting system is what’s called a “first flush filter” that keeps contaminated water out of the system. You see, all sorts of guck collects on rooftops during our months-long dry season, and the first storm dissolves it all into a toxic soup that’s best sent down the drain. It’s not something you’d want to put on your plants. But the typical rain barrel, lacking a first flush filter, collects and stores the very most contaminated first part of the first flush. Please don’t invite me over for a taste of your rain barrel-irrigated spinach, OK?

Most barrels come with fine-mesh screens to keep mosquitoes from breeding in the water and prevent errant vermin from drowning in it. But of course the fragile screen will be the first part of the system to fail, and few owners will bother to replace it. How environmental is dead rat soup?

Is there a reasonable financial payback for the investment in a rain barrel? If the barrel fills 5 times a year, the annual value of the captured water is a little under two dollars. The cheapest available rain barrels cost around a hundred bucks, which means that the payback time for Santa Barbarans is at least half a century. It’s even longer where water rates are cheaper. In most cases, neither the barrel nor its owner can reasonably be expected to last long enough to see a return on the investment.

And what about the environmental impacts of making and disposing of the barrel itself? How much embodied energy is there in a rain barrel? Where do the materials come from? Is it recyclable at the end of its useful life? And how long could a barrel be expected to last anyway? Unfortunately, hard answers to these questions are not so easy to come by. Plastic is made from oil; we know that much. Although it’s often not spelled out, high-density polyethylene (HDPE) seems to be the material that most rain barrels are made from. HDPE is one of the least toxic plastics on the market, it will probably last at least ten years and possibly much longer, and it’s a #2 recyclable material. Beyond that, not much can be ascertained without fairly strenuous research beyond the capabilities of this poor writer.

GETTING TO THE BOTTOM OF THE BARREL. Is it possible to do a full life-cycle analysis on a rain barrel, to determine in hard numbers whether it’s a net environmental good or bad thing? Not easily, given the difficulty of obtaining some of the key data such as embodied energy, lifespan, and the impacts of oil drilling, and then putting it all together in a definitive bottom-line formula. But it should be pretty obvious that whatever the other variables, rain barrels don’t solve the problem of water conservation.

All in all, rain barrels are a washout, another delusional, greenwashed, pernicious consumer scam. Maybe the next rain barrel group should be Rain Barrel Abusers Anonymous. “Hi, I’m Darlene and I have 2,333 rain barrels.” “Hi Darlene!”

REAL SOLUTIONS. What’s a better use of resources? How can you really save water? Well, rainwater harvesting, done properly, is an essential element in a sustainable landscape. And yes, the amount of water you can capture can be impressive. A typical roof will deliver 600 gallons per 1,000 square feet of surface area per inch of rain falling on it. In real-world terms that means that an average Santa Barbara rainfall year’s 18 inches of rain landing on a 2,000 square feet roof will generate 21,600 gallons of water, which (in case you were wondering) is worth $141.00. In a nutshell, there are two basic approaches to water harvesting, both involving the canny capture of roof water.

Photo by Owen Dell. Used by permission.

NON-STORAGE STRATEGIES. One is to let rainfall flow across and sink into the soil, deep watering plants as it goes. This can be accomplished by changing the contours of your land to create low spots, soak zones, dry streambeds, and other concavities that will allow the water to pool and seep into the soil. (IMPORTANT ADVICE: Don’t try this on hillsides or where there is any potential for landslides, flooding of structures, or other untoward outcomes. And keep the water at least five feet away from the house. In fact, check with a geologist, landscape architect, water harvesting professional or other qualified expert before changing the grade on your property.) Concave, water-slurping landscapes are now required in some progressive communities, and properly done they make a lot of sense. Water stays on the land where it belongs, and the larger environment doesn’t suffer from the effects of dumping excess quantities of rainfall into the street. Creating a concave landscape is relatively easy and inexpensive if done at the time the landscape is created, but even an established landscape can often accommodate a swale, dry streambed, rain garden, or other absorbent zone. These are also very attractive additions to the landscape.

Photo by bloomsberries. Used by permission.

STORAGE STRATEGIES. Of course just moving and slowing water only works during the rainy season. Summer is another matter, and the rain barrel idea is a stab at addressing the issue of how to get access to water during the dry months of the year. Storing water does work, but only if you have the space and capital to create a fully-fledged system of one or more cisterns, which are above-ground or buried tanks. Do keep in mind, though, that rainwater takes up just as much room in a big tank as it does in hundreds of small barrels, so one of the big questions is where do you put the stuff? Unlike dry streambeds, cisterns are usually ugly, and they’re expensive, running between fifty cents and two dollars per gallon of storage capacity. That means that storing even 10,000 gallons of rainwater, a small fraction of what your garden probably needs, could easily run you ten or twenty grand [9]. You can buy a lot of water for that amount of money. Back to the question of where to put the cistern, well, you can tuck a lot of water under a deck, or put a tank out on the back forty (if you’re lucky enough to have a back forty), or dig a giant hole and bury the thing. Still, this is clearly not for everybody. But if you have the resources, a big slug of water on site is like money in the bank, keeping you soothed and safe. By the way, with the addition of a pump, a cistern can be used to fight wildfires too, which is never a bad idea in our flammable communities.

For more information on water harvesting, turn to the real experts. Brad Lancaster [10] and our own local genius Art Ludwig [11] both offer great, detailed advice on this surprisingly complex subject. Check out their Web sites for information, books, and other resources.

Oh, by the way, if you know of anyone who’s in the market for a couple thousand barrels, cheap, have them give me a call.

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  • Katelyn B says:

    It’s funny about how progressive and green water barrels are. My great grandmother used to tell me the importance of them and now it’s trendy. =)

  • Brandy Q says:

    What an excellent way to harvest natural resources that are available on your own property.

  • - says:

    The negligible capacity of barrels is obvious, but could be significant in frequent shower locations (eg, Guam). West coast has definite dry summers, so small water storage is significant only if overall water need are lower (aka ‘xerophytic’) Another use is ‘pure’ water for special plants in water districts with ‘minerally’ water (or well water).
    Btw, those two barrels in the photo appear to be a safety hazard. They are heavy and not restrained from falling away from the wall (is that a gate (implying a path) in the photo background?)

  • As our world continues to become crazier, people are looking for more ways to be self dependant. Water is an essential for life. Capturing water is a great idea for the environment and a great idea for being self dependant in the event our world continues down this scary path.

  • The biggest benefit of rain barrels for me is that they can often be situated so that it cuts down on the amount of “water lugging” I have to do around the garden. And of course it uses a valuable resource economically.

  • Paul says:

    Seems like a great idea that I could put to use this very day. Thanks for the tips!

  • Some of you maybe laugh, but my grand father had and used rain water barrels long before someone coined the term “eco”…so maybe we should look carefully in the past, there might be a trick or two that we can learn

  • It’s really a great and useful piece of information. I am glad
    that you simply shared this helpful info with us. Please stay us informed like this.

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