I understand the intangible benefits of a rain barrel, I really do. But times being what they are, I decided to compare the cost of a rain barrel to the money I might save by not using man made water. Let's see how a fifty gallon barrel adds up. In order to estimate the payoff period for my rain barrel, I had to do some math. How much money do I save when I use "free" rain barrel water instead of "man made" water?

How much does water cost?

This will vary of course. According to Circle of Blue, water is cheap. The organization estimates that "50 gallons per person per day for washing, drinking, cooking and flushing-[costs] less than $25 per month, which is a relatively small portion of a family budget. " Four people times 50 gallons is 200 gallons per day at under a dollar per day. Let's just round it and call it a dollar for 200 gallons. That means our fifty gallon rain barrel holds just 25 cents worth of water.

How many fills of the barrel will you use? That may depend on how many fills you get.

You need rain to fill your barrel. A chart from weathertoday.net lists over 200 U. S. cities and the average number of days with some measurable precipitation for each city. I hope you don't live in Yuma, Arizona. Your rain barrel may get filled only 17 times this year. For this exercise, let's use a city in the middle of the range of rain days: Baltimore, Maryland. Baltimore has approximately 114 days each year with precipitation of 0.01 inches or more. Now let's assume they are evenly spaced throughout the year, with half occurring during the approximately six months that a Baltimorean may be doing some sort of gardening. That's 57 "rain days" in six months, or about ten a month. That gives us a rain day every third day. Sure enough, this record of observations for nearby Millersville Maryland shows rain on five of the last fourteen days in this area. Let's say that each rain event fills the barrel and that water is used each time. (These are generous assumptions that give the most favorable results possible; note that Millersville's rain occurred in two separate periods with four of the days being consecutive. In reality this rain would yield two usable full barrels at best, in my mind. ) 57 fills at $0.25 per fill yields a savings of $14.25 on water for one gardening year, given average, evenly spaced rain and average water costs.

What's the payoff period cost of the system?

Here's the bad news. Those pretty rain barrels in the catalogs can easily cost a hundred dollars or more. They come in a multitude of shapes and styles to match every suburban dream home or rural retreat. Yes, they are pretty... and pretty pricey too. You can spend hundreds of dollars on a rain barrel! And that's not all. Does it need a stand so you can actually get the water out? 50 bucks. Do you need a special diverter doohickey on your downspout to get water IN the barrel? That might run you another thirty or forty dollars. For this discussion, let's say you'll spend 150 dollars to get set up with a fifty gallon barrel. I estimated above that a fifty gallon barrel saves about $14.25 a year in water costs. At that rate this barrel will take eleven years to pay for itself. I would be very surprised if all the fittings and parts last eleven years without replacement.

My conclusion: rain barrel payoffs may be intangible at best

There are benefits to installing a rain barrel, both to the gardener directly (convenience, garden fashion, etc.) and to our physical environment (conservation of pure water, reduction in runoff and pollution, and more.) Please do the math for your own situation and adjust the calculations for your water costs and rainfall patterns. (As this article "went to press," I learned from my local newspaper that city residents will soon be paying approximately $106 per month for the water I estimated at $25 above. Clearly, with water costs quadrupled, the payoff equation changes.) My conclusion is that the dollars and cents benefits of a rain barrel clearly indicate that the more expensive barrels simply may not pay for themselves. If the garden budget is tight, seek the cheapest rain barrel system.

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For further reading:

Geoff Stein make a good case for some intangible benefits of rainwater in his article, "The Magical Properties of Rainwater."

Darius Van d'Rhys gives instructions in "Making a SImple Rain Barrel"

Paul Rodman wrote "Roll out the barrel, the rain barrel that is! (more rain barrel instructions)

Circle of Blue, http://www.circleofblue.org/waternews/ accessed 6-25-2012

"Despite the hand wringing over prices, water in the U.S. remains cheap. In most cities surveyed by Circle of Blue a family of four can buy enough water for its indoor needs-50 gallons per person per day for washing, drinking, cooking and flushing-for less than $25 per month, which is a relatively small portion of a family budget. "http://www.circleofblue.org/waternews/2010/world/the-price-of-water-a-comparison-of-water-rates-usage-in-30-u-s-cities/

Intellicast http://www.intellicast.com/Local/ObservationsSummary.aspx?location=USMD0271 accessed 6-25-2012

Weather Today http://www.weathertoday.net/weatherfacts/precip_01.php accessed 6-25-2012