Sunday, October 17, 2010

Rain Barrels

I have been thinking about installing rain barrels off and on since we bought this house four years ago. There are many good reasons for installing rain barrels:

1) Save water for my gardens and lawn during dry spells
2) Prevent water from pooling in several places on our property during rainy spells
3) Reduce the amount of water that ends up in our basement/crawlspace
4) Possibly reduce seasonal expansion/compaction of soil around my foundation

Here's a link to a fun article about constructing homemade rain barrels.

However, there are a few obstacles I can't quite wrap my head around, the biggest one being capacity. We have a relatively small house; I estimate the roof to be only about 1000 square feet (horizontal surface area), counting the three porches. One inch of rainfall on this roof equals 83 1/3 cubic feet of water, or about 623 gallons. Typical big box store rain barrels only hold about 50-70 gallons of water each (and I understand this is a good idea, for safety reasons), so I would need about 9-12 rain barrels for every one inch of rain I want to catch. Average rainfall in my area between May and September is about 4.2 inches/month and falls in (my experience here) between 2 and 5 rainy periods per month. It seems like catching and using an inch of water at a time would (typically) be helpful, though there have been some storms this year that would scoff at such piddly storage capacity.

Now, where on earth am I going to put 9-12 rain barrels? And how do I distribute this water over my lawn/gardens several times a month? And ignoring both of those problems, to really address issues 2-4 I would definitely have to re-route a few downspouts. (Perhaps this is something I should do anyway, but what a project!) And how do I keep the infernal mosquitoes out of them? And should I worry about toxins from the roofing materials being distributed over my garden?

Of course, if tap water weren't so accessible and cheap I would probably have done this already. But being that it is both, I get a little overwhelmed thinking about the problem and keep setting it aside. Maybe this year, if we don't move....

Just for fun, let's try coming at the capacity calculation from the usage end. My lot is about 0.1 acre; subtracting the footprint of the house, about 3356 square feet. If I subtracted another 1000 feet of area that I just never water (the entire "front yard", the shed, a section we call "the back 40" that's outside the fence, plus some flowerbeds that are full of drought-resistant plants (a.k.a. the survivors of my watering laziness)), and assume the rest of it needs an inch of water per week (typical for established grass), that's about 1470 gallons of water per week. Of course, technically 4.2 inches / month of natural rainfall should be enough to keep all my plants happy, but the irregularity of the rainfall can be pretty gross. It would probably be safe to say that to keep a green lawn and fluffy soil I would have to water once every other week during the summer months, for a total of 2940 gallons of water per month. Hmmm...this is probably why I don't keep a green lawn!


  1. My co-worker Ryan has these on his house. He says the challenging part is keeping the mosquitoes away. But it all depends on how much water you will be using from the barrels. Also, he recommends connecting the barrels in series, and at varying heights, so that you have some pressure coming out. I agree that it would be a lot of work to set up.

  2. @Dr.BG - I was wondering if you would change your name! Anyway, do you think he would mind telling me his mosquito secrets? We do have problems with them already. I have used mosquito "dunks" in my birdbath in the past and wondered how well they would work / how many I would need in a rain barrel.
    (BTW, they didn't work too well in the birdbath, because the birds kept breaking them apart and knocking them out; finally I decided to just hose it out really well a couple times a week.)