Tuesday, March 17, 2009

Rain barrels

Feeling bold, yesterday I reconnected two of our eight rain barrels, a small rite of spring. Undeterred by the snowstorms of the last few days, I think spring is here and but just to be sure, I only reconnected the south facing ones. This time of the year we are not watering too much anyway- mainly we will be watering our compost pile, which did not freeze this winter (thanks to my wife- our compost maintenance supervisor). And hopefully, very soon, we can begin to water plants I will pot up when I start digging the foundation for my greenhouse.

Harvesting rainwater is a fun and easy way to save water and conserve one of our most important natural resources. You don’t need to invest a lot of money or excavate your entire yard to install a 10,000 gallon cistern with a solar powered pump to get going in rain water harvesting (though I’d like to). For as little as $100 you can get a few barrels, hours of fun, and a lot of water. This will probably not be enough to fulfill all irrigation needs so it is important to consider other aspects of conserving water in your landscape and around your home, but it is a start.

Other states and locations are way ahead of us in the inter-mountain west (Texas and Portland, OR are great examples), and two of the main things that deter people here from doing more with rainwater are the semi-arid conditions, and winter. Don’t let either discourage you. In fact, because of our dry climate it is even more critical to conserve the rainwater we do get.

How much water can you get?
A lot. This is the amazing thing, even in the dry climate where I live, where much of our 13" of annual precipitation falls as snow (and, thus, largely unusable for a budget-rainwater-harvester like myself), you can harvest quite a lot of rain.

I created a simple spreadsheet to calculate the amount of rainfall you could harvest from your roof and how quickly it would take to fill your rain barrels. Using this, I calculated that we get about 7.75” of usable rainfall, that is, precipitation from April through September during the growing season where we don’t have to worry about winter. The rest of the year- from October through March- I disconnect my rain barrels (see photos and discussion below) because of our water use and freezing. That 7.75" of precipitation translates into over 4,500 gallons of water. And, it only takes 1/2” of rain to completely fill our 8 rain barrels- over 400 gallons of water.

In the spreadsheet there is a worksheet that lists monthly precipitation for a few hundred US cities to help you calculate your own scenarios.

How is harvesting rain water "conservation", rain just goes into the ground anyway?
By capturing rainwater from the downspouts of your home you can store it and apply it directly toward plants or other elements in your landscape. As a result, it does not end up like the majority of rainwater coming off roofs. This water typically ends up in storm drains or sewer systems. Once in the wastewater systems, it will get stored, treated, filtered, processed, chlorinated, fluoridated (or some combination, depending on where you live), and again stored and then supplied back to you. This is resource and economically intensive.

Rainwater is better for your plants
There is really no need to use tap water -water that is treated and suitable for drinking, for watering your landscape- whether it is your vegetables in your garden or ornamental plants in your yard. Water comes from the sky just as the plants like it. In fact, rainwater is better for your plants- it is warmer and does not contain chlorine or other chemicals. Groundwater in our area is between 45-55 degrees F- this is too cold for many vegetables. Stored rainwater can be considerable warmer.

Where do you get rain barrels?
There are a lot of options here, and a lot of information suitable for a whole series of posts in itself (maybe I’ll do one at some point). There are many online garden stores that sell rain barrels already assembled. And there are plenty of websites with information on how to build your own- and there are some great sites out there. Just do a search for “rain water harvesting” or “build your own rain barrels” or something similar. Susan Tomlinson has had some recent posts with creative rainwater harvesting devices at the Bicycle Garden.

Building your own rain barrels is easy to do and a fun and rewarding project. I built ours out of recycled, food-grade plastic 55-gallon olive barrels- some had olives, pickles or garlic in them at some point, and they smell great. These sell for around $25 each.
What do you do in the winter?
In warmer climates, rainwater harvesting is a lot easier and a lot more efficient (so is solar hot water heating, but that is another story). Winterizing is an issue, and it is something you need to plan for in the beginning. As you can see from the pictures, in the winter I removed the two short elbows that connect to the rain barrel and replace it with a longer length of downspout material in the spring I do the reverse (see photo above). It only takes a couple of minutes. After disconnecting the rain barrel from the downspout, empty the rain barrels and store them for the winter. If you do not disconnect the rain barrels, you would have a heavy mess. The barrels would freeze solid all winter, probably break a few components, if not the whole barrel, and snow-melt runoff from the roof would likely lead to some crazy ice formations. But, I digress, you can also use a diverter, so you don’t have to remove and replace sections, but my system is pretty simple and allows emptying and inspection.


  1. David,

    I've 4 barrels to make for a customer, I'm a handyman by trade. Thought about these water saver devises, but they are cheap plastic and $30 to $70 a piece. Guess I'll just run a hose to drain it into their regular drain

  2. Hi randy,
    Thanks for the comment, but I am not sure I follow you. Are you saying you found some diverters that are not worth the money?
    Let me know if you have any questions about building rain barrels- I've been really happy with how mine have worked.

  3. Great post. Living in Idaho in the desert we really ought to have some of these. (I'll see if I can get hubbie on it.) :-)

  4. Excellent! I like it that you've got yours up on the cinder blocks, too--I need to do that to improve my gravity feed, which is really pathetic right now...

    It's amazing how much water you can collect, and in such a short time. Lovely.

  5. Thank you for posting this information. I am looking to do this for the company I work for and it is great to see the spreadsheet and all the Missoula related information so I know that it is not only feasible but a great idea for my company to try to implement!

  6. Excellent info. Harvesting rainwater is rare in the Phoenix area, probably because most of the rain we get comes in just a couple of months, so it's likely that the barrels would fill just once or twice a year. Another interesting thing is although we have an abundance of sun--350 days a year, solar panel use is also rare. Still too expensive.

  7. Great information! My question--any chance of mosquitos breeding in the tanks?

  8. Hi Daffodil,
    Thanks for your comments. Good question. Yes, mosquitoes can breed in the barrels. I screen the opening at the top two ways- one with a coarse screen for leaves and other stuff from the downspouts and below that I use standard fiberglass window screen to keep out mosquitoes. It sounds more complicated than it is. Maybe I should make a post on how to build a rain barrel?
    Thanks again,

  9. Hi Aiyana,
    Thanks for your comments.
    I agree solar technology is quite expensive and depending on the situation it can be prohibitively expensive.
    However, I must disagree about harvesting rainwater in your area, for at least three reasons. In a desert climate it is even more imperative to conserve water and harvest rainwater- you are living in a water-limited environment, and by nature, people use more than is naturally available so it has to come from somewhere. In the near term there are serious water shortage issues facing the desert southwest.
    The quantity of precipitation you get there is the same as the useable precipitation I get here- almost exactly (7.75” here vs. 7.66” in Phoenix) because you do not have to contend with winter and freezing temperatures. So even in a small house you could get thousands 4-7,000 gallons of water a year.
    Also, since you do not have winters, there are many technologies (rainwater harvesting included) that are much more feasible and cost effective, such as open solar hot water systems.
    The reality is water is a scarce resource.
    Thanks again for your comments, I am sure many have the same thoughts as you, so I am glad you brought it up.

  10. David, Yes please do a How To post on building rain barrels. A bit late in the day for me in CA, but I kinda think we'll have some rain again in the fall.

  11. I just found your blog via Gardening Gone Wild. It's great and I'm enjoying reading your posts.

  12. Hi Heirloomgardener,
    Thanks for your comment- I am glad you found my blog and are enjoying it!

  13. I also like using rainwater because it’s more “natural” than tempered water. I use droplet feeding for my plants. It’s easy to do, and all you need is just a long hose with pin-sized holes, a 2nd faucet, another barrel to connect the other end and voila! A ready made droplet feeder to continuously feed your plants; and the good thing is, the water won’t run out on your barrels. Isn’t that great?