Floating ideas on rain barrels

I keep watering a lot because the lettuces growing in our back porch planters are thirsty. That is one of the drawbacks of planters. They don’t have much of a moisture reservoir and need water once, sometimes twice a day.

I was done schepping the watering cans out of the basement and decided that a new set of rain barrels would make my watering chores much easier. Plus they would convert a waste product (roof runoff) into a useful resource (water for irrigation).

Yet the how-to on rain barrels hasn’t quite trickled into our general knowledge base. I constantly run into this when speaking at conferences about rainwater harvesting options. Rain barrels seem so simple, yet it actually require some thought to get them right.

Raison d’être

Harvesting roof runoff and/or mitigating the impact of stormwater runoff is the primary function of rain barrels. That said, they can quickly become a white elephant, unless you plan to actively use them. In other words, you have a need for the harvested water, and/or it is likely that you draw the rain barrels empty on a frequent basis.

Some municipalities have rain barrel programs, which I mostly regard as well intended but not that helpful. The hope is that the rain barrels store some runoff and keep it out of the overtaxed stormwater system. Yet I noticed that most of those rain barrels, once installed, serve as mere decoration, and the stored water is not used or drained. The barrels sit there full with water for most of the warm season, which completely negates any intended runoff mitigation.


Say you have a good use for rain barrels or are willing to drain them between storms. What would be the contributing area (i.e. the size of the roof) that would feed into the rain barrels?

If you have a small bike shed with a couple of 55 gallon rain barrels connected to it, you may have to wait for quite a while before they fill up. Conversely, if you have a couple of rain barrels connected to a 2000 square foot roof, they may fill up in the blink of an eye.


For rain barrels to provide any runoff mitigation benefits, their storage volume should be sized proportionally to the contributing roof area. For example, say they can store a quarter or half inch of rain fall on the contributing roof area. This may be more volume than you need for irrigation. In this case the barrels should be drained prior to approaching storms, to free up the storage volume.


How do you get the water from the gutter and downspout into the rain barrels? These days you can find a variety of downspout diverters that solve that problem for you. The better ones have a built in filter that keeps debris out. The really fancy ones even have a winter bypass.

I used a homemade diverter and filter on our early rain barrels. It was not pretty, ideal or long lasting, but it did the job at the time.


Most rain barrel products come prepared with plumbing connections. But not all of them make sense. Here are some things to look out for:

If more than one barrel is needed, make sure they are connected to each other at the very bottom. You may have several barrels, but this way you have one storage volume. It allows you to access that entire storage volume from any barrel, and it will allow you to drain all barrels at once, which is important for winterizing.


Go with a product that has the faucet to draw water from the barrel at the very bottom, not one third or half way up. If the faucet is not at the very bottom, you never can effectively use all of the stored water, or completely drain the barrels between storms or for winterizing purposes.


Set the rain barrels on a pedestal. This would allow you to fit a watering can or bucket under the faucet, even if it is at the very bottom of the barrel.


Well, this is really part of the plumbing, but it deserves a special mention.

Your rain barrel(s) will be full at some point. If it continues raining, you have to have a plan on how to deal with the overflow. A lot of people don’t and inadvertently create flooding issues where there previously were none.

For a starter, make sure the rain barrels have an overflow pipe somewhere at the top. That overflow pipe should be the same size as the supply pipe that is delivering water into the rain barrels. Under no circumstances should the overflow be smaller than the supply.


Rain barrels are often placed right next to the house – next to a downspout. Have a plan on how to divert the overflow a safe distance away from the house and thus keep your basement foundation dry. A swale, a pipe extension or a channel could do that job.


If you are in a freezing climate, you need to winterize your rain barrels. That means they need to be completely drained during the freezing months. In addition, you have to disconnect the downspout diverter so no water is fed into the rain barrel(s). If you have a fancy diverter, you will need to put it into winter bypass mode, which should keep runoff out of your barrels.

If you fail do any of the above, or miss one of those steps, you are likely to become a proud owner of a giant ice cube … an ice cube that will make your barrels burst or crack.

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About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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