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Sunday, June 30, 2013

Harvesting Rain: Rain Barrels, Cisterns and Storage

A rain barrel stores some of the roof runoff at Mother Nature's Backyard

This is the last in our series on ‘Harvesting Rainwater’, which covers harvesting water from the roof (and other impermeable surfaces) and rainwater infiltration techniques. While aimed primarily at gardeners from dry climates, the ideas in this series may be useful to others (see postings from January through June, 2013).

Storing rainwater is an old idea that’s regaining popularity as precipitation becomes less predictable.  The concept is simple: rainwater is stored in a holding tank until it’s needed.  In some parts of the world, rainwater collected in large underground cisterns provides water for much of the year.   A number of U.S. counties and municipalities are advocating a less ambitious goal; the small-scale storage of rainwater for use in home gardens. 

The idea of storing rainwater may not appeal to all, particularly those gardeners living in urban or suburban areas.   Saving rainwater requires purchasing/constructing tanks or barrels to hold the water, connecting these to the water source and then maintaining the barrels/tanks.  All this takes a little time, money and effort.  And unless you use large cisterns – or get rain throughout the year -  you can’t store enough water to make a dent in your water bill.   Small-scale water storage is not going to save lots of money, particularly if you live in a dry climate with seasonal rainfall.

On the other hand, any water saved is useful water.  Stored rainwater is great for watering sensitive plants (including container and house plants) and for crafts like natural dyeing.   Once you have a rain barrel or cistern in place, collection and use is fairly easy.     So you may want to consider saving rainwater in conjunction with the other water management strategies discussed in the past few months (‘Harvesting Rainwater’ series: January to June, 2013).

A rain barrel/tank is generally fed by a downspout from a section of roof gutter. If you haven’t read our post on ‘Harvesting Rainwater: Gutters, Downspouts and Rain Chains’ (February 2013) you might want to do so.   Even in dry climates, the roof collects a lot of water. A general rule of thumb is: for every inch of rain that falls on 1000 square feet of catchment area, a little over 450 gallons of water will be collected. This amount takes into account loss due to friction, evaporation and spillage.  If you only intend to fill a single barrel, that can be accomplished with as little as one-tenth of an inch of rain.

Water from roof gutters is directed to the rain barrel.  Overflow
drains directly into the dry swale ('French drain') 

You can purchase rain barrels and collection cisterns at many hardware, home improvement and garden stores. They are also available through internet retailers, but beware of shipping costs.    The most common sizes are 35-40 gallon and 50-60 gallon, although other sizes are available.  Most are made of plastic (some of recycled plastic) and they come in an increasing range of colors, sizes and shapes.  Prices for a 50-gallon barrel range from $80 to over $200 (U.S. dollars).  Some kits include the needed hardware (or are pre-assembled); others require you to purchase a separate hardware kit.  We suggest you read the resources at the end of this posting before considering your options.

When shopping for a rain barrel, some features to look for include: a spigot that can be connected to a garden hose; a fully screened intake to keep out mosquitoes and debris; a linking system to connect additional barrels; and a sufficiently large overflow hose so that excess rainwater can be carried away. A rain barrel should  allow the user to customize it for their specific needs and should work dependably.

Thrifty homeowners may want to construct their own rain barrel from a recycled food barrel or a sturdy plastic trash can.  Many good resources on constructing rain barrels are available on the internet.   We found these to be particularly good:

Rainwater storage requires a few additional considerations.  First, a filled rain barrel is heavy (up to 400 lbs); it needs a firm, level foundation and should be tied to a wall or post to prevent tipping.  See the resources below for more on this topic.  Second, untreated stored garden rainwater should not used for drinking.  Many municipalities require rain barrels to be labeled: ‘Do Not Drink – Untreated Rainwater’. 

Be sure to check local regulations before purchasing or installing a rain barrel or cistern.  Many municipalities allow homeowners to store rainwater in small rain barrels without a permit; larger cisterns require a building permit in most areas. Los Angeles County has a 4-tier system that covers everything from small-scale rain barrels (Tier 1) to larger storage facilities.  To learn about Los Angeles County regulations see:


Water conservation must become a way of life as our climate changes.  Along with rainwater infiltration, rainwater storage can play a role in maximizing our scarce water resources.  Excellent internet and print resources are available, covering all aspects of rainwater storage - many specifically written for the homeowner.  We suggest you read more before deciding whether rainwater collection is for you.

Good resources for homeowners

More detailed resources on saving rainwater



We welcome your comments (below).  You can also e-mail your questions to: mothernaturesbackyard10@gmail.com 


We welcome your comments (below).  You can also e-mail your questions to: mothernaturesbackyard10@gmail.com 




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