What you should know about rain barrels and water conservation if you live in the Portland metro area
It’s true that it rains a lot in the Pacific Northwest. But, unlike other parts of the country that receive rainfall year-round, here in the Portland metro area we typically receive the least amount of rainfall during the summer months – a time of year when our outdoor water usage is at its highest.
The Portland metro area gets about 37 inches of rainfall annually and typically we receive about 90% of that rainfall from October to May – a time of year when we don’t need extra water to irrigate our gardens or lawns. Because of this seasonal rainfall pattern, and their limited storage capacity, rain barrels are not the most effective water conservation method for our region.
A typical rain barrel holds about 55 gallons. This may initially seem like a lot of water, but take a moment to consider your landscape’s water needs and you may find that it will take far more rain barrels to water your landscape than you initially thought.
We recommend watering an established lawn about 1 inch of water each week (a bit more in hot, dry weather). So, if you have a 100 square foot patch of lawn you will need about 62 gallons a week to water the recommended 1 inch. Assuming you will water this grass from May-September, you will need to collect at least 1300 gallons of water. That translates to about 24 rain barrels!
And, while this seems like a lot of water, it may actually only be a fraction of the water that will run off your roof and through your downspouts in a typical year.
For example, a roof with a 1000 square foot area will yield about 620 gallons of water in a 1 inch rain event – enough to fill a 55 gallon rain barrel 11 times. Considering our annual rainfall, that roof could yield more than 417 rain barrels each year!
So, now what?
If your original goal for installing a rain barrel or two was to conserve water, don’t despair! Though rain barrels are not the most effective conservation method – they will help save some water.
We also recommend checking out some more effective water conservation alternatives such as installing sprinkler controllers and rain sensors, or using a hose with a shut-off nozzle. You can find out about these and other water conservation tips under the outdoor and indoor sections of this website.
Rain Barrel FAQs
What is a rain barrel?
Rain barrels are containers that divert and collect rain water that otherwise would flow off a roof, through gutters and downspouts and become runoff. Water captured in rain barrels is typically used for outdoor irrigation purposes.
Rain barrels come in a wide variety of materials (plastic and wood are the most common), designs, and colors. Common sizes for residential use are 55 to 90 gallons. Prices range from about $50 for do-it-yourself kits and up to several hundred dollars for ready-made rain barrels. A quick Internet search of “rain barrels” will bring up numerous informative sites and retailers. We have also developed resources section on the back of this brochure to get you started.
Will I save money on water by installing a rain barrel?
In short, no. Here in the greater Portland metro area we are fortunate to have relatively inexpensive water. (Check your water bill for actual cost. Many providers combine water and sewer costs on the same bill, so be sure you are looking at the water section only.)
Once you know the cost of your water you can figure out how long it will take you to recoup the cost of the rain barrel.
For example, let’s say you have a 55 gallon rain barrel that cost you $90. If your water provider charges $1.97 per CCF,* you would save an average of $.14 each time the rain barrel filled. Using this example, you would have to fill the rain barrel 643 times just to break even on the cost of the barrel. At a rate of emptying and filling the barrel 50 times a year – it would take almost 13 years to make your money back! (*Most water providers measure water in CCF. One CCF represents 100 cubic feet or 748 gallons of water. Check your bill for the rate your provider charges per CCF.)
Beyond the initial cost for the rain barrel, there are additional maintenance costs that should be considered.
Where can collected rain water be used?
Collected rain water is commonly used for exterior, non-potable purposes, such as irrigation. Typically no permit is required for irrigation use; however, be sure to check local codes and ordinances on the use of rain barrels before you do any disconnections or alterations to your property. There are differing opinions about using water from a rain barrel on edible plants such as vegetables, fruits or herbs. Be sure to do some research to determine what option is right for you.
What should I do with the rainwater I can’t collect?
A typical 55-gallon rain barrel will capture only a fraction of roof runoff, so be sure to include an option for overflow into your plan. Some rain barrels are set up to divert excess water into another rain barrel or back into the storm drain once they are full. Another option is to send your overflow into your yard making sure that it drains away from your foundation to a safe discharge location. Rain gardens are also becoming a popular way to incorporate rainwater runoff into your landscape (See the resources section on the back of this brochure for more info).
City of Portland Bureau of Environmental Services Stormwater Management How To - Rain Barrels
2015 Sightline article: A Green Light for Using Rain Barrel Water on Garden Edibles