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How Much Rain Can I Collect In a Year?

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How quickly will my rain barrel fill?


This depends on how much rain you get, the size of the roof supplying the rain, plus how large the inflow pipe to your rainbarrel is. Typically, one rain barrel will fill in just minutes in an average downpour.

One inch of rain on a 1000 square foot roof will yield around 600 gallons. So all you need to do is some simple math. Determine the square footage of the area that's connected to your rain barrel and multiply it by 0.6, ( sq. feet x 0.6 = gallons).

ex: 1000 sq' x 0.6 = 600 gallons

How much rain you can collect off your roof is determined by how large your system is and how much rainfall you have in your area. Let's say you have unlimited storage....

ex: If you live in Portland, OR, your average rainfall is 37.07 inches and you have a 1500 square foot roof.

1500 x 0.6 x 37.1 = 33,390 gallons a year.

Average Rainfall for Select Cities

You can find how much rain falls in your area by entering your zip code at Wunderground.com.

Oregon

  • Astoria - 67.1"
  • Bend - 11.7"
  • Burns - 10.6"
  • Eugene - 50.9"
  • Medford - 18.4"
  • Pendleton - 12.8"
  • Portland - 37.1"
  • Salem - 40"

Washington

  • Olympia - 50.8"
  • Quillayute - 101.7"
  • Seattle - 38.3"
  • Spokane - 16.7"
  • Vancouver - 41.3"
  • Walla Walla - 20.9"
  • Yakima - 8.3"

California

  • Bakersfield - 6.5"
  • Eureka - 38.1"
  • Fresno - 11.2"
  • Los Angeles - 15.1"
  • Redding - 33.5"
  • Sacramento - 17.9"
  • San Diego - 10.8"
  • San Francisco - 22.3"
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