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www.greenbuildermag.com 08.2012


~ How-to ~ 18


BUILD AN EXPANDABLE RAINWATER SYSTEM


This ultra-low-budget rainwater system can be upgraded later. Better yet, it’s made from mostly salvaged materials.


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ROUGHLY SPEAKING, THE formula for how much rain a roof can collect is collectable rainwater (gallons) = 0.5 x rainfall (inches) x area (square feet). The amount of potential water collected varies by geography, but in a


typical year, a house in an eastern state might collect 15-25 gallons per sq. ft. annually. That would add up to 1,500 gallons or more for even a small home. Irrigating drought-tolerant shrubs and gardens requires at least .3 gallons/week per sq. ft., according to www.conservationtechnology.com. So if you have 500 sq. ft. of dry climate shrubs, and you live in the Northeast, you’ll collect enough water for 10 weeks of watering. The system shown has only 100 galons storage capacity, but it’s expandable, and over time, the 50-gallon tanks could easily be replaced with a full- sized cistern. This article is meant as a general guideline—not a blueprint. The author says he continues to tweak and change details, so make your own adjustments. The general concepts and materials it demonstrates, however, remain the same.


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The fi nished system consists of two barrels that are gravity-fed from gutters and “share” a single rain input. Almost any type of surplus plastic barrel can be used. We have not


supplied a materials list, because the author says there are much more durable screw-together alternatives for many of these plastic fi ttings, available at any hardware store.


Drill and insert pipes. In this early prototype, the author simply caulked the fi tting into the hole, but he suggests that a threaded PVC fi tting with internal “nut” would make this detail neater and stronger.


Split the proceeds. A PVC “T” assembly divides water from the barrels and sends it to a single 3/4” pipe for fi nal delivery.


Drill and connect tubing. The 5/8” clear tubing at mid-height between barrels balances volume, at the same time letting you know when half the reservoir is gone.


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