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As right as rain: 6 things you must know before harvesting rain

Matthew Grocoff

July 10, 2015

By: Matthew Grocoff, Green Renovation Expert

In: Roofing and GuttersGreen LivingPlumbing

"As natural as rain" is the expression of purity. Yet once rain hits our rooftops we call it "stormwater" and it costs cities billions to deal with. In many cases, stormwater from all of our roofs, roads, driveways, and parking lots collects so violently and rapidly that it causes sewage treatment plants to overflow. Often, the plants must discharge raw sewage into our natural waterways. When that pure rainwater connects with our paved surfaces, it becomes pollution that we must control.

What if the falling rain actually provided a benefit to the property on which it landed? What if we could water our lawns with, wash our clothes with, or even drink the rain?

Rainwater harvesting is becoming widely accepted in cities around the country as an immediate means to mitigate droughts. Cities like Atlanta, Georgia have adopted progressive new laws that allow homeowners to capture, store, and treat water for many purposes inside the home.

If you're considering harvesting your rain, here are a few things you should think about before you get started. It's not as simple as sticking a rain barrel under your drain pipe. But when done correctly, you'll find that your rain can have a net positive impact on your family, your home, and your community.

1. Catchment Surface

The first stage of any rainwater harvest system begins with the catchment surface. Typically, that's the roof of our house, shed, porch, or other structure that first comes in contact with the rain. This is a vital but often overlooked part of rainwater capture. In our home, a team of University of Michigan College of Engineering Students found high levels of lead in our asphalt roof shingles. We replaced our asphalt roof with a stamped metal roof from Matterhorn Roofing. (Read more here). Metal roofs are becoming the most popular surfaces for harvesting rain. Be wary of painted or colored roofs. A good choice for rainwater collection is a clear Galvalume coating. Galvalume comes with a Declare Label which ensures that there are no Red List Chemicals of concern in the product.

2. Gutters

Once the rain lands on the roof, it heads to the gutters. Again, gutters are often overlooked. Good gutters are worth every penny. Our original gutters were undersized and flimsy. When it rained or snowed the gutters bowed, bent, and shed water over the edge, defeating the purpose of having gutters. We replaced our cheap gutters with a 6" Galvalume half round gutter.

3. Flush and/or filter (optional)

Before sending the rainwater to your storage container it should pass through some type of pre-filter system. A simple solution is the first flush diverter. Dave Stark from Stark Rainwater Harvesting recommends WISY pre-tank filters for larger systems. This will help clean out leaves, dirt and debris and keep the tank from needing to be cleaned more than necessary.

4. Storage

The simplest systems for storage are rain barrels. I feel that rain barrels are like the Arkansas Traveler who asks the farmer "Hey, Farmer. Why don't you fix that leaky roof?" The farmer answers, "Well, when it's raining it's too wet to work and when it's dry it's just as good as any man's roof." Rain barrels tend to overflow when it rains and are dry during droughts. A 1,000 square foot roof can harvest 600 gallons of water in a 1 inch rainfall. If you have a 50 gallon ruinable, it will overflow with less than an inch of rain. During a drought, 50 gallons won't be enough to water your vegetable garden for more than a day or so.

For medium systems, one good solution is the Rainwater Pillow which is portable and can fit under a deck. For bigger systems you'll want to consider a larger above or below ground storage tank. Here's a few examples from Rainwater Management Company

5. Overflow

Overflow is essential in any system, even a small rain barrel. If the storage system overflows, the water must be diverted to a place where it can safely infiltrate back into the ground. It's a good idea to direct overflow devices into a nearby rain garden.

6. Distribution

From here you can go in two directions: potable or non-potable usages (i.e. will the water be used for drinking). If the water is not used for drinking it is called non-potable water. In most jurisdictions, non-potable water is allowed for use in landscaping. In some jurisdictions, code allows for use of rainwater inside the home for things like toilets and washing machines or any fixture where your mouth will not be in contact with the water. Curiously, some cities require signs above the toilet that say "Not for Drinking."

When the water is intended for drinking, regulations can get pretty strict. Potable, or drinkable, water must pass through a filter system which typically ends with a UV light treatment to ensure that all pathogens are eliminated. If that's the route you want to go, here's a great site to explore.

With all these options, collecting rainwater is down to a science. You can get started today.

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