Water Supply From The Sky

[Writer’s note: this is an article I wrote last year but was never published. I wanted to share it with my loyal readers. I hope you enjoy. Rainwater harvesting is fascinating and can be utilized anywhere there is precipitation i.e. everywhere on the planet.]

Living with the convenience of “city” water for over thirty years I was a bit apprehensive when my wife and I bought a little piece of rural paradise upon which to build our new family home. As far as I knew there was only one option for our water supply: a well, drilled deep into the ground pulling up water from the earth. As far as I knew a well meant smelly, slimy, water and iron stained plumbing fixtures. I was not looking forward to a lifetime of well water, but the land was so nice I was willing to sacrifice.

We soon discovered that the area of our new land was not a great place to get a reliable water supply from the earth.  So we had to find another source. The only other real option was to get a cistern, which is a large waterproof vault that holds water. Cisterns have been providing safe drinking water to humans for thousands of years. I immediately liked the idea because it meant no sulfur smelling water or toilet rings.

There are three ways to fill a cistern. We could pay a water hauling company to truck in water. Another option is to use the cistern in tandem with a well, the idea being that the cistern would keep ample water available from even a slow producing replenishment well. Lastly the cistern can be filled with free harvested rainwater from the sky. We wanted our new home to be as environmentally sustainable as possible so we decided to go with harvesting.

With the collection decision made, I needed to do some research.  Foremost I needed to know how much water we’d use and therefore need to collect. The U.S. EPA website estimates about 300 gallons per day per family[1] (109,500 gallons per year). Our goal was to solely rely on rainwater as our supply. If we hit a drought (in the heat of summer or the freeze of winter) we could have water trucked in. We selected a 10,000-gallon underground cistern, which meant we could go a month without refilling it. A low level light comes on at 2,500.

I found the Texas Manual on Rainwater Harvesting[2] online and it is filled with a wealth of information. The manual estimates that one can expect to collect 0.62 gallons per square foot of collection surface, per inch of rainfall. The efficiency of the system is about 75% because some water will be lost in the collection process.[3] So for our example, we have about 4,000 sq. feet of roof to collect water from. Our average precipitation (in nearby Akron, Ohio) is around 40 inches per year[4]…. (4,000 x 40 x 0.62) x 0.75 = 74,400 gallons per year we’ll collect. That’s far from the amount we need but that didn’t deter us from our goal of water independence. Our system cost $14,000 installed.

When collecting rainwater for home use, one has to consider the entire system from raindrop to faucet.  The biggest question mark during the design phase was the roof material. Aesthetically we wanted a metal roof, but weren’t sure if we could afford one. Would asphalt shingles be safe for our water supply? The Texas manual recommends metal roofs, sold under the Galvalume trade name for example, are the best for collecting rainwater for potable use. Potable water should not be collected from wood or asphalt roofs as chemicals can leach from them material into the water. Clay and concrete tiles are okay, but there rough porous surface means a less efficient system.[5] Ultimately we stretched the budget and went with the metal roof.

The collection process is fairly straightforward. As rain hits the roof it flows to the gutters, which have a screen on them to keep large debris out. Water is then directed by downspouts and pipes to roof washers located atop the underground cistern. The washers contain mesh and fabric filters to screen out any large contaminants before the water is deposited into the cistern.  As needed the water is pumped from the cistern into the house where it passes through chlorine and pressure tanks. Lastly the water flows through a 1-micron cartridge filter system to take the chlorine out as well as a final step in the purification process.  The filter’s cost about $30 and we change them six times per year.

WSFTS-Schematic

To minimize water usage we installed plumbing fixtures that use less water. Outside we irrigate the gardens using water collected from a rain barrel. Landscaping with native plants that don’t require supplemental watering helps also. Last year our area saw 33 inches of precipitation through November[6], which is well below average. That being said, our low water light never came on once since we’ve been here. Smaller (and larger) cisterns are available, but we’ve been very happy with the size of our tank.

It was amazing to take my first shower in the new house and realize that the water that was raining around me had fallen from the sky earlier that day. We’ve been very pleased with the system overall and recommend anyone interested in a self-sustaining alternative, look into rainwater harvesting. It’s a viable water source wherever you live.

-Chris

Rainwater harvesting mechanics inside the home include chlorine and pressure tanks, a changeable cartridge filter and low level indicator light.

Rainwater harvesting mechanics inside the home include chlorine and pressure tanks, a changeable cartridge filter and low level indicator light.

On the outside, a rainwater-harvesting house looks like any other except for the exposed cistern lid and roof washers. In this example they are hidden amongst the landscaping in the foreground.

On the outside, a rainwater-harvesting house looks like any other except for the exposed cistern lid and roof washers. In this example they are hidden amongst the landscaping in the foreground.


[2] Texas Manual on Rainwater Harvesting, Texas Water Development Board, Third Edition 2005, http://www.twdb.state.tx.us/publications/reports/rainwaterharvestingmanual_3rdedition.pdf

[3] Texas Manual on Rainwater Harvesting, pp29-30

[4] The Weather Channel website www.weather.com

[5] Texas Manual on Rainwater Harvesting, p6

[6] National Weather Service Forecast Office, Cleveland, OH, http://www.nws.noaa.gov/climate/xmacis.php?wfo=cle

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