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These two, 2,800-gallon polyethylene storage tanks can provide about a three months' supply of rainwater for a water-conserving household of two.

These two, 2,800-gallon polyethylene storage tanks can provide about a three months' supply of rainwater for a water-conserving household of two.

Rainwater catchment is a simple and cost-effective practice that we all can do, whether it's small scale, providing water for a few tomato plants—or large scale, supplying all of a household's needs.

As the world's population continues to grow, so has our appetite for resources, especially water. All over the world, groundwater levels are falling as water is pumped out and consumed faster than it is naturally replenished. Everyday human activities—such as sewage disposal— as well as heavy industry and agriculture, continue to pollute and deplete groundwater sources. To add injury to insult, in the United States more than 50 percent of the wetlands that recharge and purify groundwater have been destroyed. On islands and in nearshore regions, pumping too much water from wells can result in saltwater intrusion into aquifers, rendering the water unfit for drinking or irrigation. Once saltwater is drawn into a well, freshwater will not likely ever replace it; in many cases, the well must be abandoned.

Collecting and using rainwater can help protect aquifers and groundwater tables, as well as offer better quality water for drinking, cooking, bathing, washing, and irrigation. Because it's captured before it hits the ground, rainwater is far less contaminated than most surface and underground water supplies.

Rainwater, being naturally distilled, does not have the minerals that groundwater contains, making it ideal for showering and clothes washing. Rainwater lathers and rinses better than most groundwater, and clothes washed with rainwater are often softer.

Having a barrelful of rainwater can tide you through an emergency, such as a power outage or if your well pump fails. And having a tank of rainwater handy could save precious fruit trees or vegetables during a drought, when restrictions are placed on municipal water use.

After the initial investment of storage and filtration equipment, harvested rainwater is free, which may be one of the best reasons to invest in a catchment system.

Catch & Store

The best surfaces for catching rainwater are smooth, enameled metal or tile roofs. All roofs should be tested for lead and other contaminants if the rainwater is intended for potable use or for watering edible plants. Asphaltshingled roofs are not recommended because they may shed unwanted compounds into the water. Cedar shake roofs will catch more dirt and leaves, which may end up in the water, and may also impart a yellowish color to the water due to tannins leached from the wood. This yellowish color stains clothing and fixtures, and can reduce the transmittance of ultraviolet (UV) light and may diminish the effectiveness of a UV-light treatment system used to purify rainwater for drinking. Avoid harvesting rainwater off of treated wood-shingle roofs, which may leach toxic chemicals into the water. To be safe, always test your harvested rainwater before using it in your home or garden.

A rainwater storage system can be as basic as an old, watertight whiskey barrel or 55-gallon (208 l) plastic drum. Folks with greater rainwater aspirations may choose to use large polyethylene ("poly"), potable water, FDA approved, tanks, which are lightweight and relatively low cost. These tanks come in a range of sizes, the most cost effective being the 2,500- or 2,800-gallon (9,463 or 10,599 l) size. Poly tanks also come in larger sizes (5,000 and 10,000 gallons; 18,927 and 37,854 l), but shipping costs often outweigh the cost savings in purchasing a large tank. Some states

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The basic components of a rainwater irrigation system, including pump and pressure tank, in an insulated box.

What's Your Roof's Rainwater Potential?

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To calculate your roof's rainwater potential in gallons per inch of rainfall, multiply 0.6 times the square footage of your roof. Be sure to calculate the roof area by the roof's footprint, rather than by the roof's surface area. (For the same-sized home, an A-frame-style roof has more square feet of roofing, but has the same amount of rainwatercollection capability as a flat roof.)

For example, 1 inch (2.5 cm) of rain on 1,000 square feet (92.9 m2) of roofing area will yield 600 gallons (2,271 I) of water. I live in an area that receives between 18 and 25 inches (45.7-63.5 cm) of rain per year. I usually estimate the rainfall at 20 inches (50.8 cm) per year. Using this figure, a roof area of 2,000 square feet (185.8 m2) will yield about 24,000 gallons (90,850 I) of water annually. This roof area will capture almost enough water to supply a water-conserving household of two using 35 gallons (132 I) per person, per day.

Rain Catchment Area:

Footprint of rainwater collector

Rainwater Harvesting System Components

Pressure Tank:

Maintains operation pressure, allowing pump to run intermittently

Rain Catchment Area:

Footprint of rainwater collector

Pressure Tank:

Maintains operation pressure, allowing pump to run intermittently

Water Treatment:

May include filters,

UV light, and/or chemical additives

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Roof Wash System:

Diverts first few gallons of rainfall and traps ' debris; can be manual or automatic

To House

Water Treatment:

May include filters,

UV light, and/or chemical additives

Roof Wash System:

Diverts first few gallons of rainfall and traps ' debris; can be manual or automatic

To House require a building permit for tanks with more than a 5,000-gallon capacity. Instead, smaller polyethylene tanks can be plumbed together to increase storage capacity. (Note: Do not use tanks designed for septic systems for rainwater storage.)

Larger tanks made of wood, concrete, ferro-cement, fiberglass, steel, or steel with a liner can be used to hold greater volumes of water. Whatever type of storage tank is selected, well-designed systems include an overflow pipe that is directed away from the base of the tank to prevent excess water from washing out the tank's foundation.

The simplest systems place barrels or tanks directly under a downspout. Another option is to route multiple downspouts to a small catchment basin and pump the water to a tank or tanks located away from the house. On properties with varied topography, tanks may be placed on high ground, enabling gravity flow back to the point of use. Every 2.3 feet (0.7 m) of elevation or head produces 1 pound (0.45 kg) of pressure. This means that a head of 23 feet (7 m) will produce a gravity flow of 10 pounds (4.5 kg) of pressure— enough for faucets, but not enough to push the water through most filters. Most rainwater harvesting systems will need a pump and a pressure tank, since the vertical distance between the tank and the point of use usually is not great enough to provide adequate pressure for normal household use.

Filter First

The more organic matter you can prevent from entering the storage tank, the better your water quality will be. Even if you just want to use the water for irrigation, having a filtration system to remove large leaves and other debris helps prevent pipes and fittings from clogging.

Gutter screens, downspout traps, or strainers in the top of the tank can all be used to filter out coarse debris. Screens on the gutter are the first line of defense, and are simple

In this multiresidence, potable water system, rainwater first passes from the pump to a pressure tank, and then is routed through a sediment filter, two carbon block filters, and a UV-light purifier before being distributed.

In this multiresidence, potable water system, rainwater first passes from the pump to a pressure tank, and then is routed through a sediment filter, two carbon block filters, and a UV-light purifier before being distributed.

Homemade Irrigation Strainers

and inexpensive to install. A manufactured downspout clean-out, which replaces a section of downspout with a screened catch, also works well. A larger basket-strainer of 20 mm (0.79 in.) mesh, which fits inside a barrel or polyethylene tank, also is effective. For best results, use all three methods.

Roof washers collect and discard the first few gallons of water that wash from the roof, and protect your storage tank from debris that slips through the screens. Several types are available, ranging in price from US$100 to about US$600. One simple roof washer consists of a small reservoir, which fills with the first batch of roof water. After it fills, a floating ball plugs the reservoir's opening and water is diverted to the storage tank. A small hole in the bottom of the reservoir allows the water to slowly drain and readies the roof washer for the next rainfall. Other roof washers combine filtration and pumping in one unit. Although roof washers remove some debris, washers can never completely remove all of them. All require regular maintenance to prevent clogging.

Rainwater Uses

Water used for irrigation can be pumped directly out of the storage tank. If you are using drip irrigation or soaker hoses, consider filtering the water after the pressure pump. Most drip systems function best with 10- or 20-micron filtration.

Rainwater destined for potable use requires both filtration and treatment to remove bacteria and viruses. Three common methods of treatment are chlorination, ozonation, or UV-light treatment. For a whole-house water purification system, UV-light units typically are the most trouble-free and easiest to maintain.

When rainwater systems are the only source of water for a whole-house water system, local health departments usually require that the storage capacity must maintain the household for a period of three months without any recharge of the storage tanks. On a backup system, this requirement is not usually enforced. In Washington State, San Juan and Jefferson counties have approved building permits with rainwater catchment systems based on a usage of 35 gallons (132 l) per person per day. (The average American uses about 100 gallons; 378 l of water per day.) This requires using water-saving appliances like low-flow showerheads, low-flush toilets, and horizontal-axis clothes washers. Minimal or no outside watering is allowable if the rain catchment storage capacity is close to the minimum yearly usage calculated.

The best time to plan for rainwater catchment and use is during the design phase of your home. Rainwater can be used with minimal filtration for flushing toilets. And, in some areas, rainwater is permitted for use in showers or for laundry. It is important to understand your local regulations when designing and building a system. If you are retrofitting rainwater catchment to an existing system or using it to supplement an existing potable water supply, such as a community or municipal water system or well, be sure to install an approved backflow preventer between the existing system and the rainwater system.

Roof Catchment Water Supply Design
This 27-foot-diameter, 14-foot-tall, steel storage tank, lined with an FDA-approved PVC liner, can store about 58,000 gallons of rainwater.

Many states, as well as municipalities, have regulations governing rainwater catchment. A few states require a water right for large-scale rainwater catchment systems. Check with your local agencies to determine the level of control on rain catchment in your area.

Costs

A small rain barrel to put under a gutter can cost as little as US$25. Larger polyethylene tanks, which hold more roof runoff, cost from US$950 for a 1,500-gallon (5,678 l) tank to US$1,200 for a 2,800-gallon tank. The 2,800-gallon size is the largest polyethylene tank that can be easily transported, and it is also the best value for your dollar. Larger steel tanks with liners cost from US$0.35 to US$0.65 per gallon of storage capacity. In addition to storage tanks, a whole-house rainwater catchment system with a booster pump, filters, and UV-light treatment can cost a few thousand dollars.

Rainwater harvesting systems are most economical in areas where the water supply is expensive, unreliable, or of questionable quality; in drought-prone climates; or in places lacking access to a municipal water supply. But whatever your situation or size of your wallet, a rainwater harvesting system can be installed almost anywhere for a cheaper and cleaner water supply.

Access

Michael Durland, PurRain Watertanks, 155 Channel Rd., Deer Harbor, WA 98243 • Phone/Fax: 360-376-2552 • [email protected]www.purrain.com

Rainwater Collection for the Mechanically Challenged, by Suzy Banks & Richard Heinichen, Paperback, 108 pages, ISBN 0966417062, US$19.95 from Tank Town, 2770 Hwy. 290 W, Dripping Springs, TX 78620 • 512-894-0861 •

Fax: 512-858-2321 • [email protected]www.rainwatercollection.com

Texas Guide to Rainwater Harvesting, Second Edition, by the Texas Water Development Board • Download at: www.twdb.state.tx.us/assistance/conservation/ Alternative_Technologies/Rainwater_Harvesting/Rain.asp

NSF International, 789 N. Dixboro Rd., PO Box 130140, Ann Arbor, MI 48113 • 800-NSF-8010 or 734-769-8010 • Fax: 734-769-0109 • [email protected]www.nsf.org • NSF-approved components for rainwater harvesting systems

Weatherbase • [email protected]www.weatherbase.com • Online database of monthly weather records & averages for more than 16,000 cities worldwide

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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  • Dafne
    How to install pressure tank for well system?
    8 years ago

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