Rainwater can be dangerous when it runs off of impervious surfaces such as parking lots, streets and sidewalks. As it rushes to the nearest storm drain inlet, it will pick up oil, chemicals, sediment, bacteria and other pollutants and eventually carry them into local waterways. In areas where the rivers that capture polluted runoff double as local drinking water sources, this is a serious issue. Some studies have estimated that as much as 70% of the pollution in surface waters is caused by runoff. Capturing as much rainwater as possible during the wet season and saving it for later is one way to circumvent these problems and lower usage.

By some estimates, one inch of rain on a 2,000 sq. ft. roof generates more than 1,000 gallons of water. Just imagine how that water might be applied. Storing rainwater in large tanks and recycling it for use in irrigation systems can make a big impact on outdoor water use. Outdoor water use has been estimated to account for up to 50 to 70% of a household's total usage. As rainwater harvesting takes off, it could present significant opportunities for contractors now and in the near future.

Taking a cue from down under

When it comes to harvesting rainwater as a large-scale solution, Australia is ahead of the curve. This isn't merely an attempt to be cutting edge, however. In Australia, drought is more than just a wait-and-see issue. Down under, drought is a way of life, and the current drought has been called the worst in 1,000 years.

State governments in Australia have met the situation head on and are requiring new homes to be designed and built with the latest energy and water-efficient designs and products. Rebates are offered to homeowners who choose to install water tanks. Consequently, collecting rainwater and storing it for reuse is a common practice. The widespread awareness of conservation is a good model for the U.S.

Here in the U.S., cities such as Portland, Oregon, are meeting water crises in a number of ways. Portland's Downspout Disconnect Program encourages homeowners to disconnect their downspouts from the combined sewer/stormwater system and then use roof runoff to irrigate their landscapes. The city will do the work for free; homeowners who do it themselves can get a $53 reimbursement. More than 42,000 homeowners have participated, removing 942 million gallons of roof water per year from the combined sewer/stormwater system.

Since Leadership in Energy and Environmental Design (LEED) standards were established by the U.S. Green Building Council in 1998, more than 14,000 projects have earned some level of LEED certification. Rainwater harvesting can account for one point. This is part of an overall objective to reduce by 50% the amount of fresh, potable water used for irrigation.

As the conservation movement takes hold in more areas than ever before, there is renewed interest in rainwater harvesting. Rain barrel sales grew this past summer and fall. Local water authorities have begun to promote rainwater harvesting.

There are a number of manufacturers/ distributors of large water tanks and/or rainwater recovery c o m p o - nents that h a v e a range of a p p l i c a - t i o n s , including meeting LEED standards or garnering rebates. This is a field that is more sophisticated than many people realize. Harvesting rainwater in tanks or cisterns provides a high level of protection from contaminants. The clean water can be discharged for irrigation of turf and plants or used to feed water features. And as the harvesting movement takes off, people are discovering a variety of other applications.

Rain, rain-don't go away

Generally there are four components of a rainwater recapture system: capture, conveyance, holding and distribution. As long as you don't plan on using the rainwater for drinking purposes, basically any type of roofing material is acceptable for capture. From the roof, gutters convey the water to downspouts and into the tank. It is advisable to install filters to prevent leaves and debris from blocking gutters. Then, to deflect any other debris and to keep bugs out of the pipes, rain heads can also be fitted to downpipes. Additional filters at tank entry points will provide further protection.

Bushmans, located in Australia and the U.S., is a manufacturer of rainwater recapture tanks. It supplies what it calls "first flush diverters," which as the name sugg e s t s , send the first flow of water from the roof into a separ a t e chamber. This is to prevent the initial, more contaminated flow from going directly into the tank. Tanks are often the most expensive part of a recapture system, but they're specially constructed to withstand corrosion and pressure for many years without leaking or bursting. Most tanks come with overflow outlets to discharge excess water a safe distance from the tank.

The size of the tank needed depends on the amount of rainfall, the roof area and demand, which will vary from property to property. "If the tank will be used in conjunction with an irrigation system, factor in the size of the area and how much water would be needed in the worst-case scenario," says Daniel Benner, founder of Hydro Environmental, Inc., in Marietta, Georgia. Depending on how the harvested water will be used, it may have to carry the tank owner from one rain event to the next. It's important to correctly estimate water usage when determining the size. However, Benner notes, "It does make you use water conservatively."

Smaller tanks for residential use typically fall in the 300-500 gallon range, while larger tanks for commercial use can be several times that size. In general, tanks should be durable, watertight and have a smooth, clean interior. They can be stored either above or below ground. Larger tanks are located below ground, where they will be protected from temperature changes.

Darco, based in Bennett, Colorado, is a manufacturer and distributor of tanks. The company's large underground polyethylene tanks and fiberglass tanks clean water when it enters the first module, called the clarifier module. In this module, a silt dam allows the sediment to settle out of the runoff. Only clean water is allowed to enter the next module.

Above-ground tanks are easier to retrofit to an existing property. Obviously, it's easier to install a tank without having to excavate a large area first. And above-ground installations require less specialized equipment and knowledge. Homeowners who are interested in testing a recapture system may start out with a small aboveground tank. With the variety of color options and slim designs that slide up under the eaves, the tanks don't have to be an eyesore. The color is not purely aesthetic, however. It prevents UV-rays from penetrating the tank and raising the possibility of algae growth. Unlike underground tanks, most of the cleaning is done by the filters before water enters the tank.

Properly maintained systems pose a very low risk of disease. Although microbiological or chemical contaminants in the water do have the potential to exist and cause problems, there is little evidence to suggest that rainwater stored in tanks is unsafe for use. In fact, about 10% of Australians even drink their harvested rainwater, although this has not been endorsed.

An important component of a rainwater recapture system is what Ron Harris, western states sales manager for Darco, calls the "makeup water valve." Most tanks, regardless of manufacturer, come with a similar device that maintains the minimum level of water in the tank. Let's say, for example, that level is 12". If the level of water dips below that mark, the valve, which is hooked up to a potable water system, will release more water to fill the tank. However, all of the available rainwater will be used up first. This is especially helpful for tanks that serve as sources of water for irrigation s y s t e m s because it alleviates the burden on the tank owner to have to keep the tank at an a d e q u a t e level.

To simplify the process of setting up a recapture system, Paul Bassett, founder o f J e s s u p , M a r y l a n d - based Hydro- Logix Solutions, has created rainwater harvesting kits that contain all of the necessary components, including filters, pumps, soil sensors, irrigation controllers and drip emitters. "Rainwater harvesting is a great way to manage an irrigation system," says Drew Zogby of Chanell Commercial Corporation in Temecula, California, which manufactures and distributes Bushmans' tanks in the U.S. market. For this application, an irrigation controller activates a pump in or on a tank. Then the controller will direct the pump to deliver water to an irrigation system for a preset amount of time.

"Additional filtration may be needed," Benner adds, "to catch any other debris or particulate matter." Generally though, the water does not need to be treated before being used for irrigation. As a benefit, the water is often loaded with nitrogen, which fortifies plants and turf and provides color. However, if the water has been sitting for awhile, the nitrogen may have evaporated. If the rain is feeding a water feature, the nitrogen levels could cause harm to fish and plants, so it must be treated as potable water would.

Another benefit to these systems is the generally low maintenance, similar to that of any other irrigation system. Depending on the type of surface that rain runs off of or the type of water being stored, tanks will need to be cleaned anywhere from once per year or once every several years. It is also important to clear out gutters periodically to keep the water that enters the tank as clean as possible. If the tank feeds an irrigation system, the pump will need to be serviced on a yearly basis.

Brian Vinchesi, principal of Irrigation Consulting in Pepperell, Massachusetts, advises contractors who are interested in rainwater recovery systems to "think about it early on in the process. These systems are best for new construction although they can be retrofitted to an existing property. If you are retrofitting a system, make sure you will be able to collect a sufficient amount of rainwater."

As this field continues to grow, people will find additional uses for harvested rainwater that could change the scope of water usage. Bassett encourages contractors who are interested in rainwater harvesting to contact their local chapter of the U.S. Green Building Council and join the EPA's WaterSense program. Once they do so, this can be a great revenue generator. "Harvesting rainwater and using gray water are the next big things," Vinchesi believes. It's timely, yes. But more importantly, it's responsible. And if you're looking for a way to practice sustainability without sacrificing your business, the time is ripe with opportunity.