Green Building & Rainwater Collection

Rainwater systems keep a valuable asset from going down the drain

One aspect of climate change is a change in attitude about natural resources that are taken for granted. Take water, for example. Drought-stricken areas of the country enacted water restrictions and even those areas not as hard hit witnessed rivers and lakes receding to alarming low levels. Homeowners notice higher water bill, rethink landscaping plans and wonder how to accommodate the changing environmental conditions.

Rainwater systems offer low-maintenance solutions for rainwater collection, filtration, storage, and re-use. Typically, water from all of the downspouts of a building is piped to a central underground filter that separates solids. The filtered water is stored in underground storage tanks ranging from a few hundred gallons to many thousand gallons. Specialized pumps, control systems, and disinfection systems draw water from the storage tanks for irrigating landscapes, filling swimming pools or ponds, flushing toilets, and washing clothes. Not only is it good for the environment-it’s good for the wallet, to. Although initial equipment installation can be significant, long-term costs are minimal.

Rainwater is an economical alternative to public water, especially for exterior water uses like watering the law. Because it is low in minerals, it is ideal for laundry, dishwashing, hair and car washing. Because it contains no chlorine, rainwater is also ideal for filling garden ponds. During periods of drought, rainwater can protect investments in landscaping, garden ponds and swimming pools.

On average, Americans use 70 gallons per person per day to operate toilets, showers, clotheswashers, sinks and other water-using fixtures and appliances. By replacing fixtures and appliances with modern water-efficient versions and repairing leaks, water usage can be reduced to less than 50 gallons per person per day. Since these simple conservation measures require no behavioral changes and are less expensive than providing additional rainwater storage capacity, any rainwater utilization system should presume water conservation.

A family of four will require 50 x 4 persons x 30 days = 6,000 gallons per month for all interior water consumption (toilets, clotheswasher, showers, sinks, other) or (10 + 10) x 4 persons x 30 days = 2,400 gallons per month solely to flush toilets and wash clothes.

Water used irrigate landscaping often equals or exceeds interior water use. Water required for this can be greatly reduced by selecting native plants, or plants that thrive in regions with similar climates so that irrigation Is only needed to compensate for natural variations in rainfall. Filling and topping swimming pools is another significant water use.

Rainwater Storage Tanks

Above-ground rain barrels and storage tanks offer a simple and inexpensive way to collect rainwater from a single downspout for landscape watering. Underground tanks are more suited to whole-house rainwater collection systems, but considerably more expensive to purchase and install. Underground tanks are invisible, are unaffected by freezing weather and can last indefinitely.

Rainwater Filters

Rainwater collected from rooftops contains significant quantities of plant debris, dirt eroded roof materials, and other solids that can clog pumps, valves and pipes. Mineral solids collect as sediment at the bottom of storage tnaks, reducing tank storage capacity; organic solids decompose, depleting oxygen and generating hydrogen sulfide and other noxious by-products. One way to improve the quality of rainwater is to intall a "roof washer," a devise that discards the initial runoff from a roof before it reaches the storage tank. A more efficient solution, however, is provided by a new generation of low-maintenance rainwater filters that capture all solids larger than 500 microns (1/50"). This level of filtration is sufficient for exterior water use such as watering lawns or gardens and filling pools and ponds. For interior water use, supplemental filtration and disinfection are essential.

Pumps and Controls

When water stored in above-ground tanks is to be used for low-pressure irrigation, a simple gravily-flow system may suffice to distribute the water.

In all other cases, an oil-free submersible or external pump is required.

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Information from Resource Conservation Technology, Inc., Baltimore, MD, www.conservationtechnology.com