Cisterns and Rain Barrels
A Rainwater-Collection System Saves Water for Dry Spells
Using a free resource
Cisterns and rain barrels collect water from the roof and store it for later use. A barrel may be enough for just a small garden, but more elaborate filter and storage systems can provide all the water a family uses. Cisterns can be anything from an old whiskey barrel to an underground concrete tank big enough to store thousands of gallons of water.
See below for:
PUTTING A SYSTEM TOGETHER
Getting the junk out of water before storage
Bulk storage of rainwater is a tantalizing idea in areas of the country where groundwater is in short supply. With a large enough cistern, a family could draw on reserves for many months—providing that the water is clean enough.
Commercially available roof washers prevent dirt, leaves and other debris from being swept off the roof and into the cistern. Some washers divert the initial runoff completely before rainwater is allowed into the tank; others use filters. Washing off the roof before rain starts also helps keep water cleaner.
One company that makes roof washers is the Water Filtration Co..
When water is pumped from the storage tank to the house for use, sediment and UV filters are used for final conditioning.
Rainfall patterns are a key consideration
The economics of rainwater catchment have everything to do with climate and storage capacity. If it rains periodically throughout the year, with dry spells in between, you probably won’t need a very large storage tank to see real benefits. On the other hand, if you’re in the western part of the country and get all your rain in just a four-month period, you may want to store much more water for use throughout the dry season.
Because storage tanks and related plumbing can be expensive, deciding whether this is a good investment is very project specific. For more information on rainwater collection, visit Toolbase.
Water collection systems can be assembled from simple components
There are a number of parts that go into a rainwater harvesting system, but construction is fairly straightforward, and the general components are available from a number of commercial suppliers.
Judging from this account by an Oregon homeowner, the project is entirely feasible for a motivated homeowner. There is regular maintenance involved, however—filters and other parts need to be changed or checked periodically.
The IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code. has little to say about rainwater collection systems, but local code will likely require that all pipes, fittings, and collection vessels be installed according to manufacturers' instructions (section 2608.2) and comply with IRC section 2608.3, which ensures the components meet National Sanitary Foundation standards.
ABOUT CISTERNS AND RAIN BARRELS
Where water is scarce, save the rain
In drought-prone regions, a rainwater-collection system can help stretch scarce water supplies. At its most elaborate, rainwater collection can provide all the water a household uses with no need for backup supplies.
Big rainwater collection systems are expensive. But in a few locations in the American West where competition for water is already fierce, they may be a cost-effective way to furnish domestic water supplies.
MORE ABOUT CISTERNS
A rainwater collection system designed to supply most of a home's needs would include these components:
Nonporous roof material. Although all roofs shed water, surfaces that have a lot of nooks and crannies are more likely to pick up debris and support the growth of mold, increasing the need for filtering and treatment. A nonporous surface like metal (for example, Galvalume Plus with an acrylic coating) is a much better option.
Gutters and downspouts. Six-inch gutters and five-inch downspouts should be able to handle all the rain that Mother Nature provides.
Cistern. A storage tank of up to 40,000 gallons may be required if a homeowner intends to rely on rainwater exclusively. In-ground concrete tanks are easy to camouflage and don’t need much maintenance.
Filters. Sediment filters and UV filters clean the water once it’s pumped from the cistern to the house, making it suitable for drinking, cooking and bathing.
- Peter L. Pfeiffer/Fine Homebuilding #142
- Dan Thornton/Fine Homebuilding #142