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Here come the cisterns again.

Here come the cisterns again Before modern methods of piping water into homes existed, cisterns--large tanks or reservoirs for storing water--were common sights in households from ancient Egypt to gold rush California. Around the turn of the century, most country homes in the United States still used cisterns to provide water.

With the development of piped-in water in major cities in the mid-1800s, water used skyrocketed from 3 gallons of water per person per day to 40 to 60 gallons. Now, the average home uses 150 to 200 gallons per person per day. With increasing demands on community water systems, escalating water costs, and possible contamination of water from industrial waste, captured rainfall offers a usable source of high-quality water.

Cisterns come in all sizes and shapes, from simple rain barrels to elaborate underground systems that collect, filter, and store water. From California to New Mexico, gardeners collect hundres to thousands of gallons annually by using the innovative techniques shown on these five pages.

Use captured rainfall

to green your garden One of the first areas to suffer or to be e targeted for conservation in times of drought is the garden. Dpending on its size and the plants' water demands, 45 to 70 percent of household water consumption is for the landscape. Many cites in the arid West already have some conservation measures in effect. By collecting rainfall, gardeners can keep their landscapes green without incurring high water bills or surpassing community limits set by water districts.

Cisterns can also protect investments in expensive landscaping against temporary expensive landscaping against temporary droughts, and provide an emergency supply of water. Although studies show that Western rainfall has increased in acidity in recent years, rainwater is not a danger to home gardens. Many Southwestern gardens have the opposite problem--tap water with such a high mineral content that it may burn some plants.

With additional plumbing and adequate storage space, the collected water can also be used for laundry and toilets. But unless you test its quality and purify it, don't consume capture rainfall.

Anyone with a roof can capture rainfall

The amount of annual rainfall and the sixe of the catchment surface--roofs, driveways, patios--determine how much water can be collected yearly. The roof of a modest-size house in an area with moderate rainfall (18 inches annually--the average amount received by much of the central California coast) can collect about 12,000 gallons of water a year.

Simple calculations and graphs can help you figure how much water you can collect and how much is needed by a household (for a list of helpful references, see page 260). However, most houses don't have enough space to store more than a few thousand gallons of water. In the future, neighborhood systems may turn out to be a cost-efficient source of high-quality water.

Parts of a system

Underground and aboveground cisterns use the same methods to catch and channel water to the collection area. Beyond this point, the systems differ in the way they filter and store it. Aboveground cisterns are easier and less expensive to install since the tank isn't buried and the filter is just a simple piece of screen set in the gutter system. On the other hand, underground cisterns are generally considered more permanent.

The catchment surface. This can be a roof, driveway, patio, or road. Before a rainy period, they must be cleaned of leaves and debris to prevent the system from clogging. It's best to let the first flush of water bypass the system to wash away dust and debris. If you collect water from a driveway, keep engine oil and other chemicals off the pavement.

Channeling the water. Roof gutters, downspouts, and PVC pipe can channel water to the cistern. Gutters should be 5 inches wide and have a minimum slope of 1/8 inch per foot. Round downspouts are easier to remove for cleaning and, if left unglued, can be rotated away from the cistern to dispose of the season's first rain. To keep out debris, place a 1/4-inch-mesh screen above where the downspout connects to the gutter and clean it regularly. To direct water from downspouts and carry it to an underground container, use 4-inch-diameter PVC pipe.

The storage tank. Almost any container that holds water can be used as a cistern. It should be free of chemical residue and opaque to prevent algae growth. High-density polyethylene tanks, like those designed to store chemicals (see photograph on page 254), last the longest. Fiberglass, wood barrels, and metal drums also work but are less durable. Keep the containers covered to reduce evaporation, keep out debris and insects, and prevent algae growth; flush the tanks periodically to remove sediments and prevent clogging.

Tanks should have an entrance hole for the source, a screened pipe or hole for overflow, an outlet pipe and valve, and preferably an access hole or hinged lid for cleaning (although an adequate screen filter may make cleaning unnecessary).

Suppliers are listed under "Tanks" in the yellow pages. You could save money buying a used tank, but unless you can be certain what it was used for, this is not a good idea.

For an aboveground system, you might want more than one tank around the house; it's easier to deliver water to sections of the gardens when tanks are close to the demand area. Tanks below downspouts can be siphoned off to other tanks in the garden, such as one near a vegetable garden.

If feasible, locate the cistern at a higher elevation than the plants to be watered so the water runs out by gravity. Otherwise, use a small pump to deliver it to plants, as shown at the top of page 254.

To help disguise the tank, you can conceal it with shrubs or a lattice screen, or fence it as shown in the same photograph.

Underground cisterns can be simple systems with a hand-operated valve for removing water (see photograph below) or advanced designs where water is filtered and delivered to an automatic irrigation system (see photographs on page 256). Advanced systems should be installed by a specialist.

Getting more information

For professional advice, call in a landscape architect. Your city water department may have a conservation officer who can help you find someone that specializes in cistern design.

For more detailed technical information on designing a system to meet your household needs, see Captured Rainfall: Small-Scale Water Supply Systems, Bulletin 213 (California Department of Water Resources, Box 388, Sacramento 95802, 1981; $1 plus California sales tax); The Home Water Supply: How to Find, Filter, Store, and Conserve It, by S. Campbell (Storey Communications Inc., Schoolhouse Rd., Pownal, Vt. 05261, 1983; $12.95 plus $2 shipping); and Residential Water Re-use, Report 46, by Murray Milne (California Water Resources Center, University of California, Davis 95616, 1979; $10 including tax).
COPYRIGHT 1986 Sunset Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1986 Gale, Cengage Learning. All rights reserved.

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Date:Nov 1, 1986
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