Conservation Information

How to Conserve Water and Use It Effectively

Practices for Residential Users

The following are examples of conservation and water use efficiency practices that can benefit residential users.

Plumbing. An engineering practice for individual residential water users is the installation of indoor plumbing fixtures that save water or the replacement of existing plumbing equipment with equipment that uses less water. Low-flow plumbing fixtures and retrofit programs are permanent, one-time conservation measures that can be implemented automatically with little or no additional cost over their life times. In some cases, they can even save the resident money over the long term. The City of Corpus Christi, for example, has estimated that an average three-member household can reduce its water use by 54,000 gallons annually and can lower water bills by about $60 per year if water-efficient plumbing fixtures are used.

Low-Flush Toilets. Residential demands account for about three-fourths of the total urban water demand. Indoor use accounts for roughly 60 percent of all residential use, and of this, toilets (at 3.5 gallons per flush) use nearly 40 percent. Toilets, showers, and faucets combined represent two-thirds of all indoor water use. More than 4.8 billion gallons of water is flushed down toilets each day in the United States. The average American uses about 9,000 gallons of water to flush 230 gallons of waste down the toilet per year. In new construction and building rehabilitation or remodeling there is a great potential to reduce water consumption by installing low-flush toilets.

Conventional toilets use 3.5 to 5 gallons or more of water per flush, but low-flush toilets use only 1.6 gallons of water or less. Since low-flush toilets use less water, they also reduce the volume of wastewater produced. Even in existing residences, replacement of conventional toilets with low-flush toilets is a practical and economical alternative. The effectiveness of low-flush toilets has been demonstrated in a study in the City of San Pablo, California. In a 30-year-old apartment building, conventional toilets that used about 4.5 gallons per flush were replaced with low-flush toilets that use approximately 1.6 gallons per flush. The change resulted in a decrease in water consumption from approximately 225 gallons per day per average household of 3® persons to 148 gallons per day per household a savings of 34 percent! Although the total cost for replacement of the conventional toilets with low-flush toilets was about $250 per unit (including installation), the water conservation fixtures saved an average of $46 per year from each unit’s water bill. Therefore, the cost for the replacement of the conventional toilet with a low-flush toilet could be recovered in 5.4 years.

Toilet Displacement Devices. Plastic containers (such as plastic milk jugs) can be filled with water or pebbles and placed in a toilet tank to reduce the amount of water used per flush. By placing one to three such containers in the tank (making sure that they do not interfere with the flushing mechanisms or the flow of water), more than l gallon of water can be saved per flush. A toilet dam, which holds back a reservoir of water when the toilet is flushed, can also be used instead of a plastic container to save water. Toilet dams result in a savings of 1 to 2 gallons of water per flush.

Low-Flow Showerheads. Showers account for about 20 percent of total indoor water use. By replacing standard 4.5-gallon-per-minute showerheads with 2.5-gallon-per-minute heads, which cost less than $5 each, a family of four can save approximately 20,000 gallons of water per year. Although individual preferences determine optimal shower flow rates, properly designed low-flow showerheads are available to provide the quality of service found in higher-volume models.

Faucet Aerators. Faucet aerators, which break the flowing water into fine droplets and entrain air while maintaining wetting effectiveness, are inexpensive devices that can be installed in sinks to reduce water use. Aerators can be easily installed and can reduce the water use at a faucet by as much as 60 percent while still maintaining a strong flow. More efficient kitchen and bathroom faucets that use only 2 gallons of water per minute–unlike standard faucets, which use 3 to 5 gallons per minute–are also available (Jensen, 1991).

Pressure Reduction. Because flow rate is related to pressure, the maximum water flow from a fixture operating on a fixed setting can be reduced if the water pressure is reduced. For example, a reduction in pressure from 100 pounds per square inch to 50 psi at an outlet can result in a water flow reduction of about one-third.

Homeowners can reduce the water pressure in a home by installing pressure-reducing valves. The use of such valves might be one way to decrease water consumption in homes that are served by municipal water systems. For homes served by wells, reducing the system pressure can save both water and energy. Many water use fixtures in a home, however, such as washing machines and toilets, operate on a controlled amount of water, so a reduction in water pressure would have little effect on water use at those locations.

A reduction in water pressure can save water in other ways: it can reduce the likelihood of leaking water pipes, leaking water heaters, and dripping faucets. It can also help reduce dishwasher and washing machine noise and breakdowns in a plumbing system.

A study in Denver, Colorado, illustrates the effect of water pressure on water savings. Water use in homes was compared among different water pressure zones throughout the city. Elevation of a home with respect to the elevation of a pumping station and the proximity of the home to the pumping station determine the pressure of water delivered to each home. Homes with high water pressure were compared to homes with low water pressure. An annual water savings of about 6 percent was shown for homes that received water service at lower pressures when compared to homes that received water services at higher pressures.

Gray Water Use. Domestic wastewater composed of wash water from kitchen sinks and tubs, clothes washers, and laundry tubs is called gray water. Gray water can be used by homeowners for home gardening, lawn maintenance, landscaping, and other innovative uses. The City of St. Petersburg, Florida, has implemented an urban dual distribution system for reclaimed water for nonpotable uses. This system provides reclaimed water for more than 7,000 residential homes and businesses.

Landscaping. Lawn and landscape maintenance often requires large amounts of water, particularly in areas with low rainfall. Outdoor residential water use varies greatly depending on geographic location and season. On an annual average basis, outdoor water use in the arid West and Southwest is much greater than that in the East or Midwest. Nationally, lawn care accounts for about 32 percent of the total residential outdoor use. Other outdoor uses include washing automobiles, maintaining swimming pools, and cleaning sidewalks and driveways.

Landscape Irrigation. One method of water conservation in landscaping uses plants that need little water, thereby saving not only water but labor and fertilizer as well. A similar method is grouping plants with similar water needs. Scheduling lawn irrigation for specific early morning or evening hours can reduce water wasted due to evaporation during daylight hours. Another water use efficiency practice that can be applied to residential landscape irrigation is the use of cycle irrigation methods to improve penetration and reduce runoff. Cycle irrigation provides the right amount of water at the right time and place, for optimal growth. Other practices include the use of low-precipitation-rate sprinklers that have better distribution uniformity, bubbler/soaker systems, or drip irrigation systems.

Xeriscape Landscapes. Careful design of landscapes could significantly reduce water usage nationwide. Xeriscape landscaping is an innovative, comprehensive approach to landscaping for water conservation and pollution prevention. Traditional landscapes might incorporate one or two principles of water conservation, but xeriscape landscaping uses all of the following: planning and design, soil analysis, selection of suitable plants, practical turf areas, efficient irrigation, use of mulches, and appropriate maintenance.

Benefits of xeriscape landscaping include reduced water use, decreased energy use (less pumping and treatment required), reduced heating and cooling costs because of carefully placed trees, decreased storm water and irrigation runoff, fewer yard wastes, increased habitat for plants and animals, and lower labor and maintenance costs.

Behavioral Practices. Behavioral practices involve changing water use habits so that water is used more efficiently, thus reducing the overall water consumption in a home. These practices require a change in behavior, not modifications in the existing plumbing or fixtures in a home. Behavioral practices for residential water users can be applied both indoors in the kitchen, bathroom, and laundry room and outdoors.

In the kitchen, for example, 10 to 20 gallons of water a day can be saved by running the dishwasher only when it is full. If dishes are washed by hand, water can be saved by filling the sink or a dishpan with water rather than running the water continuously. An open conventional faucet lets about 5 gallons of water flow every 2 minutes.

Water can be saved in the bathroom by turning off the faucet while brushing teeth or shaving. Water can be saved by taking short showers rather than long showers or baths and turning the water off while soaping. This water savings can be increased even further by installing low-flow showerheads, as discussed earlier. Toilets should be used only to carry away sanitary waste.

Households with lead-based solder in pipes that flush the first several gallons of water should collect this water for alternative nonpotable uses (e.g., plant watering).

Water can be saved in the laundry room by adjusting water levels in the washing machine to match the size of the load. If the washing machine does not have a variable load control, water can be saved by running the machine only when it is full. If washing is done by hand, the water should not be left running. A laundry tub should be filled with water, and the wash and rinse water should be reused as much as possible.

Outdoor water use can be reduced by watering the lawn early in the morning or late in the evening and on cooler days, when possible, to reduce evaporation. Allowing the grass to grow slightly taller will reduce water loss by providing more ground shade for the roots and by promoting water retention in the soil. Growing plants that are suited to the area (“indigenous” plants) can save more than 50 percent of the water normally used to care for outdoor plants.

As much as 150 gallons of water can be saved when washing a car by turning the hose off between rinses. The car should be washed on the lawn if possible to reduce runoff.

Additional savings of water can result from sweeping sidewalks and driveways instead of hosing them down. Washing a sidewalk or driveway with a hose uses about 50 gallons of water every 5 minutes. If a home has an outdoor pool, water can be saved by covering the pool when it is not in use.

Practices for Industrial/Commercial Users

Industrial/commercial users can apply a number of conservation and water use efficiency practices.

Water Reuse and Recycling
Water reuse is the use of wastewater or reclaimed water from one application such as municipal wastewater treatment for another application such as landscape watering. The reused water must be used for a beneficial purpose and in accordance with applicable rules (such as local ordinances governing water reuse). Some potential applications for the reuse of wastewater or reclaimed water include other industrial uses, landscape irrigation, agricultural irrigation, aesthetic uses such as fountains, and fire protection. Factors that should be considered in an industrial water reuse program include:

• Identification of water reuse opportunities
• Determination of the minimum water quality needed for the given use
• Identification of wastewater sources that satisfy the water quality requirements
• Determination of how the water can be transported to the new use

The reuse of wastewater or reclaimed water is beneficial because it reduces the demands on available surface and ground waters. Perhaps the greatest benefit of establishing water reuse programs is their contribution in delaying or eliminating the need to expand potable water supply and treatment facilities. Water recycling is the reuse of water for the same application for which it was originally used. Recycled water might require treatment before it can be used again. Factors that should be considered in a water recycling program include:

• Identification of water reuse opportunities
• Evaluation of the minimum water quality needed for a particular use
• Evaluation of water quality degradation resulting from the use
• Determination of the treatment steps, if any, that might be required to prepare the water for recycling

Cooling Water Recirculation
The use of water for cooling in industrial applications represents one of the largest water uses in the United States. Water is typically used to cool heat-generating equipment or to condense gases in a thermodynamic cycle. The most water-intensive cooling method used in industrial applications is once-through cooling, in which water contacts and lowers the temperature of a heat source and then is discharged.

Recycling water with a recirculating cooling system can greatly reduce water use by using the same water to perform several cooling operations. The water savings are sufficiently substantial to result in overall cost savings to the industry. Three cooling water conservation approaches that can be used to reduce water use are evaporative cooling, ozonation, and air heat exchange.

In industrial/commerical evaporative cooling systems, water loses heat when a portion of it is evaporated. Water is lost from evaporative cooling towers as the result of evaporation, drift, and blowdown. (Blowdown is a process in which some of the poor-quality recirculating water is discharged from the tower in order to reduce the total dissolved solids.) Water savings associated with the use of evaporative cooling towers can be increased by reducing blowdown or water discharges from cooling towers.

The use of ozone to treat cooling water (ozonation) can result in a five-fold reduction in blowdown when compared to traditional chemical treatments and should be considered as an option for increasing water savings in a cooling tower.

Air heat exchange works on the same principle as a car’s radiator. In an air heat exchanger, a fan blows air past finned tubes carrying the recirculating cooling water. Air heat exchangers involve no water loss, but they can be relatively expensive when compared with cooling towers.

The Pacific Power and Light Company’s Wyodak Generating Station in Wyoming decided to use dry cooling to eliminate water losses from cooling-water blowdown, evaporation, and drift. The station was equipped with the first air-cooled condenser in the western hemisphere. Steam from the turbine is distributed through overhead pipes to finned carbon steel tubes. These are grouped in rectangular bundles and installed in A-frame modules above 69 circulating fans. The fans force some 45 million cubic feet per minute (ft3/min) of air through 8 million square feet of finned-tube surface, condensing the steam. The payback comes from the water savings. Compared to about 4,000 gallons per minute (gal/min) of makeup (replacement water) for equivalent evaporative cooling, the technique reduces the station’s water requirement to about 300 gal/min.

Rinsing
Another common use of water by industry is the application of deionized water for removing contaminants from products and equipment. Deionized water contains no ions (such as salts), which tend to corrode or deposit onto metals. Historically, industries have used deionized water excessively to provide maximum assurance against contaminated products. The use of deionized water can be reduced without affecting production quality by eliminating some plenum flushes (a rinsing procedure that discharges deionized water from the rim of a flowing bath to remove contaminants from the sides and bottom of the bath), converting from a continuous-flow to an intermittent-flow system, and improving control of the use of deionized water.

Deionized water can be recycled after its first use, but the treatment for recycling can include many of the processes required to produce deionized water from municipal water. The reuse of once-used deionized water for a different application should also be considered by industry, where applicable, because deionized water is often more pure after its initial use than municipal water.

Landscape Irrigation
Another way that industrial/commercial facilities can reduce water use is through the implementation of efficient landscape irrigation practices. There are several general ways that water can be more efficiently used for landscape irrigation, including the design of landscapes for low maintenance and low water requirements (refer to the previous section on xeriscape landscaping), the use of water-efficient irrigation equipment such as drip systems or deep root systems, the proper maintenance of irrigation equipment to ensure that it is working properly, the distribution of irrigation equipment to make sure that water is dispensed evenly over areas where it is needed, and the scheduling of irrigation to ensure maximum water use.

Behavioral Practices
Behavioral practices involve modifying water use habits to achieve more efficient use of water, thus reducing overall water consumption by an industrial/commercial facility. Changes in behavior can save water without modifying the existing equipment at a facility.

Monitoring the amount of water used by an industrial/commercial facility can provide baseline information on quantities of overall company water use, the seasonal and hourly patterns of water use, and the quantities and quality of water use in individual processes. Baseline information on water use can be used to set company goals and to develop specific water use efficiency measures. Monitoring can make employees more aware of water use rates and makes it easier to measure the results of conservation efforts. The use of meters on individual pieces of water-using equipment can provide direct information on the efficiency of water use. Records of meter readings can be used to identify changes in water use rates and possible problems in a system.

Many of the practices described for residential users above can also be applied by commercial users. These include low-flow fixtures, water-efficient landscaping, and water reuse and recycling (e.g., using recycled wash water for pre-rinse).

Practices for Agricultural Users

Irrigation
Water-saving irrigation practices fall into three categories: field practices, management strategies, and system modifications. Field practices are techniques that keep water in the field, distribute water more efficiently across the field, or encourage the retention of soil moisture. Examples of these practices include the chiseling of extremely compacted soils, furrow diking to prevent runoff, and leveling of the land to distribute water more evenly. Typically, field practices are not very costly.

Management strategies involve monitoring soil and water conditions and collecting information on water use and efficiency. The information helps in making decisions about scheduling applications or improving the efficiency of the irrigation system. The methods include measuring rainfall, determining soil moisture, checking pumping plant efficiency, and scheduling irrigation.

System modifications require making changes to an existing irrigation system or replacing an existing system with a new one. Because system modifications require the purchase of equipment, they are usually more expensive than field practices and management strategies. Typical system modifications include adding drop tubes to a center pivot system, retrofitting a well with a smaller pump, installing surge irrigation, or constructing a tailwater recovery system.

Water Reuse and Recycling
Agricultural irrigation represents approximately 40 percent of the total water demand nationwide. Given that high demand, significant water conservation benefits could result from irrigating with reused or recycled water.

Water reuse is the use of wastewater or reclaimed water from one application for another application. Reused water must be used for a beneficial purpose and in accordance with applicable rules. Water recycling is the reuse of water for the same application for which it was originally intended.

Factors that should be considered in an agricultural water reuse program include:

• The identification of water reuse opportunities
• Determination of the minimum water quality needed for the given use
• Identification of wastewater sources that satisfy the water quality requirements
• Determination of how the water can be transported to the new use

Water reuse for irrigation is already in widespread use in rural areas and is also applicable in areas where agricultural sites are near urban areas and can easily be integrated with urban reuse applications.

Behavioral Practices
Behavioral practices involve changing water use habits to achieve more efficient use of water. Behavioral practices for agricultural water users can be applied to irrigation application rates and timing. Changes in water use behavior can be implemented without modifying existing equipment.

For example, better irrigation scheduling can result in a reduction in the amount of water that is required to irrigate a crop effectively. The careful choice of irrigation application rates and timing can help farmers to maintain yields with less water. In making scheduling decisions, irrigators should consider:

• The uncertainty of rainfall and crop water demand
• The limited water storage capacity of many irrigated soils
• The limited pumping capacity of irrigation systems
• Rising pumping costs as a result of higher energy prices

Local NRCS-Conservation Districts and Cooperative Extension Service offices can play an important role in promoting better irrigation scheduling. Accurate information on crop water use requires information on solar radiation and other weather variables that can be collected by local weather stations. An additional method that can be used to improve irrigation scheduling and might result in high returns is the use of equipment such as resistance blocks, tensiometers, and neutron probes to monitor soil moisture conditions to help in determining when water should be applied.

Source: US Environmental Protection Agency (www.epa.gov/)