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32 Estimating Economic Impacts of Salinity... N ~-J o (0 as a major catalyst for corrosion - Wl::l.ter high in dissolved minerals is not particularly corrosive if no dissolved oxygen is present. The Handbook recommends increasing the presence of calcium carbonate to form a protective scale in water sys- tem pipes. Certainly the studies conducted on water quality damages to consumers indicate the efficacy of CaC03 in protecting home piping and hot water heaters, etc. Each of the studies that made comparisons found failure rates increasing as home water softening increased. Water softening by ion exchange, which substitutes sodium for calcium in hard water, increases the effectiveness of soaps, and feels softer against the skin, but it also prevents formation of protec- tive scale, increases the sodium coutent of drink- ing water, and may affect the taste. Hardness. Hardness in water is a term that means the presence of a significant level of calcium and magnesium ions, i.e., dissolved compounds, usu~ ally chlorides, carbonates, sulfates, and (if the water is alkaline) bicarbonates. These hardness constituents (Ca and Mg) cause ordinary soaps to precipitate from solution, and may themselves form calcium or magnesium compounds that precipitate and form scale. Data from water quality analyses from 1973 to the present indicate a very close and consis- tent relationship between salinity and hardness in Colorado River water. In the TDS range of 675-720 mgiL (approximate to ppm) hardness (in ppm) ranges from 45 percent to 49 percent of the TDS value. In the 300-550 mgiL TDS range, hardness varies from 49 percent to 53 percent of the TDS value. A study by Battelle Laboratories18 confirms that scale build-up on water heaters provides benefits in offsetting corrosion, as well as damages. It noted that softened water effectively reduced scale but accelerated corrosion in water heaters. Although the scale buildup over 20 years of use could reduce efficiency by 4.2 per- cent, minimizing corrosion was of more benefit to appliance life. On the other hand, a use and care book accompanying a GE washing machine19 discus- ses the problem of "limestone" deposits resulting from a combination of hard water and non- phosphate detergent. The booklet recommends using a phosphate detergent, installing a water softener, or using a packaged water softener with phosphate. It also recommends using hotter water, but no vinegar to change pH. Needless to say, consumers get more concerned about lime- stone buildup than about the formation of protective scale. Damages. In essence, most water-related household damages occur from corrosion - a complex kinetic occurrence that mayor may not be re- lated to TDS - or from scale formation which is directly related to hardness. Water from the Colorado River is generally hard to very hard, and its hardness is directly proportional to the TDS level of the water. Scale and hardness of home water appear to be the factors that most concern the average consumer. Corrosion, on the other hand, can cause the more severe economic losses. Responses to water hardness include such measures as water softening with a resulting pur- chase of bottled water, purcbase of additional laundry additives, or tap ftIters. The response to corrosion is likely to be premature replacement of plumbing systems and various water-using appliances or parts. Part of the response on the part of con- sumers is a direct result of sales pressure. Manufacturers and purveyors of home water treatment systems and bottled water advertise heavily. These factors, combined with the recent increase of attention to the safety of water in terms of toxic waste and other (than salinity) con- taminants, have led to an increase in home water treatment systems and in the sale of bottled water. Bottled water is a particularly interesting case of consumer costs. A number of the studies 18Battelle Columbus Laboratories, Th~ Fffert nf WAf,.." 011::111'1 on Rel::iilp.ntiAI WAf,.,. Hp.l\tel' T irt~.l)r'f': Fffir.ip.t1~ Thircl Annul'll Report (September 19M. AU~lI"f 19R~), Chicago: Gas Research Institute, 1985. 19Excerpt or GE Use and Care Pamphlet on Washers, from Air-Conditioning and Refrigeration Institute, 1501 Wilson Blvd., Arlington, Virginia.