WQ1031 (Revised) It’s All In Your Water 2017 EDITION Water Softening (Ion Exchange)

Tom Scherer, Ph.D. What Makes believe they have a problem Extension Agricultural Engineer Water “Hard”? when hardness surpasses the North Dakota State University 6 to 7 grains-per-gallon level. So-called “hard” water is the result of ground water passing through and dissolving rocks and minerals, which Problems Caused Standard water softeners then release calcium and magnesium by Hard Water found in home supply and ions. These dissolved ions give hard Hard water interferes with all types hardware stores will remove water its characteristics. of cleaning tasks. Cleaning problems nearly all the calcium and arise when the cleaning agents do magnesium from the raw water How is Hardness not fully remove dirt and grime. during the softening process. Measured? Through time, clothes washed in Softeners also will remove up hard water may look dingy and feel Water hardness is expressed in to 10 parts per million (ppm) harsh and scratchy. White clothing grains of hardness per gallon (gpg) continually washed in hard water of iron and manganese. of water or as parts per million (ppm) gradually will become dingy. Water supplies with high or milligrams per liter (mg/l). levels of iron and manganese One gpg is equal to 17 ppm (mg/l). Dishes and glassware washed in (greater than 10 ppm) Table 1 shows how hardness dishwashers using hard water may may need pretreatment is classified. According to NSF be spotted when dry. Hard water to prolong the lifespan International, a public health and causes films on glass shower doors, of a water softener. safety organization, consumers walls and bathtubs. Hair washed in hard water may feel sticky and look Table 1. Hardness Classification dull. After showering in hard water, (hardness as calcium carbonate). skin will feel rough and scratchy. This feeling is especially noticeable Mg/l Grains per or ppm Gallon (gpg) in the winter when the air’s relative humidity is low. Soft Less than 17 Below 1.0 Slightly hard 17-60 1.0 to 3.5 Scum occurs when soap combines Moderately hard 61-120 3.5 to 7.0 with dissolved calcium and magnesium. Soap scum is difficult Hard 121-180 7.0 to 10.5 to remove from sinks, showers, Very hard More than Above 10.5 bathtubs and other appliances. August 2017 Hard water use may affect the Community water supplies are performance of household appliances. monitored and treated to protect When heated, calcium carbonate and users from health-threatening water magnesium carbonate settle out of impurities. Ask your supplier for a suspension (precipitate) from the copy of the latest water test results. water and form a mineral deposit at Hard water is considered a nuisance the bottom of the hot water heater. A water problem. Hardness removal large scale buildup slows the heating is not a necessity to protect your process and requires more energy to health, but water softening is heat water. Water heaters with large popular because most people accumulations of mineral buildup will prefer softened water for bathing, have a shorter life span. Scale deposits cleaning and washing. also accumulate to plug plumbing fix- tures and build up in other appliances Figure 1. Softening process. Health Risks Associated such as coffee pots and dishwashers, (Adapted by D. Baer, 2012.) thus affecting their performance. With Softened Water the exchange medium must be During the softening process, sodium The Ion Exchange Process recharged or regenerated (Figure 1). is released from the exchange media into the output water. For every grain Calcium (Ca2+) and magnesium To recharge the softener with sodium of hardness removed from water, (Mg2+) ions that cause water hardness ions, a softener is backflushed with 8 mg/1 (ppm) of sodium is added. can be removed fairly easily by using a salt brine solution. During a People on restricted sodium intake an ion exchange procedure. Standard backflush, the brine solution diets should account for increased water softeners are cation exchange replaces the calcium and magnesium levels of sodium in softened water. devices. Cations refer to positively ions on the exchange medium with Your family physician should be charged ions dissolved in the water. sodium ions from the salt solution. consulted. Cation exchange involves the replacement of the hardness ions Recharging Process Sodium intake from softened with a nonhardness ion. The time between recharging cycles water can be avoided by leaving one kitchen tap unsoftened for Water softeners usually use sodium depends on the hardness of the water, drinking and cooking. Substituting (Na+) as the exchange ion. Sodium the amount of water used, the size potassium chloride for sodium ions are supplied from dissolved of the unit and the capacity of the chloride may be appropriate if sodium chloride salt, also called brine. exchange media to remove hardness. health or environmental reasons In the ion exchange process, sodium necessitate restricting sodium. ions are used to coat an exchange Have Your Water Tested medium in the softener. The exchange Before buying any water treatment Potassium chloride is more medium can be natural “zeolites” or equipment, you should know what expensive and adheres more strongly synthetic resin beads that resemble impurities are in the water supply. to the resin, reducing the exchange wet sand. A certified laboratory can determine efficiency when compared with sodium chloride. About 10 percent As hard water passes through a the types and amounts of impurities more potassium chloride salt is used softener, the calcium and magnesium in your water. A list of certified labs during the backflush operation. trade places with sodium ions is available in the NDSU publication (Figure 1). Sodium ions are held “Drinking Water Quality: Testing and loosely and are replaced easily Interpreting Your Results” (WQ1341). Types of Water-softening by calcium and magnesium ions. The results of the water test will help Equipment Available During this process, “free” sodium determine if softening is needed. The primary difference among ions are released into the water. The water testing may reveal if water softener models is in the way other water treatment is required. they schedule the backflush cycles. Softening Process If you obtain water from a private This is important because recharging After softening a large quantity of water supply, water testing is your the beads with salt too early wastes hard water, the exchange medium responsibility. Water testing should salt and water. Recharging too late becomes coated with calcium and be done on a regular basis. If you causes performance to fall off. magnesium ions. When this occurs, suspect a problem, test more often. Water softeners are classified into equipment may be required Alternatives to four different categories: (see the NDSU publication “Iron Ion Exchange Units and Manganese” (AE1030) at • Semiautomatic: The operator Hard water problems can be reduced www.ag.ndsu.edu/pubs/watsys.html). initiates only the recharging cycle. by using detergents that include Water test results will help make The operator pushes a button when water-softening chemicals in their that determination. the softener needs recharging, and formulation. Some types of chemicals the unit will control and complete More frequent backflushing can be added to hard water to reduce the recharging process. (reversing the normal flow of water the negative effect of calcium and • Automatic: Automatic softeners through the treatment unit) may be magnesium. Chemical treatment for have a timer that automatically required to remove iron buildup. household water softening is recom- initiates the recharging cycle mended for low levels of hardness. and every step in the process. Cost of Water Softeners Two types of chemicals used to The operator sets the timer and and Supplies soften water for home laundry adds salt as needed. This is the Retail prices for home water softeners are Sal Soda and Calgon. most common type of softener used. may range from approximately Sal Soda combines with calcium and • Demand-initiated regeneration $400 to $2,700, depending on the size magnesium to form solid particles. (DIR): All operations are initiated and type of softener. Softeners are These particles settle out with and performed automatically in rated by the total number of grains particles of dirt during washing. response to the water use demand the unit can remove before being Use of precipitating additives such for softened water. DIR systems recharged. The cost of salt is as Sal Soda may not fully clean your generally have two softening approximately $5 to $8 per 40-pound laundry because solid particles may tanks and a brine tank. While bag of sodium chloride (NaCl), cling to fabrics. one tank is softening, the other depending on the form purchased, tank is recharging. and up to $25 per 40-pound bag Calgon softens water by combining • Off-site regeneration (generally for potassium chloride (KCl). with calcium and magnesium to rental units): A used softening tank form compounds that stay in is replaced with a recharged tank. Advantages of solution. The use of nonprecipitating Spent softening tanks then are Water Softeners additives such as Calgon has a negative environmental effect recharged at a central location. Softeners offer cleaner, softer feeling because they have high phosphate clothes; longer life of appliances, content that promotes algae growth Operation and including washing machine, in local waters. Maintenance dishwasher and water heater; less Maintenance of water softeners use of household cleaning products, largely is confined to restocking the such as detergents, as well as personal Magnetic Conditioning salt supply for the brine solution. With cleanliness products such as shampoo; Permanent magnetic water semiautomatic models, the owner also and reduction of water spotting. conditioning devices have been will have to start the recharging cycle. marketed based on a variety of Salt can be purchased in the form of Disadvantages of claims regarding their effect on pellets, granules or blocks. Water Softeners water hardness and related scale formation. The Water Quality The brine tank may require periodic Softened water is not recommended Association, a not-for-profit trade cleaning. The frequency of cleaning for watering house plants, lawns and association for the water treatment depends on the amount and purity of gardens due to its sodium content. industry, has not been able to deter- the salt used in the softening process. Water used in recharging a water mine standards for these products The brine valve and float assembly softener may overload or reduce the and report inconsistent performance also should be checked and cleaned effectiveness of small septic or sewer to date. Research has shown no as often as needed. systems. Sodium intake may pose change occurs in the physical health risks. Softened water is not The presence of excess iron or and chemical properties or the recommended for steam irons or hydrogen sulfide can inhibit the calcium ion concentration of evaporative coolers. The best choice effectiveness of a water-softening water treated with the devices for such appliances is distilled water unit. Installation of the iron-removal (The Water Quality Association or water from a reverse osmosis unit. Magnetics Task Force, 2001). Items to Consider When Purchasing an Ion Exchange Water Softener References Gruber, C.E., and D.D. Carda. 1981. Measurable • Test your water to determine the hardness and parameters in water conditioning equipment as other impurities that may need to be removed. determined in laboratory simulations at Rapid City, S.D. • Determine how much softened water your household Final report issued to the Water Quality Association. needs per day, per year. South Dakota School of Mines and Technology. www.wqa.org/sitelogic.cfm?id=2 • What type and size of softener will fit your situation? Water Quality Association. WQA Magnetics Task Force Report. (2001). • How easy is the softener to clean and/or repair? The Water Quality Association Magnetics • Will the dealer provide service? Task Force. Water Quality Association (Order No. R20, FGI-3M) (Pamphlet). Lisle, Ill. • What type of convenience level should a softener www.wqa.org/pdf/GovRelations/WQAMagneticsTaskForceReport.pdf offer (manual or automatic operation)? Private Water Systems Handbook. (5th Ed.) • Will pretreatment be needed for iron and manganese? MWPS-14. Midwest Plan Service. • Will sodium intake be a health problem? ISBN 0-89373-105-6. April 2009. • Will sodium salts overload your septic or sewer system? • Investigate equipment before purchasing or renting. Further Information Don’t rush a purchase. For further information, contact your local county Extension office • The purchase price does not directly indicate a or state health department. softener’s performance. A moderately priced unit Additional information can be might work as well as an expensive unit. found in these publications: • When buying or renting, are the installation costs included in the price? • WQ1029 Filtration: Sediment, Activated Carbon and • Don’t buy more equipment than you need. Mixed Media Other removal systems might be better suited • WQ1030 Iron and Manganese for the removal of certain impurities. Removal • Choose a reputable dealer. Get guarantees in • WQ1341 Drinking Water Quality: writing and read them thoroughly. Testing and Interpreting • Beware of manufacturers’ advertising that is Your Results too good to be true. • WQ1352 What’s Wrong • Equipment should carry UL and NSF or With My Water? WQA approval. Choose the Right Test

This publication was authored by Roxanne Johnson, former Water Quality Associate, and Tom Scherer

The NDSU Extension Service does not endorse commercial products or companies even though reference may be made to trade names, trademarks or service names.

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