Softening Up Hard Water
The minerals in hard water form a hard scale that can shorten the life of plumbing fixtures and appliances. For example, scale build-up can decrease the life of toilets by 70 percent and faucets by 40 percent, according to a report published by the American Water Works Association. Hardness scale can also shorten the life of washing equipment, dishwashers, and washing machines by as much as 30 percent, according to the AWWA report.
Scale also tends to form on the heating elements and heat-transfer surfaces of water heaters. A New Mexico State University study determined that scale build-up can reduce a gas water heater's efficiency by as much as 29.57 percent, and an electric water heater's efficiency by as much as 21.68 percent. Another study conducted by the Office of Saline Water, U.S. Department of the Interior, found that a water heater's useful life can be reduced by as much as 50 percent through scale build-up.
What Is Hard Water?The problems associated with hard water have been known for quite some time. Earlier generations coined the phrase “hard water” because they found it hard to clean with. They collected soft rainwater in a barrel to be used in laundering and other cleaning operations - hardly an option in the modern world.
Some water utilities offer municipal softening, but water treated in this manner typically falls short of being soft water. It is generally left up to you to help your customers find an individual solution.
The U.S. Department of the Interior classifies water hardness based on the grains per gallon (gpg) concentration of hardness minerals, typically calcium and/or magnesium. To put this in perspective, a typical aspirin equals about 5 grains of material. So if you dissolved an aspirin in a gallon of water, the water would contain 5 gpg of aspirin. That doesn't sound like much, but such a minor level would be enough to make water hard.
Water containing 1-3.5 gpg of calcium and/or magnesium is classified as slightly hard; water in the 3.5-7 gpg range is considered to be moderately hard; at 7.0-10.5 gpg water is considered to be hard; water greater than 10.5 gpg is considered very hard water. On the other hand, soft water contains less than 1 gpg.
Even if your customers have hard water, they may not know there's a problem since it is difficult to see or taste any difference between hard and soft water. But there's no doubt there's a difference when it comes to cleaning with even moderately hard water.
Effects On CleaningAll water-based cleaning and washing is less effective and less efficient with hard water. Cleaning with hard water requires greater physical effort and the use of greater quantities of cleaning agents for surfaces such as floors, sinks and bathtubs. It also leads to spotting on dishes and glassware.
Let's take a further look at one common job around the house: washing clothes.
Hardness minerals affect laundry in a gradual manner that tends to get hidden in today's automated washing process. People accustomed to washing in hard water may not notice the increased detergent use, yet the waste is still there. Soap was the primary cleaning agent for laundry before the development of synthetic detergents. Soap is usually made from natural fatty acids and alkali substances, such as caustic soda, which give it excellent cleaning properties. This is particularly true with vegetable-based fabrics like cotton.
Soap works well to suspend dirt in the wash and helps “lubricate” the fabric, prolonging its life. Unfortunately, hardness minerals combine with soap to produce insoluble “curds” which remain as a residue on washed laundry and in washing machines, and also tend to counteract soap's alkalinity. Even additives designed to overcome this problem tend to be less than effective.
Most modern detergents also contain additives to increase the alkalinity, but unfortunately, the builders tend to be consumed when the detergent needs to soften hard water. This limits their ability to clean and requires the use of greater quantities of detergent. The latest generation of concentrated liquid detergent does somewhat compensate for this.
Hard water also influences fabric life and fading, according to a 1991 Purdue University study. The study indicated that fabrics washed in hard water tend to wear out up to 15 percent quicker than fabrics washed in soft water. This is probably due to the presence of hardness residues in the fabric, making it stiffer and more brittle, leading to increased friction and wear as the fabric flexes.
The Purdue study also found that hard water generally has a negative effect on colors and whites. Colors were found to fade and whites to darken more quickly in hard water. In addition, the study found that laundry washed in hard water became resoiled with greater ease.
Soft Water SolutionsSoftening hard water typically involves the use of an ion exchange water softener. A typical water softener works on the principal of “cation exchange” in which the ions of hardness minerals (an ion is an electrically charged atom or group of atoms) are exchanged for sodium ions, effectively reducing the concentration of hardness minerals to insignificant levels.
As the water enters the softener, it passes over a resin bed in a special tank. The resin is made up of tiny inert beads of styrene and divinylbenzene that attract and hold sodium or potassium ions. The beads will exchange these ions whenever they encounter another ion such as calcium or magnesium.
After a period of use, the sodium or potassium ions are completely exchanged and the unit has to be “backwashed” or “regenerated,” which recharges the resin beads with sodium or potassium ions. This requires the use of sodium or potassium chloride, which is loaded into a “brine tank” where it dissolves in water, forming a brine used to recharge the system.
The recharging is generally done by one of two common methods: Automatic softeners initiate the process on a set time cycle according to anticipated need, and the demand initiated regeneration process which uses a meter or sensor to monitor the actual hardness levels or the amount of water the unit has processed.
A note for people concerned about the presence of sodium ions in their water: Use of sodium ions does not make the water noticeably salty or cause a significant increase in a person's sodium intake. In fact, the U.S. Food and Drug Administration defines water that would result from softening 75 gpg hard water - where much more sodium ions would have to be exchanged than is typically the case - as a “low sodium” beverage.
Whatever type of system is used, the applications can be quite affordable and highly worthwhile for those in hard water areas. A typical household water softener costs around $1,000 to $2,000, with a monthly operating expense of around $2 to $10 if sodium is used.
Hard water can cost your customers hundreds of dollars each year as it affects laundry operations, water heater efficiency, household cleaning and the life expectancy of plumbing fixtures and appliances. When it all adds up, hard water is a waste that can be done without. The solution to these problems is as easy as installing a water softener.
Hard water will be a key element of “Basic Water Treatment,” part of the WQA Aquatech USA 2006, March 28-April 1 in Rosemont, Ill. The seminar will include an overview of fundamentals for water-treatment professionals, as well as point-of-use/point-of-entry treatment technology including cation exchange water softening, residential reverse osmosis, filtration, carbon adsorption and deionization. For more information, visit www.wqa.org.