Water softening (to create soft water) is the reduction or removal of calcium and magnesium cations (positively charged ions) which are the principal cause of hardness in water (hard water). The most commonly used method to reduce or remove calcium and magnesium is the cation exchange resin system.
What is Hard Water?
Eighty-five percent of the United States has water that is hard enough to require softening. The chemistry of hard water is not complicated, it is simply an abundance of calcium (Ca) and magnesium (Mg) – often called “hardness minerals” – dissolved in water.
In contrast rainfall is naturally soft water but it does not stay soft for long; as the rain falls on the earth it seeps through soil and rock which is loaded with hardness minerals.
The rainwater soon turns from soft to hard. The level of hardness depends on the make-up of the rock in your water catchment area.
All rock minerals have an electrical charge, both the hardness minerals Ca and Mg are positively charged, this an important part in understanding how a water softener works.
Why should I be concerned about hard water?
Hard water is expensive and there are two reasons: Soap curd and scale formation. When Ca and Mg react with soap and detergents soap curds are formed, these curds form a layer over fabrics dulling colors and making whites look gray. Curds also make individual fibers brittle which shortens the life of the fabric and your garments.
Because your detergent combines with the hardness minerals you will have to use more detergent to make soap suds.
The other more serious problem is scale. Scale is formed as hard water is heated. As the water heats the hardness minerals are deposited in warm water pipes, water heaters, appliances and boilers.
If left to build up the scale can become as hard as rock. The result is that the heating element has to heat the rock as well as the water, using a lot more energy.
How do I know if I have hard water?
Are your sinks, toilets, tubs, dishes and glassware marked with water stains? Is your hot water kettle always full of “fur”? Do your clothes look dull? If you answered “Yes” then you probably have hard water.
If you want to be more accurate you can do a home hardness test or you could call your municipal water department and ask them to recommend an independent water testing laboratory who will tell you your exact water hardness in “Grains per Gallon” (GPG). You can use the result to calculate the size water softener you need for your household.
How can I do a home hardness test?
Take a screw top jar and some pure detergent or bar soap. Half fill the jar with cold tap water. Next sprinkle a few flakes of detergent, or scrape a few shavings of bar soap in to the water. Place the lid on the jar and shake until a lather or foam forms. If there is little or no lather your water is considered hard. Next dip your finger into the water. Did it leave soap curd on your finger? If it did you probably have hard water.
How does a water softener work?
There are several ways to reduce water hardness: Chemical additives, deionzation, distillation, reverse osmosis and cation resin exchange. The most common method for point-of-entry (POE) treatment and the one recommended by Fresh Water Systems is cation exchange.
A cation is a positively charged ion, both the hardness minerals calcium (Ca) and magnesium (Mg) are cations. To remove them from water the hardness cations are exchanged with sodium ions (also a cation).
What size water softener do I need?
The answer depends on the amount of water hardness passing through your home or office per day. Hardness is measured in grains per gallon and water softener capacities are given in terms of the number of grains of hardness they will remove between regenerations. (Also termed resin capacity). There are some simple calculations to do.
First of all you need to calculate how much water your household uses: Multiply the number of people in your household by 75 (the average number of gallons of water used per person per day).
Then find out the GPG hardness of your water (20 GPG is common in most hard water areas). Multiply the water usage by the GPG. So, for a 4-person household living in an area with a GPG of 20: 4 x 75 = 300, then 300 x 20 = 6,000 GPG total hardness per day.
A typical household softener’s capacity is 20,000-30,000 grains. It’s recommended that a softener has enough capacity to last three days between regenerations. Using the 4-person household example again, over 3 days, 18,000 grains would be passed through a softener. Therefore a softener with a 20,000 resin capacity would meet your needs.
Is the sodium added to my water during cation exchange a health risk?
For some consumers, the fact that sodium is used to soften water raises a concern about their drinking water and a potential health risk. However, what many people may not know is that when doctors and researchers discuss salt and its effects on a person’s health, they usually refer to sodium chloride, and not sodium bicarbonate which is the result of softening. However, sodium-free alternatives are available for Fresh Water System’s customers.
Further, according to Dr. Andrew Zeifer, Director of the Hypertension Clinic at the University of Michigan, “Drinking water represents a very small part of sodium intake in most persons. Even water softening systems using salt don’t introduce enough salt to be of concern.”
Similar views were expressed in the New England Journal of Medicine, and by the U.S. >Environmental Protection Agency (EPA). Information From Water Quality Association.