Why Is Potassium Chloride Used in Water?

Potassium chloride is a salt that is used to remove minerals from hard water.

Water testing is a procedure used to identify various water problems, some of which may present serious health risks. Others, though not life threatening, are a nuisance and must be addressed. Hard water is an example of the latter. The term "hard" refers to water with high mineral content, particularly the minerals calcium and magnesium. Potassium chloride or sodium chloride (table salt) are compounds commonly used to remove excess minerals from water, a process called water softening.

Hard Water

Water that falls from the sky as rain, ice or snow is naturally soft. As the water flows through the ground and over soft rock, like limestone, it picks up minerals such as calcium and magnesium. The minerals remain dissolved in the groundwater that is then used for drinking, bathing, cooking and cleaning. Hard water can cause scale buildup within water pipes and all appliances through which it flows. It also results in soap scum, which adheres to bathroom fixtures and washed clothes, hair and skin.

Potassium and Sodium

Potassium chloride, like sodium chloride, is a salt that is soluble in water. When placed in water, potassium chloride and sodium chloride dissociate to yield charged particles called ions. Potassium and sodium ions have positive charges. The calcium and magnesium found in hard water are also present in the form of ions that are positively charged. The fact that all four elements exist as positive ions in solution led scientists to develop a method, called ion exchange, by which the hard minerals can be removed from the water and replaced with either potassium or sodium.

Ion Exchange

The most common method for softening hard water utilizes the process of ion exchange. During this process, water is diverted into a tank containing a resin that is coated with either potassium or sodium. As the hard water flows through the resin, the potassium or sodium on the resin and the calcium and magnesium in the water switch places. When the resin becomes saturated with calcium and magnesium, it is rinsed with a fresh salt solution to remove the hard minerals and replace the lost potassium or sodium.

Potassium Chloride Advantages

Potassium chloride or sodium chloride may be used to soften water. Since the ion exchange process results in the addition of either potassium or sodium to the water you are going to drink and otherwise use on a daily basis, the salt chosen for softening needs to be considered. Potassium chloride is recommended for individuals on sodium-restricted diets and those who are concerned in general about excess sodium intake. Potassium is also beneficial for watering plants since they require high levels of potassium to thrive. Too much sodium, on the other hand, causes plants to wilt and die.

Potassium Chloride Disadvantages

The major disadvantage of using potassium chloride rather than sodium chloride to soften water is its cost. A 40-pound bag of potassium chloride costs approximately twice as much as an equal weight of sodium chloride. Like sodium, excess potassium can be problematic for some individuals, including those taking certain medications or those with blood levels of potassium that are already abnormally high. When in doubt, consult your health care provider as to which water softening agent is best for you.

References

• "Cornell University Cooperative Extension-Water Bulletin: Hard Water"
• "Oak Ridge Associated Universities: Potassium Chloride Water Softener Salt"
• "University of Wisconsin Stevens Point: An Alternative to Softening with Sodium"

Resources

• "University of Nebraska-Lincoln: Water Softening (Ion Exchange)"