Water Softeners: How Do They Work?

Kenneth Wilson

Water softening is a chemical process to reduce dissolved minerals in our water to prevent scale formation in our household appliances and on surfaces. The dissolved ions are precipitated with chemicals and separated from the water. A water softening device is designed to facilitate this process.

Negatively charged microscopic resin beads are used as a filter medium capturing the positively charged calcium and magnesium ions in the water. The softened water passes through the system for use in the house, containing a much lower calcium and magnesium ion content.

The calcium and magnesium deposits buildup on the resin beads must occasionally be chemically scrubbed off for the water softener to remain effective. Let's look at how water softeners are designed to provide you with water with the optimal content of dissolved minerals.

Why Does Water Need to be Softened?

Pure water is very rare in nature. Water is the best solvent on earth as it consists of a polar molecule consisting of two hydrogen atoms bonded to an oxygen atom in a non-linear molecule. The angle between the hydrogen and oxygen bonds is 104.45 degrees, making one side of the water molecule slightly more positive and slightly more negative.

This "polarity" of the water molecule makes it an easy molecule to attract other charged ions to form bonds. Pure water is corrosive and can dissolve the calcium from your teeth and bones if you drink it. This corrosiveness is why we cannot drink pure distilled water. Highly purified water must be treated with mineral salts to make it safe for us to drink.

All freshwater contains soluble minerals such as calcium and magnesium carbonates. Rainwater is absorbed by the soil and drains into rivers or underground aquifers from where water utility companies draw it and treat it to eliminate biohazards from the water. The dissolved minerals are healthy for humans and help in creating bone mass density in our bodies.

Even when the raindrops are formed in the atmosphere, the water molecules will bond with molecules like carbon dioxide in the air to form weak carbolic acid. High levels of pollution can cause acid rain to form, as often happens in highly polluted cities. The acid rain will dissolve rocks and siphon into the ground or river system in a catchment area.

The dissolved minerals are critical to providing nutrients to plant and animal life. Depending on the type of rock and soil in an area, the amount of dissolved minerals in the area's water supply can be very high, resulting in hard water, generating foam lather when hard water and soap are mixed results in the formation of soap scum.

The formation of soap scum or scale deposits that can build up on the heating elements of appliances like kettles, steam irons, dishwashers, and washing machines is caused by hard water. Washing your skin and hair with hard water also makes the skin feel irritated and hair feel stiff and difficult to manage.

Some utility companies also add chemicals like fluoride and chloride during the chemical treatment of water before supplying the water to the household. Water softeners have been designed to strip some of the dissolved minerals and chemicals from the water before using them in a household.

The water softener consists of a chamber filled with small plastic beads with a negative charge and will attract and bind calcium and magnesium ions, which are positively charged. Other filters containing carbon will capture chlorine and dissolved organic compounds present in the water.

The resulting product water has a much-reduced level of dissolved minerals and will be cleaned of chlorine and organic contaminants. The water will taste and smell much better than untreated hard water. The buildup of ions on the plastic beads has to be occasionally cleaned off to maintain their ability to capture ions.

Coarse table salt (sodium chloride) is dissolved in water to form sodium and chloride ions which strip the built-up calcium and magnesium ions from the plastic beads to form very stable molecules that will precipitate out of the water. Once the plastic beads have been regenerated, they can once again act to soften the incoming water.

Is Softened Water Safe to Drink?

A water softener is one of the recommended water filtering and treatment devices for improving water quality. (Related: Home Water Softener System: Pricing, Cost Factors and More) The sodium chloride used to regenerate the plastic beads responsible for capturing the calcium and magnesium ions may cause higher sodium content in the softened water.

Sodium is not healthy for our bodies, and it is recommended that the water intended for drinking and cooking be purified by reverse osmosis. When cleaning the plastic beads with sodium chloride, take care to rinse them off very well and flush the system with fresh water to eliminate excess sodium chloride.

It is also recommended to install a carbon inline filter on the water line destined for drinking and cooking water. The advantage of water softeners is mainly to protect the heating elements in water heaters, kettles, irons, washing machines, and dishwashers and extend their useful life.

To ensure that softened water is safe to drink, it is recommended to be further purified and treated by reverse osmosis to eliminate excess sodium. (Related: How Much Does a Reverse Osmosis System Cost? (2022 Buying Guide)) The daily intake of sodium must be limited to less than 2,300 mg per day. We get this much sodium just from the salt in our food.


The dissolved mineral content in the water supplied for domestic consumption is often too high, leading to hard water. This water does not taste well and does not form a thick lather when mixed with soap. The hard water will cause mineral deposits to form inside the copper pipes of domestic appliances.

Water softeners are designed to let the excess calcium and magnesium minerals deposit on specially designed plastic beads. As the deposited minerals become too tick to allow the plastic beads to perform their function, they can be cleaned using sodium chloride to extract and precipitate the minerals.

The chemical deposition of the excess calcium and magnesium minerals will leave the water "soft" and it will easily foam up when used to wash clothes or wash your skin and hair. Softened water contains high levels of sodium which is not healthy living organisms.

Kenneth Wilson
November 30, 2021
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Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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