How an Ion-Exchange Water Softener Works

How an Ion-Exchange Water Softener Works

It seems like professionals in every field are giving us advice about what we should be doing, but this advice isn’t always easy to follow. Dentists tell us to floss twice a day and doctors tell us to exercise five times a week and eat balanced meals, and this is solid advice even if we usually fall short. Well, the advice doesn’t only come from medical professionals; plumbers are known to give advice as well. If you visit in Brooklyn, or talk to any local plumber, you will likely be told that if you have hard water, you should invest in a water softener to protect your plumbing. Unfortunately, few people know the differences between hard and soft water, let alone how a water softener works.

Types of Water Softeners

There are a few main types of water softeners available, but they all are said to decrease the impact of hard water. Hard water means that there are unwanted ions in your water that can lead to lime scale buildup in your pipes, scale buildup on your fixtures, and increased soap usage. Each type of water softener attempts to treat hard water in a different way. A descaler, or salt-free water softener, applies an electrical charge to ions which prevents them from causing problems. Magnetic water softeners claim to use magnets to change the properties of the water, though their actual effectiveness is hotly contested. Finally, the most popular and comprehensive solution to hard water is an ion-exchange water heater.  

Ion Replacement

Ion-exchange systems use salt to replace the unwanted ions in the water. As hard water passes through the softener, it goes through resin beads that contain plenty of sodium ions (salt). The magnesium, calcium, and other positively charged ions in the water will be attracted to the negative charge of the resin, and will swap places with the salt. This will add more salt content to the water, but salt is harmless compared to the alternative. The harder the water, the greater number of sodium ions added to the water supply.


Eventually, all of the sodium ions in the resin will have been replaced, and the water softener will need to regenerate, or dump away the collected magnesium and calcium ions and prepare the resin for future softening. Sodium chloride or sodium hydroxide is used to flush away the unwanted ions into the sewer. As long as the water softener has a supply of salt, it can soften water indefinitely.


If you’re considering an ion-exchange water softener, you now understand what it entails. You’ll have to purchase salt and keep it on hand, but in exchange you’ll get soft water that will be kind to you and your plumbing.

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