The Ins and Outs of How a Water Softener Works

Ginny Bartolone
Written by Ginny Bartolone
Updated October 5, 2021
Father with son in baby carrier doing laundry
Ariel Skelley/DigitalVision via Getty Images

Water softeners remove the calcium and magnesium buildup in your water with basic chemistry and some occasional maintenance

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Stubborn white spots on your dishes, stiff and dry hair, and that unsightly buildup on the end of your showerhead—all of these are common signs of the dreaded hard water. Water softeners have the ability to transform your home, affecting everything from the longevity of your appliances to the coziness of your favorite fall sweater. But how exactly does a water softener work, and how do you keep it running smoothly?

What Is Hard Water?

Everything from shampoo to clothing detergent brands throw around the term "hard water" and the threat it poses to your hair, clothing, bedding, and dishes. But what exactly is hard water? The term references the mineral-rich residue left behind from water with high levels of calcium and magnesium.

Understanding hard water and water softeners requires a bit of science, so put on your high school chemistry cap for a moment. Government agencies define hard water by the milligrams per liter (mg/L) of calcium carbonate. Here's how it breaks down:

  • Soft water: 0–60 mg/L

  • Moderately hard water: 61–120 mg/L

  • Hard water: 121–180 mg/L

  • Very hard water: More than 180 mg/L

Signs of Hard Water

You'll notice the effects of hard water even without running a home or mail-in test. Hard water can pop up in a range of ways:

  • Slimy feeling after washing your hands with soap

  • Buildup on the end of your faucets, showerheads, and hoses

  • Dry hair and skin

  • Stiff and scratchy laundry

  • Water spots on your dishes, especially after running through the dishwasher

  • Poorly functioning appliances

  • Issues with your hot water heater

Softening your water—aka removing the high levels of calcium and magnesium—can prolong the life of your water-based appliances, improve your hair, skin, and clothing, and even increase water heater efficiency.

What Is a Water Softener?

A water softener is an appliance that replaces the high levels of calcium and magnesium in water with "softer" minerals like potassium or sodium. Water softener installation typically costs between $500 and $6,000 depending on the type and size you choose.

The most common water softener features either one or two tanks and attaches to your main water source, either in the basement or just outside your house.

Through a bit of complex science that we'll jump into below, the soft water system pulls the hard minerals out of the water and replaces them with the softer ones before sending them on their merry way to the water heater and your pipes.

The Path of Water Through a Softener

Filling bottle with water from faucet
Dougal Waters/DigitalVision via Getty Images

Let's go on a journey with your home's water through a typical salt-based softener. When the water first enters your home, it makes a pit stop through a tank filled with negatively charged plastic resin beads. These beads are covered in positively charged sodium ions, or potassium in the case of a potassium water softener.

Since we all know that opposites attract, here's where things get clever. The negative beads attract positively charged magnesium and calcium passing by in the water. Sodium ions then switch out with the hard minerals and release into the water to balance the positive charge. In other words, calcium and magnesium stay in the tank, sodium and potassium carry on.

On a regular basis—typically during a time of low water use—the brine tank will flush the beads with salt water, taking the magnesium and calcium with it and down the drain. This also replaces the beads with sodium ions to start the process over.

Types of Water Softeners

You'll find some helpful variations of water softeners, both in size and the type of science they use to bump out those pesky hard minerals. For example:

  • Dual-tank salt water softeners: Two tanks allow the system to replenish itself without interrupting the flow of soft water to your home.

  • Salt-free system: Uses potassium-chloride instead of sodium, meaning you don't have to replenish the salt. The system works the same way as the sodium softener, but with potassium instead.

  • Water conditioners: These conditioners descale water, instead of simply removing hardening minerals, to protect against appliance and pipe buildup. While they do not technically count as a water softener, they tend to soften it in the process anyway.

Maintaining a Healthy Water Softener

Every model of water softener will come with unique instructions on how to keep it running nicely. Salt-based softeners require ongoing salt replacement, typically on a quarterly basis or every two months depending on the size and model of the system, how much water you use, and the hardness of your water.

On occasion, you may need to call a water softener specialist to take a look if:

  • you notice the signs of hard water on your skin, clothing, dishes, or appliances.

  • your hot water heater and appliances are not running as efficiently.

  • you've noticed buildup forming again on your faucets or showerhead.

In these cases, your water softener could be low on salt. It may also be having issues regularly replenishing itself or even have a leak. Water softener repairs typically cost anywhere between $150 and $735.

For a set-it-and-forget-it maintenance method, many experts encourage scheduling regular check-ins with your water softener pro. Companies may offer bi-monthly or quarterly visits for a flat rate each year to make sure everything is working well.

Water softeners can prolong the life of your appliances and even improve overall performance. Your skin and hair may feel a bit softer, sheets much cozier to the touch, and water a bit warmer. The investment and basic upkeep are all it takes to keep your water running as smoothly as possible.

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