How A Water Softener Works

Water quality problems can be frustrating and daunting. From city water to well water, Central Indiana has some of the worst water quality in the United States. One of the biggest problems we run into is extremely hard water. Let us help you understand why.

Hard water scale is defined as dissolved calcium, lime, and magnesium. Indiana has some of the hardest water in the world. The state is known globally for Bedford Limestone, which practically covers many buildings and monuments in Washington, D.C. Here in Indiana, we are basically sitting on one of the largest limestone deposits on Earth.

Limestone is great for filtering water. It is porous and soft, meaning it can filter contaminants very effectively. However, this comes with some adverse effects. Water easily dissolves the limestone, becoming extremely hard. This is the buildup you see on faucets, shower doors, and especially in your water heater. Hard water causes all sorts of problems with your plumbing system and fixtures.

Some people try to use canister filters and so-called "water conditioning" systems. These do nothing to remove dissolved scale in your water. Imagine trying to remove dissolved sugar from water by running it through a filter—you would still have sugar water after the filter. Dissolved hard scale behaves in a similar way: it cannot be filtered by regular means. This is where a water softener comes in.

A water softener works by using ionic particle exchange (static charged particles). Calcium, lime, and magnesium are all positively charged at the molecular level. The filter media inside the softener is negatively charged. As hard water flows through the softener’s filter media, the positively charged particles (hard scale) stick to the negatively charged media, like a magnet.

Once the filter media is full of scale, the softener regenerates. The first step in the regeneration process is a backwash, where water flows in reverse through the filter, lifting and loosening the media. The second step is the salt brine process. Dissolved salt (sodium) in brine, which carries a negative charge, flows through the filter. These salt particles have slightly more charge than the filter media, causing the hard scale to break free from the media and attach to the salt particles.

The third step is the fast rinse, which flushes all the salt and hard scale down the drain, cleaning the media. The final step is the brine tank refill. Fresh water flows into the brine tank to dissolve more salt for the next regeneration.

A lot of people have misconceptions about softeners and low-sodium diets. If your softener is working properly, you should not be getting more than trace amounts of sodium in your water, if any at all. Another misconception is that soft water will kill plants or grass. Again, if the softener is functioning correctly, it will not harm your plants.

One final misconception I hear often is: “I got a softener to remove the rust from my water.” Softeners are not designed to remove iron. Using a softener for iron can trap it inside, dramatically shortening the softener’s lifespan. Salts with oxidizers (iron-remover salts) can help, but they never fully remove all the iron. Dissolved iron can still pass through at high concentrations, leaving yellowing in laundry and frustrating stains on fixtures.

In the next blog, we will discuss how an iron filter works.