Back To Blog Page

How to Remove Salt from Water

If you have an ion-exchange water softening system you might be curious about how to remove salt from water. The soft water produced by ion-exchange systems contains a small amount of sodium. This small amount of sodium can’t be tasted, but some people prefer to remove sodium from their drinking water entirely. Understanding how to remove salts from water can help you determine whether augmenting your water softening system is right for you.

Soft Water and Sodium

Sodium plays a critical part in the water softening process. There are two primary ways that the impact of hard water is dealt with in a residential setting: water softeners and water conditioners. A water softener removes the mineral content of hard water and replaces it with a small number of sodium ions, while a water conditioner changes the minerals so they can’t cause scaling. Water conditioners are sometimes known as salt-free water softeners since the water conditioned by these systems doesn’t contain sodium. Learn the difference between a salt versus salt free water softener with our guide.

Water softeners function through a process known as ion-exchange. Sodium plays a critical role in this process.

Ion-Exchange

When water percolates through the soil and stone of Earth’s crust, it picks up mineral ions. These mineral ions, most often consisting of calcium and magnesium, bond to the water molecule. Once the water reaches your tap it has undergone a series of treatments, but those treatments don’t address the mineral content of the water.

Here is where an ion-exchange system comes in. These systems are usually installed where the main water line comes into your home after the water meter. These systems contain at least two tanks: a brine tank and a resin tank.

The resin tank contains small, negatively charged resin beads that have sodium ions attached to them. As hard water is piped into the resin tank and passes over the resin beads, the positively charged mineral ions attached to the water molecule are attracted to the negatively charged resin. When these mineral ions are drawn away from the water molecule they are replaced with the sodium ions which had previously been attached to the resin beads. The replacement of a positively charged mineral ion with a positively charged sodium ion allows the water molecule to retain an ionic balance.

Over time, the resin beads in the tank will have a large number of mineral ions attached to them. If these ions are not flushed from the system then eventually it will stop softening water. In order to flush the system, salty brine in the brine tank is flooded into the resin tank. The salty water displaces the mineral ions from the resin, replacing them once again with positively charged sodium ions. The brine solution containing the mineral ions is flushed from the system down the drain, and the system is ready to begin softening again.

The Impact of Sodium in Soft Water

Some people are skeptical about water softeners which use ion-exchange because of the sodium in the soft water they produce. This is understandable, particularly because the dangers of high-sodium diets have been discussed extensively over recent decades.

To clear up any confusion, the soft water produced by these systems contains sodium (Na) and not table salt, sodium chloride (NaCl). The sodium added to the water doesn’t alter the taste of the water. Still, it is worth considering the impact of this sodium. For the average, healthy adult the sodium content in soft water poses little risk. The exact sodium content of the water produced by your system will depend on how hard it is going into the system. Harder water going into a water softener will have more sodium coming out of the system. 

For example, water containing 10 grains-per-gallon (GPG) of calcium carbonate is considered very hard on the water hardness scale. Once softened this water will contain only 74 milligrams (mg) of sodium in a quart of water or 298 mg per gallon. To put this number in perspective, each gallon of soft water provides slightly more sodium than two slices of white bread or two cups of milk.

Removing Salt From Water

While the sodium content of softened water doesn’t pose a risk to most people, some individuals require low sodium in their diets or simply prefer the sodium removed from their drinking water. If you still want the benefits of softened water but don’t want sodium in your drinking water, you’ll need to understand how to remove salinity from water.

The most common and effective way to remove salt from water is through physical filtration. Specifically, reverse osmosis systems are capable of removing salt and a wide variety of other contaminants from softened water.

Let’s take a closer look at reverse osmosis systems, which offer a method for how to remove salt from water naturally.

Reverse Osmosis System

To understand reverse osmosis, it is helpful to start with osmosis. Osmosis is all around us and is important for how our bodies function. To understand osmosis, picture two liquids on either side of a membrane. Those liquids contain different amounts of dissolved substance. On one side of the membrane, the solution has a high concentration of the dissolved substance, while the solution on the other side has a low concentration of a dissolved substance. 

In osmosis, the liquid which has a low amount of the dissolved substance will flow across the membrane to the solution with a high amount of dissolved substances. This flow will continue until the liquid on both sides of the membrane contains an equal amount of liquid and dissolved substance. The force causing this flow is known as osmotic pressure.

Reverse osmosis is the exact opposite of this natural process. Desalination is the removal of salt from seawater and is an easy way to visualize reverse osmosis in action. When water is desalinated using reverse osmosis, saltwater is forced at high pressure across a semipermeable membrane. 

In order to force the water across the membrane, the pressure used in the system must exceed the osmotic pressure. The membrane used has pores large enough to allow water molecules through, but not large enough to allow sodium ions or many other contaminants through. The result on the other side of the membrane is freshwater that has had the vast majority of sodium removed.

Benefits of Reverse Osmosis

Reverse osmosis is a highly effective and natural method for removing sodium from softened water. At the same time, reverse osmosis systems also dramatically reduce the number of contaminants in water. 

Reverse osmosis systems are effective at removing or reducing:

  • Sodium
  • Nitrates
  • Mineral and metal ions
  • Bacteria (Salmonella)
  • Protozoa (Giardia)
  • Viruses (norovirus)
  • Perfluoroalkyl substances (PFAS)

Reverse osmosis systems may also contain a pre-filter to clear out any sediment and a post-filter consisting of activated carbon. Activated carbon filters are highly effective at removing many of the substances which give tap water a bad taste and smell. These include disinfectants like chlorine used in water treatment, chloramines, and volatile organic chemicals (VOCs). By using a reverse osmosis system that incorporates activated carbon filtration, you’ll be sure your drinking water has fewer contaminants and a clean, filtered taste. See our guide to Does Water Have a Taste for more information.

Can You Use Both Systems?

Yes! You can use a water softener and reverse osmosis at the same time. Here’s how it works. Ion-exchange water softeners are installed as a point-of-entry (POE) system. What this means is ion-exchange systems are installed where the water line comes into the house, and are intended to provide soft water throughout the house.

If you are concerned about the sodium content of soft water, you’ll install a reverse osmosis system at the point-of-use (POU). This may be at your kitchen sink or wherever you prefer to pour your drinking water.

With this type of dual system setup, hard water enters your house and immediately enters the water softening system where mineral ions are exchanged with sodium ions. This water is then piped throughout your home. Before it hits the tap where you want to provide drinking water the soft water enters the reverse osmosis system. Here any sodium ions are removed, as well as a broad array of other contaminants. 

Using both systems in this way allows you to have the benefits of both soft water and water filtration. Softening your water ensures you won’t have to deal with the soap scum, scaling, and deposits that come with hard water. Water filtration using reverse osmosis gives you gallons of filtered, clean water.

Final Thoughts

Most people aren’t negatively affected by the sodium content of softened water, but it is important to recognize the options available to remove the salt from softened water or go with one of the best salt free water systems. The most common solution is to install a reverse-osmosis system to provide filtered, clean water. 

The benefit of this solution is that not only will sodium be removed from your drinking water, but you’ll also have peace of mind knowing many other contaminants will be removed as well. These include microbes like giardia and salmonella, nitrates, and PFAS.

To learn more about water softener alternatives and options for removing salt from your freshwater, please contact Rayne Water today.

Sources:

  1. https://academic-eb-com.prox.miracosta.edu/levels/collegiate/article/hard-water/39219
  2. https://www.usgs.gov/special-topic/water-science-school/science/hardness-water?qt-science_center_objects=0#qt-science_center_objects
  3. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/sodium/how-much-sodium-should-i-eat-per-day
  4. https://www.water-rightgroup.com/blog/myths-about-water-softeners-8-things-people-get-wrong/