Does Reverse Osmosis Remove Sodium from Softened Water? #Salt

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If you’re concerned about your water’s salt levels after using a water softener, you’re not alone. Many people are looking for ways to remove salt from their softened water.

Reverse osmosis is a popular filtration method, and it’s effective against many contaminants.

But does reverse osmosis remove salt from softened water, too? Let’s find out!

Key Takeaways

  • Yes, reverse osmosis removes salt from softened water.
  • And it does so very effectively. A home RO system can remove up to 99% of sodium present in soft water.

Does Reverse Osmosis Remove Sodium from Softened Water?

Yes, reverse osmosis removes sodium from softened water. In fact, RO removes salt, or sodium, from all types of water.

How Does RO Water Treatment Remove Sodium?

RO water treatment removes sodium from water the same way it removes other contaminants. Reverse osmosis works by pushing water under high pressure through a semipermeable membrane. The RO membrane has tiny pores that allow water molecules to pass through, but blocks contaminants like sodium and prevents them from mixing up with the filtered water.

The system flushes out the trapped sodium and other contaminants along with wastewater.

Bottom line: RO water treatment works for removing sodium, thanks to the tiny pores in the RO membrane.

Under Sink Reverse Osmosis System

How Much Sodium Can Be Removed?

Reverse osmosis removes up to 99% of sodium from water, so it’s highly effective and reliable.

More Contaminants That Reverse Osmosis Removes

Apart from sodium, reverse osmosis systems remove many other contaminants. These include:

  • Arsenic
  • Chromium
  • Fluoride
  • Lead
  • Bacteria like E.coli and Salmonella
  • Viruses
  • Protozoa like Giardia and Cryptosporidium
  • Sediments
  • Nitrates
  • Chlorine/chloramine and their disinfection byproducts
  • Pharmaceuticals
  • Pesticides

Other Ways to Remove Salt from Soft Water

If, for some reason, you choose not to use reverse osmosis to remove salt from your soft water, these other water treatment methods can serve as alternatives:

Ion Exchange (Deionization)

Deionization (also known as demineralization) is the process of removing mineral ions in water.

Deionizers use specially manufactured resin beads to replace the salt ions in water with harmless hydrogen ions. The ion exchange occurs as the water flows over the resin beads, and the water comes out sodium-free.


Distillation is another effective method of removing salt/sodium from water. During the process, water is boiled at a high temperature until it evaporates completely. The thing is, salt has a much higher boiling point than water. So while the water evaporates, the salt stays back in the boiling chamber.

The evaporated water goes into a separate section where it cools down and converts back to liquid. Then, it passes through a post-filter that blocks any leftover contaminants. The distilled, salt-free water gathers into a reservoir where you can use it.

Salt-Free Water Conditioners

Unlike traditional salt-based water softeners, salt-free water conditioners do not exchange hard minerals with salt, so they don’t add any sodium to your water.

In fact, they also don’t remove hardness minerals at all. Instead, they bind these minerals together, so they cannot cause issues to you or your plumbing. Using a salt-free water conditioner prevents salt from getting into your conditioned water in the first place.

Note: Salt-free conditioners may eliminate hard water problems, but they don’t really soften water. They only make the hardness minerals inactive so to speak. Some people have reservations about using them for this reason.

Potassium Chloride

An excellent alternative to salt-free conditioners are water softeners that use potassium chloride. Potassium chloride softeners replace hard minerals with potassium instead of sodium.

With this system, you can soften your water without risking any extra sodium.

The Water Softening Process: Where Does the Sodium Come from?

You may have noticed that your water’s salt level increases after it passes through the water softener in your home. But why is that? The reason has to do with how water softening works…

Water softening replaces hardness-causing ions (primarily calcium and magnesium) with sodium ions. Water softeners mainly consist of a resin tank, a brine tank, and a head valve.

  • The head valve operates the softener, directing its process and controlling the flow of water.
  • The resin tank contains microbeads that carry the sodium ions
  • And the brine tank stores salt.

When your water flows through the resin tank, the resin beads collect the hardness minerals present and replace them with sodium ions — this is called ion exchange.

After a while, the resin tank becomes full of hard minerals, and the sodium ions are depleted. Due to sodium ion shortage in the resin tank, the brine tank releases highly concentrated salt water to wash away the hard minerals on the resin and replenish its sodium ions.

salt-based water softener

Health Effects of Sodium in Softened Water

Unfortunately, sodium in water can have dire health effects. Consuming too much sodium can cause nausea, digestive tract inflammation, convulsions, and in serious cases, death.

However, for most healthy people, the amount of salt added by water softeners is negligible and will not cause any health issues. Just for people with high blood pressure and other medical conditions requiring a sodium-restricted diet, drinking softened water without filtering the sodium may cause the unpleasant health effects mentioned earlier.

If reducing your sodium intake is very important for medical reasons, removing sodium from your water is not the only thing to do. You should also:

  • Check the sodium content of your foods (you’ll find it on the nutrition facts label). If there’s a similar food with lower sodium content, opt for it.
  • Reduce your consumption of processed food and drinks in general. Prepare your meals yourself whenever possible.
  • Garnish your meals with ginger, onion powder, and garlic to reduce the salt you need to add.
  • Eat more fresh fruits and vegetables.

Why Water Softening and Reverse Osmosis Work Well Together

We’ve established that reverse osmosis removes salt from softened water, making it safer. That’s one crucial reason why water softening and reverse osmosis work well together — they complement each other to improve water quality. Softening plus reverse osmosis produces water that is both soft and free from salt and many other contaminants.

But there’s more!

If your water is hard and you use just a reverse osmosis system, there’s a high chance that the system will not last very long. This is because hard water leaves scale deposits on the RO membrane, clogging it and reducing its efficiency.

With a water softener and an RO system in combination, the softener removes hardness-causing minerals before the water reaches the RO membrane, protecting it from damage.

If you have any thoughts about the question, does reverse osmosis remove sodium from a water softener, please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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