Does Reverse Osmosis Remove Salt?

Does reverse osmosis remove salt_RO filtration home water treatment for salt and sodium

The body requires a small amount of sodium to properly function, however, a recent study revealed that over 90% of Americans are consuming too much sodium[1]

Since reverse osmosis is one of the most popular water treatment systems, it begs the question: does reverse osmosis remove salt from drinking water? Yes, it does! 

Whether it comes from your water softener or other natural sources, too much sodium in your diet is a bad thing. Stay tuned to see why RO filtration is the most practical in-home solution for removing salt.

How Does Reverse Osmosis Remove Salt From Water?

Reverse osmosis works by forcing water through a semipermeable membrane that consists of very small pores to filter contaminants while letting only pure H2O molecules pass through [2]

The membrane pores are only 0.0001 micron, which is small enough to remove most water impurities, including dissolved salts. Over time it is necessary for the system to flush away the captured contaminants, which generates a small amount of waste water to cleanse the system.

Does Reverse Osmosis Remove Salt From Water_Reverse Osmosis Sodium Treatment Process Diagram Infographic

A typical reverse osmosis filtration system will consist of multiple stages.  For example, a 3-stage system will have the following steps:

  1. Sediment Filter: Removes large debris, sand, and dirt particles
  2. Semipermeable Membrane: Removes heavy metals, sodium, fluoride, PFAS, and much more.
  3. Carbon-Post Filter: Removes any remaining impurities and finishes the water to get rid of bad taste and odors. 

Reverse osmosis is a natural and highly effective method to remove sodium from drinking water.

How Much Salt Does Reverse Osmosis Remove?

The reverse osmosis process is capable of removing over 99% of dissolved salts and other common types of chemical contaminants from water [3]

When rock salt or table salt dissolves in water, it forms chloride and sodium. Chloride and sodium can both naturally occur in groundwater. However, increased levels can occur from water softeners, road salt, natural salt deposits, and sewage runoff [4]

The semipermeable membrane used in the reverse osmosis process is effective in trapping sodium ions and other contaminants where it is then rinsed clean and the brine water is drained away. 

In fact, because it is so effective at separating salt from water, reverse osmosis is widely used for the desalination process where dissolved salt concentration in seawater is reduced to a usable level [5].

What Other Contaminants Does Reverse Osmosis Remove? 

Reverse osmosis is not only effective at treating sodium but also a host of other common chemical contaminants:

How Can You Test For Sodium In Drinking Water?

If you want to know if there is too much sodium in your drinking water you have two options: 

Lab Test Your Home’s Water 

The only way to know for sure if sodium levels are too high in your water is with a home water test. To get the most robust and accurate results, a lab test kit from Tap Score is the best solution. The company tests for more than 100 contaminants in water. You simply collect a sample using the kit and send it back to a certified laboratory to test your water. 

Check The Local Water Quality Report

To check the water quality in your area, you can visit the Consumer Confidence Reports database. Since the EPA requires all local water suppliers to generate an annual local water quality report for consumer transparency, this will have data on a number of contaminants in your local water. 

Although this method is quick and easy, it doesn’t give you precise data for your home. The best solution is to get a home test kit as there are a wide variety of things that can affect each individual home.

How Does Salt Get Into Drinking Water?

Sodium and chloride levels in freshwater sources throughout the United States are quickly approaching unsustainable levels. 

“Chloride concentrations are increasing at a rate that threatens the availability of fresh water in the northeastern United States.”

National Academy Of Sciences Study

Salt gets into our drinking water through a variety of natural and unnatural methods. Here are the biggest contributors to the salt content in our water [6]

  • Road salts used for deicer 
  • Acid rain that erodes limestone and concrete
  • Sewage runoff 
  • Fertilizers using potassium salts
  • Mining operations disrupting various salt ion deposits
  • Water softener ion exchange process

Can Reverse Osmosis Be Used With A Water Softener?

Reverse osmosis systems can be used with water softeners since they are the most effective in-home treatment method to remove salt from water.

With traditional salt-based water softeners, sodium plays an important role.  A water softener removes hard water causing minerals like calcium and magnesium and replaces them with sodium ions.  As part of that process, a small amount of sodium is released into the water supply. 

This is why most homeowners who utilize a salt-based water softener also use a reverse osmosis system to get rid of the excess sodium that’s been added to their water in the water softening process.

Ion Exchange Process For Water Softeners

Unfortunately, the ion exchange process that’s used in water softeners adds sodium to the water [7].  

Traditional water softeners consist of two tanks, one tank for the resin beads and one brine tank for the salt. The resin tank has small beads with sodium ions attached. As hard water passes through the resin tank, the negatively charged minerals are exchanged with the sodium ions to create soft water. That water then flows throughout the home’s water supply. 

In the ion exchange process, the resin beads eventually become saturated with minerals and cannot effectively soften the water. It is then necessary to flush the softener with a brine solution to cleanse it and recharge the sodium ions.  The brine water is drained away and the process is ready to begin again. 

How Much Salt Does a Water Softener Add To Water

The amount of sodium added to water in the softening process will depend on the hardness of the water, but in general, 12.5 milligrams of sodium is added per 8-ounce glass

To calculate the sodium concentration in your water, you will need to start with the hardness of your water expressed in grains per gallon (GPG). Then multiply that number by 8 to see how many milligrams per liter of sodium is in your water. 

To be clear, the water processed by salt-based softeners contains sodium Na, not sodium chloride NaCl which is common table salt

Is Sodium In Water Bad For You?

Consuming water with high levels of sodium can have negative health consequences, especially for those with hypertension or high blood pressure. 

High sodium ion content in water can have different effects on the body depending on your current health condition:

  • Dehydration
  • Nausea 
  • High blood pressure
  • Heart disease 
  • Stroke

Although there is no sodium standard for drinking water, according to state and federal agencies, sodium levels in water should not exceed 20mg/L for those on very low sodium diets and 270 mg/L for those on more moderate sodium diets.  Additionally, the Food And Drug Administration has set the acceptable daily value for sodium at less than 2,300 milligrams per day [8].

Alternative Treatment Methods For Sodium In Drinking Water?

Aside from using reverse osmosis to remove sodium in drinking water, you can also use these alternative methods:

Activated Carbon Filtration

Activated charcoal filtration is used a lot in under-sink water filtration systems and water pitchers since they help filter out chlorine and other VOCs to produce safe drinking water. However, activated carbon isn’t capable of removing all types of contaminants including sodium that can easily slip through its filters. 

Water Distillation

Distillation is the process of heating water to its boiling point and condensing the vapor back to liquid form where it leaves behind impurities. Water distillation is extremely effective at removing up to 99.99% salt and other contaminants in water.

The downside to water distillation vs reverse osmosis is the distilling process is very time-consuming. However, since it is a natural process, you can make distilled water at home for free!

Salt-free Water Softener

Since traditional water softeners use a lot of sodium to treat water hardness, there are now salt-free water softeners that can tackle the problem. If the primary source of sodium in your water is a salt-based softener, choosing a salt-free alternative will rid your water of lingering sodium and neutralize scale at the same time.

Electronic Water Descaler

Another water softener alternative, electronic descalers reduce limescale formation that could cause harm to your appliances and fixtures. They are easy to install and are a smart alternative to traditional salt-based softeners.

FAQs For Reverse Osmosis Salt Removal

What’s the best way to remove salt from softened water?

A traditional water softener may solve the problem of water hardness, but it can also add salt to your water. Since excessive sodium in the diet can have negative health impacts, it’s best to invest in a reverse osmosis filter to be used in combination with your water softener to get rid of the excess salt before the water hits your tap.

Does reverse osmosis remove calcium and magnesium?

According to the CDC, a good reverse osmosis filtration system is capable of removing chemical contaminants such as sodium, chromium, lead, and chloride. However, it can only reduce the amount of calcium, magnesium, nitrate, potassium, and other elements in your drinking water. 

What are the disadvantages of using reverse osmosis and water softener together?

Although the use of a reverse osmosis filtration system and water softener is recommended, especially if you have problems with hard water, using both can get expensive.

Wastewater can also get quite high for both of these machines, so you can expect your water bills to be slightly higher than usual. 

What is not removed by reverse osmosis?

Reverse osmosis is considered one of the most effective water treatment options out there, but it doesn’t remove everything from your water. RO systems cannot remove some bacterial microorganisms and dissolved gases. 

Article Sources

Freshnss uses only the highest-quality sources to support the facts used in our articles including: government organizations, independent studies, peer-reviewed journals, and lab testing results. Read our editorial review guidelines here to learn more about how we verify and fact-check our writing to keep our content reliable, accurate, and trustworthy.

  1. Prevalence of Excess Sodium Intake in the United States, Centers For Disease Control And Prevention
  2. Point-Of-Use Reverse Osmosis Systems, Environmental Protection Agency (EPA)
  3. A Guide to Drinking Water Treatment Technologies for Household Use, Centers For Disease Control And Prevention
  4. Salt And Sodium, Harvard School Of Public Health
  5. Desalination By Reverse Osmosis, Organization of American States Secretariat for Political Affairs
  6. Salt And Drinking Water, New York State Department Of Health
  7. Drinking Water Treatment: Water Softening (Ion Exchange), University Of Nebraska – Lincoln
  8. Sodium in Your Diet: Use the Nutrition Facts Label and Reduce Your Intake, U.S. Food And Drug Administration
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