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Does Reverse Osmosis Remove Calcium And Magnesium From Water?

Does Reverse Osmosis Remove Calcium And Magnesium


The latest technology has launched water treatment systems that can remove the concerns of impurities. Similarly, reverse osmosis water filters are one of them that incredibly works to remove minerals, salts, heavy metals, bacteria, viruses, and various others. It is renowned for its ability to provide crystal-clear water. 

Minerals can seep through the underground water along with other various contaminants which are necessary to remove. Their excess amount can cause various health issues, specifically aesthetic issues like white scales and deposits on fixtures. Reverse osmosis can leach 99% of impurities, including calcium, magnesium, sodium, fluoride, and iron, from water. 

In this guide, you’ll learn does a reverse osmosis filter removes minerals and how you can remineralize the RO water. Let’s start to get safe and clean water!

Does Reverse Osmosis Remove Minerals From Water? (CALCIUM AND MAGNESIUM) 

Reverse osmosis can easily remove minerals from water. It is a process in which a semi-permeable membrane removes every type of impurity, including minerals, resulting in “softened” water. This membrane acts as a barrier, allowing water molecules to pass through while blocking the dissolved solids such as calcium, magnesium, fluoride, etc.

The purified water, whose impurities are removed, can be collected through the faucet. In contrast, the rejected contaminants, often referred to as “brine” or “reject water,” are sent down a separate drain.

In summary, reverse osmosis is an efficient method for leaching minerals from water. However, it is not specifically designed to remove the hardness of the water. It can achieve a removal rate of up to 90-99%, depending on conditions like the quality of the RO membrane, high water pressure, high temperature, and the initial concentration of minerals and impurities in the water.

Common Minerals Found in Water—RO Can Remove Them

The most common minerals that reverse osmosis can remove from your well water are as follows.

1. Calcium (Ca)

Calcium is an essential element for bones, teeth, and muscles whose deficiency can lead to weakened bones, muscle cramps, and other health issues. You can take dietary calcium from dairy products, leafy green vegetables, nuts, and fortified foods, which is enough to keep you healthy and strong. 

Calcium enters well water primarily through the dissolution of calcium-containing minerals, such as limestone and gypsum, which add to the groundwater and seep through the well. The levels of calcium beyond 170 mg/L can cause various health and aesthetic effects.

When high levels of calcium are dissolved in water, it forms limescale and may precipitate out of the water as solid calcium carbonate. Notice if you’ve ever seen the formation of hard, chalky deposits on sinks, glass shower doors, mirrors, appliances, and plumbing fixtures. The reverse osmosis membrane filters the calcium molecules up to 90% and blocks them, allowing the filtered water to pass from it. 

2. Magnesium (Mg)

Like calcium, magnesium is also an important component of bone, muscle strength, and weight management. Its deficiency can cause muscle weakness, fatigue, and cardiovascular problems. You can get magnesium from foods such as whole grains, nuts, seeds, green leafy vegetables, and seafood.

Magnesium enters well water through the dissolution of magnesium-containing minerals, which seeps into the well. If your well water contains more than 50-100 mg/L of magnesium, it can make your water harder to give aesthetic effects, the same as calcium. 

For excess minerals like calcium and magnesium, reverse osmosis is an efficient system to remove up to 90%.

3. Sodium (Na⁺)

Sodium, commonly found in salt (sodium chloride), is crucial for maintaining essential bodily functions. It plays a vital role in regulating blood pressure, fluid balance, nerve function, muscle contractions, and the transmission of electrical signals in the body.

However, excessive sodium intake, either by drinking water or eating food, is often associated with health issues like hypertension and an increased risk of heart disease. Its deficiency is rare but can lead to muscle cramps. We can control the amount of salt in our diet, but what about the salt or sodium present in water?

Sodium can enter well water from geological sources or as a result of road salt runoff. The level of sodium in your well water should be less than 20 mg/L. If high sodium is your main concern, a reverse osmosis water filter system can perform 95% removal

4. Fluoride

Fluoride is essential for dental health, as it helps prevent tooth decay. If your body has an inadequate amount of fluoride, it can lead to an increased risk of dental cavities. Tea, some seafood, and, specifically, fluoridated water are the best sources. 

But fluoride has become one of the major issues in most areas of the U.S. where its high levels need to be controlled. It can naturally occur in groundwater or be added to water supplies for dental health. The safe levels of fluoride levels in drinking water typically range from 0.7 to 1.2 mg/L. 

Various specifically designed water filters can remove fluoride; out of them, reverse osmosis water is an ideal choice; however, it is not necessary where fluoridation is needed. 

5. Potassium (K⁺):

Potassium is crucial for heart health, muscle function, and nerve transmission. Its deficiency can lead to muscle weakness and irregular heart rhythms. You can eat potassium-rich foods such as bananas, potatoes, beans, and leafy greens to fulfill the dietary source.

In well water, there is no specific recommended safe level for potassium in drinking. However, like calcium and magnesium, reverse osmosis significantly reduces the potassium levels in water.

6. Iron (Fe²⁺/Fe³⁺)

Iron is an essential component of our body for transporting oxygen in the blood and overall energy production. Its deficiency can lead to anemia, fatigue, and impaired cognitive function. Its dietary sources include red meat, poultry, fish, beans, and fortified cereals. 

Iron can naturally occur in groundwater, often as ferrous (Fe²⁺) or ferric (Fe³⁺) ions. Ferrous is more toxic and difficult to remove rather than ferric iron. In well water, it should be 0.3 mg/L. When iron levels are elevated in the well, it may give a yellowish tint to the water. Additionally, you can notice the rusty stains on your sin, appliances, and plumbings. 

Reverse osmosis water filters are highly efficient in removing ferric iron, but ferrous iron needs to be oxidized first by using an oxidation media; later on, it can be filtered out. However, iron can clog the membrane, so we suggest using iron filters, which are specifically designed to remove it. 

How To Make RO Water Alkaline

how to make reverse osmosis water alkaline 01

If your reverse osmosis water filter has removed all the essential minerals along with rough impurities, how to remineralize it? It is very simple; we suggest using a remineralizing filter in conjunction with your RO (reverse osmosis) system is a practical and convenient way to make the water alkaline

Alternate, considering an alkaline water pitcher that contains minerals like calcium, magnesium, and potassium i the best option. You just need to fill the pitcher with your RO water and let it pass through the alkaline pitcher filter. Once it passes, it will be alkaline and ready to drink. 

You can also make the RO water alkaline naturally by using a few drops of lemon juice, baking soda, mineral drops, Himalayan salt, or sea salt. You can choose depending on your choice, availability, and budget. 

Most people want purified water but love the mineral crispness in the water, which you can restore by using an alkaline filter. This specialized filter is designed to add essential minerals such as calcium and magnesium back into the water, effectively counteracting the demineralization caused by the RO process. As a result, you can enjoy safe hydration!

Test the pH of Alkaline Water

How to Test Alkaline Water at Home

If you are done with remineralization, there is an option if you want to check the pH of alkaline water. For this purpose, you can use a pH testing kit or digital pH meter to aim for a pH between 7.5 and 8.5, which is considered alkaline. If you want to learn a detailed guide on checking the pH of alkaline water at home, click here.


So, yes, reverse osmosis water filters can filter out microorganisms, heavy metals, salts, and various others. Its semi-permeable membrane is designed to block the passage of large molecules like minerals, resulting in demineralized water.

While this mineral removal can be advantageous, such as improving the taste and reducing scale buildup in appliances, for most people, the mineral taste in water is considerable. 

By using either an alkaline filter or an alkaline water pitcher, you can easily raise the pH of your RO water to improve hydration and neutralization of acidity in the body.

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