January 06, 2023

What Is a Reverse Osmosis System?

By: Nathan Hawkes

What Is a Reverse Osmosis System?

If you're looking for a way to improve the quality and taste of your drinking water, there's no better option than a reverse osmosis water system. Reverse osmosis (RO) systems are designed to remove all chemicals and contaminants from your water, leaving you with a high-quality end-product that's perfect for drinking, cooking, using in aquariums and more.

Reverse osmosis is a water filtration process that uses pressure to force water through a semipermeable membrane, which removes dissolved solids, organics and other contaminants. This allows only clean water molecules to pass through, leaving the contaminants behind.

The purified water is then stored in a storage tank, ready for use.

Reverse osmosis systems are designed to remove up to 99% of contaminants from water, such as lead, arsenic, fluoride, nitrates and other dissolved solids. Reverse osmosis systems also reduce chlorine taste and odor, leaving your water clean and refreshing to drink.

Reverse osmosis systems are becoming increasingly popular, due to their effectiveness in purifying water and the ease of installation. Reverse osmosis systems are available in a variety of sizes and configurations to fit any size budget.

History of Reverse Osmosis Systems

Reverse osmosis systems have been in use since the 1960s, when they were first developed to desalinate seawater. During this time, reverse osmosis systems were relatively expensive and only used in industrial applications. Since then, reverse osmosis technology has been continually improved upon, making it more cost effective and efficient for home use.

The inventor of reverse osmosis technology, Dr. Sidney Loeb, along with Srinivasa Sourirajan, utilized semi-permeable anisotropic membranes—a technology that is still used in reverse osmosis systems today. The membrane allows only water molecules to pass through it while blocking other impurities and contaminants.

Dr. Sidney Loeb continued to innovate and refine reverse osmosis systems throughout his career. He eventually developed a system that could achieve up to 99% rejection of salt and other contaminants, making reverse osmosis systems an even more reliable water purification method for both residential and commercial settings.

Today, reverse osmosis systems are widely used in facilities such as hospitals and schools to provide clean drinking water. They are also used in food and beverage production, power plants and even some industrial processes. With such versatility and reliability, reverse osmosis systems are becoming increasingly popular as an eco-friendly and cost-effective method of water purification.

How Does Reverse Osmosis Work?

Most home RO systems are five-stage systems, meaning water passes through five different filters before the end-product is ready for consumption. These systems are installed under the kitchen sink, and they usually consist of a sediment filter, carbon and chlorine filter, reverse osmosis membrane (which is the primary filtration method) and a post-filter. Each of these filters has a specific purpose, from removing contaminants such as lead or chlorine to trapping microscopic particles like dust.

3 Pre-Filters

The following filters work to prolong the life of the “heart” of the system, the reverse osmosis membrane. 

Sediment Filter

Water first enters a sediment filter, where any large particles are removed. This removes rust, dirt, dust and other large particles you don't want in your water.

Not only is this important in creating clean water, but it also ensures these forms of sediment don't pass through subsequent filters, which can damage them over time.

Chlorine Filters

Following the sediment filter, there are two separate carbon filters; the first is a Granular Activated Carbon filter, the second is an Activated Carbon Block filter. The purpose of these filters is to absorb chlorine, as well as industrial solvents and other chemicals that cause bad taste/smell. These pre-filters prevent damage from subsequent filter levels, as chlorine contamination can be corrosive to these later-stage membranes. As with sediment filters, carbon/chlorine filters increase both filtration efficiency and filter lifespans.

The process is also referred to as adsorption, where the particles stick to the surface of the material rather than ‘soak’ into the material itself. This is why it’s important to have a larger surface area, such as the granules of the GAC or the fine powder that is made into a block in the ACB.

All carbon used in Express Water filters are also 100% coconut husk carbon. A third carbon filter is found after the membrane.

Reverse Osmosis Membrane

This stage handles the brunt of filtration in reverse osmosis systems. Reverse Osmosis Membranes are semi-permeable, meaning they allow some substances to pass through, while blocking others.

The membrane captures contaminants like lead, fluoride, chromium, as well as bacteria and other disease-causing microorganisms. This makes it the ideal filter for providing clean, healthy drinking water.

Post-Carbon Filter

This filter is the final stage of reverse osmosis systems. Post-filters help to further remove contaminants and also add beneficial minerals back into the water. These minerals help to improve the taste of the water, making it more palatable, as well as give your body the nutrients it needs

The post-carbon filter also uses a fine carbon powder made from 100% coconut husk carbon; often known as a ‘polishing’ filter as it removes any last tastes or odors before being consumed.

Additional filtration can involve:

  • Alkaline filtration: Adds essential minerals like magnesium, potassium and calcium, as well as increases the pH and oxygen level of the water.
  • UV filtration: Kills harmful bacteria and viruses without relying on chemicals. UV filtration uses ultraviolet light to destroy microorganism's DNA, killing them off and making them unable to reproduce.
  • Deionization filtration: This filter uses ion exchange to remove anything that isn't pure water.

What Is Deionized Water?

Deionized water is a type of purified water that's processed by removing ions and other impurities, resulting in water that contains no minerals or salts (which is why it's also called "demineralized water"). This means it doesn’t have the same taste as regular drinking water, but it can be used for various purposes such as cleanliness, medical treatments and more.

An "ion" is a charged particle. The process of deionization involves passing water through an ion exchange resin, which is a substance that attracts and binds ions in the water.

Deionized water can be used for many purposes. It's often used for medical treatments, such as dialysis or kidney transplants, because it does not contain any harmful minerals or chemicals that could be dangerous to patients’ health. Deionized water is also ideal for cleaning delicate electronics, such as computers and mobile phones.

What Does Reverse Osmosis Remove from Your Water?

Reverse osmosis systems remove:

  • Debris
  • Dirt
  • Dust
  • Fluoride
  • Lead
  • Pharmaceuticals
  • Chlorine
  • Arsenic
  • Viruses and Bacteria

The reverse osmosis system is an excellent way to ensure your water is clean, safe, and free from contaminants. Reverse osmosis systems are some of the most effective filtration systems available today. They can remove a wide range of toxins, including ones you may not even know are present in your drinking water. Investing in a reverse osmosis system can be one of the best decisions you make for your health and safety.

How Often to Replace Reverse Osmosis Filters

Reverse osmosis systems come with several filters designed to remove different contaminants, so it is important to replace these filters regularly so that your system can continue to effectively filter out pollutants from your drinking water.

Depending on the type of filter, you should replace it every 6 months or 1 year. Regularly replacing the filters in a reverse osmosis system will ensure that your water remains clean and contaminant-free.

It’s also important to keep an eye on the quality of the filtered water coming from the reverse osmosis system. If there are any changes in taste, odor or clarity, then it’s time to change the filters. This will help keep your reverse osmosis system running at optimal efficiency.

Overall, maintaining a reverse osmosis system requires regular attention and care. By changing the filters and membrane on a regular basis, you can ensure that your reverse osmosis system is working properly and providing your household with contaminant-free drinking water.

How to Replace Reverse Osmosis Filters

Replacing the filters and membrane in a reverse osmosis system is a relatively simple process. 

First, turn off the Cold Water Supply connected to the RO System, the Feed Water Adapter Valve, and the Tank Valve. Then open the RO Faucet handle to release pressure, close the handle when the flow of water stops.

Then, all you need to do is locate the filter housing, unscrew it from its position and remove the old filters and membranes.

It’s also important to make sure that you purchase new filters and/or membranes that are compatible with your reverse osmosis system. Once you have all of the necessary components, reassemble the filter housing and reinstall it onto the unit.

Your system will need to be flushed. Check the “system restart” section of this PDF

Now, you should be good to go!

At Express Water, customer support is available to help with any questions people may have.

It’s important to remember that regular maintenance is essential for keeping your reverse osmosis system running properly. By following these simple steps, you can maintain optimal performance of your reverse osmosis system.

For more in-depth instructions, click here.

Reverse Osmosis Water Health Effects

By reducing water contamination by 99%, reverse osmosis systems help provide clean and safe drinking water. This can have a number of health benefits, including reducing the risk for illnesses caused by certain contaminants in drinking water, such as lead or arsenic.

Other contamination that can have a detrimental effect on your health includes pesticides, herbicides, nitrates and pharmaceuticals. Reverse osmosis systems can help remove all of these contaminants from drinking water and improve the overall quality of the water you’re drinking.

The reverse osmosis process also helps remove bacteria, viruses and parasites from drinking water, making it safe for consumption.

Additionally, consuming reverse osmosis-filtered water may also help with skin conditions and reduce inflammation.

Overall, reverse osmosis systems are effective at removing many impurities from your drinking water. Regular maintenance is a key part of keeping these systems functioning properly so that you can enjoy the full health benefits of clean and safe drinking water. So take the time to regularly inspect your reverse osmosis system and make sure it’s running optimally!

Who Benefits Most from Reverse Osmosis Systems?

Reverse osmosis systems are designed to provide clean and safe drinking water for everyone.

That said, there are certain individuals who may benefit the most from having a reverse osmosis system installed in their home. These people include:

  • People with low immunity or weakened immune systems
  • Individuals on special diets
  • Those with allergies or sensitivities to chemicals and pollutants in tap water
  • Households that use well water
  • Families living in areas where tap water contains large amounts of toxic substances.

Frequently Asked Questions About Reverse Osmosis Systems

Q: What type of maintenance do reverse osmosis systems require?

A: Reverse osmosis systems need regular maintenance. This includes replacing the filters every 6-12 months and checking for signs of leaks or other damage. Additionally, it’s important to clean any parts that come into contact with water on a regular basis to ensure proper functioning of the system.

Q: How much does a reverse osmosis system cost?

A: The cost of a reverse osmosis system varies depending on the size and features you choose. Typically, basic models start around $125 to  $180, while more advanced reverse osmosis systems can cost up to several thousand dollars.

Q: How long does a reverse osmosis system last?

A: Typically, reverse osmosis systems can last for up to 10-20 years with proper maintenance. However, it’s important to regularly check and replace filters as needed in order to extend the life of your system.

Q: What are the benefits of using a reverse osmosis system?

A: The primary benefit of using a reverse osmosis system is that it provides clean and safe drinking water. Additionally, these systems are relatively easy to install, use less energy than other filtration methods, and require minimal maintenance. Lastly, they can also help reduce chlorine and other contaminants in water that may have a negative impact on taste or smell.

Q: What should I look for when selecting a reverse osmosis system?

A: When selecting a reverse osmosis system, you should consider the size of your household and the type of contaminants that are present in your water. It’s also important to factor in the cost of installation and any additional maintenance that may be necessary. You should also evaluate how easy it will be to replace filters as needed.


Investing in a reverse osmosis system is an investment in your family’s health and well-being. By investing in a reverse osmosis system, you can enjoy the peace of mind that comes with knowing that your family is consuming clean and safe drinking water on a daily basis.

Plus, these systems are a cost-effective way to ensure that you’re getting the highest quality water possible.

In summary, reverse osmosis systems provide numerous benefits including improved water taste, reduced contaminants, and easy installation and maintenance. With proper care and regular filter replacements, your reverse osmosis system can last for up to 10-20 years, depending on the model, so you can enjoy clean and safe drinking water for years to come.

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