How Does Reverse Osmosis Water Filter Work?

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How Do Reverse Osmosis Water Filters Work

Reverse osmosis is a type of filtration system that is used to treat unfiltered tap water. Water flows from one side of the RO membrane to the other, removing all contaminants and impurities, making the water safe for drinking.

People often ask questions about how reverse osmosis water filters work and how effective they are to use. Here, we will outline all the necessary information about reverse osmosis filters so that you can make an informed decision when it comes to making your purchase.

How Does Reverse Osmosis Water Filter Work?

Reverse osmosis filters work through various steps. Water passes through multiple filtrations to ensure it is pure, clean, and safe for drinking.

  • Prefilter: The prefilter is mostly made of carbon or sediment. Here, the water is purified of various sediments and chlorine. The water is then allowed to enter the RO membrane.
  • RO membrane: When water passes through this membrane, it leaves behind all the dissolved particles that a prefilter is unable to remove. This membrane removes even the tiniest particles and pathogens; the water that’s passed through this membrane is suitable for use.
  • Storage tank: After the filtration process is completed, the water is stored in a tank until use. The process continues until the storage tank is filled with clean water. Once the tank is filled, it does not overflow. Instead, the filtration process automatically stops.
  • Postfilter: Before the water reaches you, the water passes through one more filter as you pour it from the storage tank. This last step enhances the taste of the water and makes it perfect for drinking.

What chemicals are removed by reverse osmosis filters?

The reverse osmosis system is effective in removing dirt, chemicals, and microorganisms. The process is suitable for removing the following chemicals from the water:

  • Carbon
  • Sediments
  • Chlorine
  • Arsenic
  • Nitrates
  • Fluorides
  • Salt
  • Chromium

What contaminants are not removed by reverse osmosis filters?

Some contaminants that have smaller molecules than water slip through the filters and the RO membrane. Hence, they are not removed and still present in filtered water. These include:

  • Herbicides
  • Dissolved gases such as hydrogen sulfide
  • Pesticides
  • Some organic compounds

Does reverse osmosis filter remove healthy minerals?

Yes, during reverse osmosis filtration some essential minerals are also eliminated. Some healthy minerals that the RO filtered water will not contain are:

  • Iron
  • Calcium
  • Manganese
  • Sodium
  • Lead
  • Zinc
  • Selenium

How much water is wasted during reverse osmosis filtration?

Using a reverse osmosis filter will result in some water wastage. As the impurities are stripped out of the drinking water, they become more highly concentrated in the wastewater. This wastewater, containing salt, impurities, and other dissolved chemicals, cannot be used for drinking.

To obtain 1 gallon of clean, filtered water, approximately 4 gallons of water is wasted. Thus, water wastage should be kept in mind when installing an RO filter.

Although the contaminated water still contains many impurities, it can be used for different purposes such as watering your plants or garden and washing the garage and other outdoor areas.

To do this, there are a couple of options. Either an ASO valve can be installed, which stops the flow of contaminated water towards the drain. The other option is to get a permeate pump. This pump helps to reduce the wastewater by almost 80%. This is a very good option in situations where there are water shortages and installing the RO filter is the only option to get pure filtered water.

RO membrane pore

For how long does the RO filter last?

The RO system lasts easily for up to 15 years. However, the filters and the membrane need to be replaced depending on the usage and the quality of water in your area. An average timeframe to replace your filters is within a year, while the membrane lasts up to 2 years. If the water does not have too many impurities, the membrane can be used for a little longer.

Benefits of using the RO filters

There are a lot of benefits to installing an RO filter. Some of them include:

  • Improves and enhances the taste of water.
  • Bad odors are removed.
  • Sodium is completely eliminated.
  • Cheaper than bottled water.
  • Environmentally friendly compared to bottled water.
  • Cost-effective.
  • Easy to install and use.
  • Low maintenance.
  • Provides good quality water for drinking and cooking use.


You’ll find a lot of different kinds of water filters on the market. RO filters are the most reliable and trusted water filters used worldwide. Once the system is installed and it starts functioning, you don’t have to worry about accessing clean water anymore.

Since all the contaminants and impurities are removed, your overall health will improve. The system is simple and effective, which means there’s hardly any chance of the equipment breaking down as long as the necessary parts are replaced in a timely manner. The filters and the membranes are made of good quality materials, which completely ensure that no impurity or contaminant enters the drinking water.

Reverse osmosis filters are ideal for places where people struggle for clean drinking water and suffer from health problems due to unclean water. It is a cheap and simple method that can be used at home or commercially.

Also Read: How to Remineralize Reverse Osmosis Water

Jeremy Lee is a researcher and part-time blogger who has a passion to discover cutting-edge technologies related to water filtration. He knows the importance of purified water in our lives and started this blog aiming to provide the best product reviews, buying guides, and other useful information related to water. When not working, he loves to spend time with his beloved wife and two kids.