This article discusses the different stages of a reverse osmosis water filtration system. A basic standard reverse osmosis drinking water system will have 3 stages of filtering, while a 5 stage system will have a carbon filter to remove chlorine, a reverse osmosis membrane to remove sodium, and an optional stage for adding healthy minerals.

Stages Of Reverse Osmosis

The stages of reverse osmosis typically include:

1- Pre-filtration

The first stage of a reverse osmosis system is the sediment pre-filter. This filter helps to reduce the presence of large particles, such as dirt and sediment, in the water supply.

2- Carbon filtration

The second stage consists of a carbon block or granulated activated carbon filter that removes chlorine, organic chemicals, and other contaminants that affect taste and odor and other chemicals from the water.

3- Reverse osmosis membrane

In the third stage water is forced through a semi-permeable membrane that removes dissolved solids, including sodium and other minerals, from the water.

4- Storage

The purified water is stored in a tank for future use.

5- Post-filtration

Now water is filtered through a final activated carbon filter to remove any remaining tastes or odors before it is dispensed.

Reverse osmosis systems are effective at removing dissolved solids and chemicals from your water supply to provide clean drinking water for you and your family.

3 Stage vs 5 Stage Reverse Osmosis

A 3-stage reverse osmosis (RO) system typically includes a pre-filter to remove sediment and two carbon filters to remove chlorine and other chemicals, as well as a semi-permeable membrane to remove dissolved solids and contaminants.

A 5-stage RO system typically adds two additional stages of filtration to the 3-stage system. These additional stages are a second carbon filter to further reduce any remaining chlorine and chemicals, and a post-filter to remove any remaining tastes and odors.

The additional stages in a 5-stage RO system can provide increased levels of water purity, taste, and odor removal compared to a 3-stage system. However, a 5-stage system may also require more frequent filter changes and may be more expensive. The decision between a 3-stage and 5-stage RO system depends on the specific needs and preferences of the user.

Understanding Reverse Osmosis Water Filtration Stages

Reverse osmosis is a sophisticated water purification process that effectively removes unwanted molecules, salts, and other contaminants from the feed water supply. The process involves a series of stages, with each stage designed to remove specific types of pollutants from the water.

The first stage of reverse osmosis involves carbon filtration to remove pollutants such as chlorine, chloramines, and volatile organic compounds.

The second stage employs a carbon block filter, which helps to reduce unpleasant odors and cloudiness by removing colors and various chemicals that can affect the taste of water.

The final stage of reverse osmosis involves a membrane that can cope with common residential levels of contamination. This membrane allows only pure drinking water molecules to pass through, while rejecting larger molecules such as salts and other contaminants.

To achieve the desired filtration efficiency, reverse osmosis systems require a sediment filter to clear any minute sediment particles that may have made it past the carbon water filter. This is usually followed by a polypropylene sediment filter, which has a 1 micron rating. The next stage is the carbon pre-filter, which clears organics like pesticides and fertilizers while also removing chlorine to bring out a better taste and odor.

The carbon pre-filter can also contain a carbon water filter, which is designed to attract contaminants and sediments. The reverse osmosis stage removes particles with a negative charge, such as salts and other contaminants. Finally, a post filter is used to improve the quality of the filtered water by removing any odor or taste issues that may have been present before the RO stage. The post filter also helps rid water of any bacteria or viruses that were not removed by the reverse osmosis process.

Reverse osmosis filtration is achieved through the use of a semi-permeable membrane that filters out contaminants from drinking water. In a two-stage reverse osmosis system, remineralizer and alkaline filters may be placed after the second stage as optional third and fourth stages.

A one-stage RO system works similarly but with fewer filter stages, meaning that some minerals are not removed but passed on in the single stream of permeate water. The stages progress from the feed water being pushed through a series of filters and membranes, with total dissolved solids (TDS) levels being reduced after each stage until they reach the desired level. This ensures that the purified water will have a normal pH level and be award-worthy clean.

An additional alkalizing stage can be added to the reverse osmosis process to add a final polishing touch, which increases CO2 levels and balances out any acidity present in the tap water before it leaves the municipal plant.

The use of polyphosphate filters is a key step in the reverse osmosis system design, as it eliminates calcium carbonate scale. The reverse osmosis process can effectively remove 99% of dissolved solids that may be present in the water, making it an ideal solution for purifying drinking water.

The process starts with the municipal water and passes through the stages of reverse osmosis filtration. Once these stages are complete, the water goes through a carbon filter to help polish the drinking water, removing any non-harmful bacteria or odors that may still be present.

While combining multiple stages of reverse osmosis filtration can be confusing, it can be an efficient way to achieve more pure water in your home system.


What are the key components of a 3-stage reverse osmosis system?

A 3-stage reverse osmosis system typically includes a sediment pre-filter, a carbon pre-filter, and a reverse osmosis membrane. These components work in conjunction to provide basic water filtration.

How does a 5-stage reverse osmosis system differ from a 3-stage system?

A 5-stage reverse osmosis system features two additional filtration stages compared to a 3-stage system. These extra stages generally consist of a second carbon pre-filter and a carbon post-filter, which help further purify the water and remove contaminants.

Is a 5-stage reverse osmosis system more effective than a 3-stage system?

While both 3-stage and 5-stage reverse osmosis systems effectively filter water, a 5-stage system may offer better filtration due to the added carbon filtration stages. These extra stages can help remove more contaminants and enhance overall water quality.

What factors should I consider when choosing between a 3-stage and a 5-stage reverse osmosis system?

When deciding between a 3-stage and a 5-stage reverse osmosis system, consider factors such as your water quality, budget, and specific filtration needs. If your water has a high level of contaminants or you require a higher level of filtration, a 5-stage system might be more appropriate. However, if your water quality is already fairly good and you have a limited budget, a 3-stage system could be sufficient.

Can I upgrade my 3-stage reverse osmosis system to a 5-stage system?

In many instances, it’s possible to upgrade a 3-stage reverse osmosis system to a 5-stage system by adding the required components. This may involve installing an additional carbon pre-filter and a carbon post-filter to improve overall filtration performance. Nonetheless, it’s crucial to consult with a professional or the system’s manufacturer to ensure compatibility and proper installation.