What Is Reverse Osmosis? – Pros and Cons of RO Water Purifier!

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Water pollution in India is a significant concern. Polluted water is hazardous to health. You simply can’t just ignore the need of a water purifier. Among various types of water purifiers, Reverse Osmosis (RO) water purifiers are the most popular in the market.

Here, I will try to explain the basics in simple terms which will give you a better overall understanding of Reverse Osmosis mechanism and its applications.

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To understand the meaning of reverse osmosis, you must first understand the process of osmosis. It is a phenomenon that occurs naturally and is a process where a weaker saline solution migrates to a robust saline solution.


For instance, our kidneys absorb water from our blood or absorption of water by the roots of the plants are the examples of osmosis.

Reverse Osmosis (RO)

Reverse osmosis is the process of osmosis in reverse. Osmosis takes place naturally, which does not require energy. But to reverse the process of osmosis, the power is needed to make the solution more saline.

reverse osmosis

A reverse osmosis membrane is a semi-permeable membrane, which allows the movement and flow of molecules of water but doesn’t dissolve salts, bacteria, and organics.

Therefore, you require to push water through the reverse osmosis membrane by applying pressure, which is higher than the osmotic pressure.

How does Reverse Osmosis Work?

Reverse Osmosis is the process by which water is forced to pass through a semi-permeable membrane. This membrane has many pores of tiny size. It prevents certain elements contained in the water from moving, such as viruses, bacteria, sediments, chemicals, salts, minerals, and heavy metals.

reverse osmosis membrane

As the water cannot move from low concentration to high concentration, a motor is used. After that, the water is divided into two parts; the dirty water is sent down to the drainage, and the clean water is sent to the next step for its treatment.

This process leaves almost around 95% to 99% of dissolved salts behind in the stream, which it rejects. The concentrated feed water is required to overcome the osmotic pressure.

For better understanding, water (H2O) has a molecular weight of 18. At the same time, the RO filters do not allow ions of higher valency to pass through.

Now, sodium, which is a salt present in the water, is a monovalent ion. Therefore, sodium ions pass through the RO filters necessitating the use of supplemental filters to eliminate such ions.

RO filters can purify the heavy metal impurities but allow gases like Carbon dioxide (CO2) to pass through. Therefore, you find RO treated water a little acidic with a pH value below 7.

Reverse Osmosis is a very effective method to manage groundwater, having a high concentration of TDS.

Components of RO Water Purifier

Working of Kent RO
Working of Kent RO
  • Inlet valve: The inlet valve is attached into the source of the water, the tap.
  • Sediment filter: This is the first stage of purification. This filter removes all the large impurities and dust particles from the water. It is used only in places where the water contains a lot of pollutants.
  • Pre-activated carbon filters: It efficiently removes the organic chemicals and pesticides from water which are responsible for bad order and improves the taste of the water.
  • RO membrane: It is a semi-permeable membrane with many tiny pores. Most of the impurities are eliminated in this stage.

Types of Reverse Osmosis Water Purifiers

In India, there are mainly two types of RO water purifier people use in their home.

  • Wall Mounted RO Purifier
  • Under Sink RO Purifier
Wall mounted RO Water Purifier
Wall mounted RO Water Purifier
Under sink Ro Water Purifier
Under sink Ro Water Purifier

Wall Mounted RO Purifier

This type of water purifier is very popular and mostly used in Indian families. The storage capacity of this type of purifier is between 5-10 liters. The main problem of this water purifier is it occupies some space in wall.

Under Sink RO Purifier

Nowadays, Under Sink RO Water Purifier is also gaining popularity. This type of water purifier is very convenient as it can be easily fitted under your kitchen sink and doesn’t require much space.

Also you get pure clean water just next to your kitchen sink tap.

It comes with an air pressurized water storage tank which has a capacity of 5 liters. As the Under Sink RO purifier has a pressurized tank, the pure water comes out with more force.

Advantages of RO Water Purifier
  • The RO Water Purifier kills the Viruses and Bacteria.
  • Reverse Osmosis water purifier is the best solution for treating hard water.
  • It removes heavy metals like Arsenic, Lead, and the Dissolved salts from the water.
  • RO with TDS Controller/Mineralizer retains natural minerals in the water.
  • It is very compact and easy to maintain.
  • It is effortless to operate.
  • You get safe and tasty drinking water.
Disadvantages of RO Water Purifier
  • It requires high pressure, and in this process, water goes in the reject stream.
  • About 50% of the water processed through the Ro Water Purifier goes wasteful. If you input 2 liters of water into the RO purifier, you will get only one liter of pure water.
  • It requires electricity to operate.
  • The water taste is affected, and it becomes tasteless.
  • RO water purifier is costlier than UV or UF water purifiers.
  • It takes more time to purify.


We have just seen the reverse osmosis mechanism, its components, and different types of RO purifier. You are also aware of the pros and cons of the RO water purifier.

Now all you should make is a wise choice. And we hope these information will help you select the best water purifier for your home.

Source: Wikipedia, Puretecwater


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1 thought on “What Is Reverse Osmosis? – Pros and Cons of RO Water Purifier!”

  1. Under Sink RO Water Purifier sounds more economical.

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