RO Water Purifier? (Reverse Osmosis) – Pros and Cons Explained!

RO Water Purifiers are considered as the most efficient and reliable water purifiers which can also purify the water with High TDS levels.

Reverse Osmosis, Ultraviolet, and Ultra Filtration are the three most common water purification systems that are available for consumers.

In this post, I am going to talk about the Reverse Osmosis Water Purifier and the pros and cons.

What is Reverse Osmosis?

In order to understand what reverse osmosis is, let us go back and understand the concept of osmosis.

Liquids, especially water have a natural tendency to move from an area of lower concentration to a higher one when separated by a semipermeable membrane. The absorption of water by the roots of the plants is the best example of osmosis.


Reverse osmosis is the exact opposite of osmosis. In this process, the liquid moves from an area of higher concentration to that of a lower one, again through a semipermeable membrane. This is against their natural tendency.

Hence, you need to apply force. One of the best examples that come to mind is the desalination of water.


The role of the semipermeable membrane is very important in Reverse Osmosis. This membrane performs a selective role in the sense that it allows some molecules to pass through while restricting the others depending on their size.

Most of the houses have screen doors that allow air to pass through but deters the insects like flies and mosquitoes.

The semipermeable membrane is similar in many aspects. The best quality of the semipermeable membrane is that it allows for the flow of liquid in a single direction. This is because of the force you exert during reverse osmosis.

Reverse Osmosis is extremely useful for separating pure water from other solvents.

It also helps in the elimination of dissolved solids in water whereby you get pure water to drink.

RO forms the core aspect of most of the water purifiers in the market. Let us look at how RO water purifiers work.

The RO Water purifier concept

In a normal filtration process, you see the collection of impurities on the filter media that you have to discard before reusing it.

This process requires frequent maintenance. The RO water purifiers work on a different concept known as cross filtration.

This concept provides for using two outlets. One is for the pure water to flow through whereas the other outlet caters to the elimination of contaminated water, also known as reject water in industry circles.

PH Value RO water purifier

This reject water contains an overwhelming 93% to 95% of impurities.

Some people advocate recycling this water back into the filtering machine. However, that can cause a strain on the machine especially if the concentration of contaminants is high.

You can either drain this water out or use it for alternative purposes such as washing toilets, floors, etc.

An efficient RO system can eliminate 99% of TDS (Total Dissolved Salts), molecules, ions, and also impurities like viruses, bacteria, and pyrogens.

In the normal course, contaminants having a molecular weight in excess of 200 do not pass through the RO filters.

To put things in proper perspective, 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 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 take care of the heavy metal impurities but allow gases like Carbon dioxide (CO2) to pass through.

Hence, you find RO-treated water as slightly acidic with a pH value below 7. It is a very effective method to treat groundwater having a high concentration of TDS.

Various components of an RO water purifier

You have decided to purchase an RO water purifier system. Therefore, it is important you know the various components of an efficient RO system.

Inlet valve

This valve fits into the water source, your tap. You have a tube that attaches to the sediment filter.

Sediment filter

This is the first stage of filtration. Your water source can contain visible contaminants like sand, dirt, etc that could clog the RO system. Passing the water through this sediment filter ensures the removal of such visible impurities.

Pre-activated Carbon filters

Chlorine is an important ingredient in almost all municipal water sources. This chlorine can damage the RO membranes. Hence, you need to eliminate chlorine from water. The pre-activated carbon filters help you in doing so.

RO Membrane

This part of the machine consists of the RO semipermeable membrane. The majority of the impurities are eliminated at this stage.

However, as stated earlier some contaminants like certain bacteria and microorganisms do sneak through the RO membranes. You need supplemental filtration methods like Ultra Violet (UV) and Ultrafiltration (UF) to ensure maximum purification.

UV filters help in removing bacteria and microorganisms whereas UF filters remove the remaining traces of contaminants.

The next stage of water purification involves passing of this filtered water through activated carbon filters to remove any unpleasant smell that remains after the filtration process.

The RO filtration can remove many vital minerals from the water. Hence, the final stages of water purification involve the use of mineralizers to enhance the mineral content of water.

RO water purifcation

The filtered water then passes on to a storage tank for human consumption.

There is an automatic Shut-Off valve that ensures to switch of the flow of water into the tank. This triggers a process whereby the system shuts off. As you consume the water from the tank, the pressure inside the tank reduces thereby activating the machine again.

The impure water or the reject water is drained off through a separate outlet.

The machine has a check valve that prevents the backward flow of water from the storage tank. Similarly, you have flow restrictors to maintain the pressure on the inlet side of the membrane. This is to prevent wastage of water.

What is Reverse Osmosis Water Purifier?

A Reverse Osmosis Based Water Purifier Does not use any Compounds or Light to Purify the Water. The RO Purifier uses a Very Fine membrane up to a few microns to purify the water by hindering the impurities to pass through the membrane.

The Membrane in a Reverse Osmosis Purifier is what makes the RO Purifier Stand Out in the Crowd and makes it the Best Water Purifier for Home Purpose. The Membrane present in the RO Purifier can also remove the Dissolved Salts in the Water, which is not possible in other types of water purifiers.

The RO Membrane is capable of removing impurities like Dust and Mud from the water.

All the Bacteria, Viruses, Cysts, toxic antibodies, fluorides and Dissolved Salts like Arsenic, lead, iron and cadmium are removed from the Water.

If you live in an Area where the TDS levels in the water are high, you must consider buying an RO Water Purifier.

The Dissolved Salts like Arsenic, Lead are more Dangerous than the Bacteria and Dust. These are the Heavy Metals which Doesn’t show an immediate effect, rather they act like a slow poison and affect your health in the long term and can cause severe health issues like cancer and nerve damage.

Children are most affected than the adults by the TDS present in the water.

The Heavy Metals I have mentioned above have 5 Times more Gravity than that of the Water.

  • Arsenic – 5.7 grams per cubic cm
  • Mercury – 13.546 grams per cubic cm
  • Cadmium – 8.65 grams per cubic cm
  • Lead – 11.34 grams per cubic cm

As I mentioned earlier, these Dissolved Poisonous Salts can be removed only by the RO Water Purifiers.

Reverse Osmosis Water Gives the Safest Drinking Water even with the Water that has High TDS levels.

Please note that a Normal RO water Purifier can not clean the Water that has TDS levels in Thousands

Note: Do not buy Cheap or Unbranded RO water purifiers. These types of water purifiers will remove all the dissolved salts from the water including the useful ones. So, Always go for an RO water purifier that comes with a TDS Controller or Mineralizer that retains the natural Minerals in the water.

Types of Reverse Osmosis Water Purifiers

In India, they are two kinds of RO purifiers available for the Home Purposes.

  • Undersink RO Purifier
  • Wall Mounted Ro Purifier

Both the Undersink and Wall Mounted RO Purifiers have a Storage Tank that stores the Purified Water. Even though there is a Power Outage, the water stored in the tank will be available for use.

Under sink Ro Water purifier

Wall Mounted Reverse Osmosis Purifier in India

The Wall Mount RO purifier is the most widely used purifier in India which commonly have a storage capacity of 5-10 liters.

The Only Problem with the RO water purifiers is, there is some water wastage. So, you have to use the Dirty water in a proper way; to clean the house and mopping purposes.

Undersink RO Water Purifiers

The Undersink RO Purifiers are gaining a lot of popularity since they can be easily fitted under the Kitchen sink.

The Pure Water Outlet Tap is fixed next to your Kitchen Tap and will be very easy to operate.

These type of Ro Purifiers are fitted with the Air Pressurized RO Water storage containers that have a storage capacity of 5 liters.

These Purifiers are often referred as Under the Counter, Kitchen Sink Water Purifiers.

The Undersink RO Purifiers are acknowledged as the Best Water Purifiers for Home Purpose since the are Kept under your Kitchen Sink and doesn’t occupy much space.

The Pure Water comes from the Tap that will be fitted next to your kitchen sink tap.

As I mentioned earlier, the waste water can be used for Outdoor purposes. You can also use the water for Gardening.

The Undersink Water Purifier is more suited than the Wall Mount Ro Purifier. Since the under sink RO Purifier has a pressurized tank, the pure water comes out with more force.

Advantages of Reverse Osmosis Water Purifier

  • The RO Water Purifier Not only kills the Viruses and Bacteria but also removes their Dead Bodies from the water which is not possible in UV water purifiers.
  • Removes the Heavy Metals like Arsenic, Lead and the Dissolved Salts from the Water.
  • RO with TDS Controller/Mineralizer retains natural minerals in the water.
  • Compact and Easy to Maintain, operate.
  • You get safe and tasty drinking water.

Disadvantages of RO Water Purifier

  • Requires High Pressure and the Water is wasted in Reject Stream.
  • If you input 2 liters of Water into RO Purifier, you will get only one liter of pure water. (you can use this water for Mopping, Gardening, and Outdoor purposes)
  • Requires Electricity to operate.
  • The Quantity of the Reject Water is the same as the Quantity of Pure Water you get. About 50% of the Water processed through the Ro Water Purifier is Rejected.

The Advantages of the RO Water Purifier Outdoes the Cons of it. The above disadvantages are very minor when compared to the Advantages of RO Water purifier.

Now, you Know everything about the Reverse Osmosis Water Purifier. All you have to do is pick the Right RO Purifier that suits your needs. If you have any Queries Regarding Water Purifiers, Post them in the comments section below, and I’ll be happy to answer them.

20 thoughts on “RO Water Purifier? (Reverse Osmosis) – Pros and Cons Explained!”

  1. Kindly suggest 2 – 3 best ro purifiers with price. The place (Siliguri, west bengal) where I am living has tds around 300. Is it essential to go for ro.

    • Hi, if the TDS levels are lower than 300ppm, RO water purifier is not required, you can simply install a UV UF water purifier like Kent Maxx. If you are not sure about the TDS levels or you get water from multiple sources, it is better to install an RO water purifier that comes with a TDS Controller or Mineralizer, Kent Grand, Livpure Glo, Havells Max. If budget is not your concern, you can go with LG RO water purifier.

  2. I am having a TDS of 289 so which one do yu recomment kent prime or bluestar majesto only these two comapnies have service near. the water is from borewell.

  3. Hello,
    How about boiled water. we get municipal water and tds level less than 200. it it good to boil it and drink. we r used to do the same so far. do the ro systems completely eliminate tds?

    • You don’t need an RO water purifier as the TDS levels in your water are good. RO water purifiers that don’t have a TDS Controller/Mineralizer removes all the TDS from the water and they are not recommended. In your case, you can go with a UV/UF water purifier which gives purified water that is as safe as boiled water. Also, there will be no water wastage and the maintenance cost will also be low for UV/UF water purifiers.

  4. Does not the 50% reject with higher concentration of unwanted components pollute the ground water when it is used fo gardening etc ?

    • RO is enough to remove all the bacterium, virus, cysts, Hard metals and salts. But, most of the brands make RO water purifiers with UV or UF combination. UV, UF is there for the backup purpose. This will also improve the life of RO membrane.

  5. Aquaguard Genus is one of the best RO water purifiers. Most of the RO water purifiers from Kent, Pureit and Aquaguard comes with a TDS Controller or Mineralizer. So, No Minerals will be lost during the purification process. So, No matter the water source (Borewell, Municipality Tanker, Tap Water or river water), these water purifiers are suitable. I have mentioned all the Top RO Models on this site. Just visit the Homepage and browse through the posts to find the suitable model.

  6. Hi Chaitanya, Are there any water purifiers which purifies water based on the water quality.Like If the water is from municipality and with low TDS normally it doesn’t need an RO purification and if the water is from borewell with high TDS, purifirer uses RO. I did check out in Aquaguard which has one model DR. Aquagaurd Genus . Basically an Intelligent water purifier. Reason behind this question is currently i’m getting a muncipality water..UV/UL purifier should do. Since there are no rains and there is a talk that water could be rationed in future, so if at all we have to use borewell ortanker water

  7. i am getting supply water and not sure of tds level i am confused while buying ro any health hazzard using RO if TDS level is low

    • You can use an RO water purifier even if the TDS levels in your water are low. But, make sure you buy an RO water purifier that comes with a TDS Controller or Mineralizer, so the vital minerals will not be washed away. Kent, Pureit, Aquaguard and Livepure Ro water purifiers come with TDS controller. Have a look at the posts in this site to find the right water purifier.

  8. Thanks for the informative article. Is there any disadvantage using RO purifier for river water. I am not sure of the Tds level of this municipility suppy water. I want install Uv RO.

    • Always buy an RO water purifier form reputed brands like Kent, Aquaguard, or Pureit. No matter the TDS levels, these branded water purifiers comes with a TDS controller that maintains the natural minerals in the water and removes the dangerous hard metals and salts.

    • No, Rain water also have the same TDS levels. But Mineral Deficiency in the water is bad. Some non-branded RO water purifiers remove all the salts in the water which is not good for health.

      So, Always buy an RO from a reputed brand that can retain the natural minerals in the water.


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