RO Water Purifier – Pros and Cons Explained!

RO, or Reverse Osmosis, is the most common water purification procedure followed by almost everyone in India. RO is essential because of the high levels of TDS and heavy metal contaminants in water. Though the RO process wastes water, most prefer it to alternatives like UV and UF water purification.

Reverse Osmosis is the most effective water purification process to remove dissolved contaminants from source water. This process can remove TDS and heavy metal impurities dissolved in water to provide clean and hygienic drinking water.

How does Reverse Osmosis work?

Reverse Osmosis, as the name suggests, is the reverse of the natural osmosis process. The best example of osmosis is the absorption of water by plant roots. Roots absorb water from the soil. The principle of osmosis is that water or any liquid moves naturally from an area of lower concentration to a higher concentration through a semipermeable membrane.

Reverse Osmosis
Source: puretecwater

Reverse Osmosis is the exact opposite of this procedure. Here, the water or liquid moves from an area of heavy concentration (water with TDS and heavy metal impurities) to a low-concentration area through a semipermeable membrane known as the RO membrane.

Since this process is against the forces of nature, it requires additional force to push the water through the membrane. Therefore, RO water purifiers use inbuilt pumps to force the water through the RO membrane. The membrane traps dissolved impurities with molecular weight over 20, allowing water molecules to pass through.

Parts inside of RO Water purifier
Parts inside an RO Water purifier

Thus, the final product is pure water without any dissolved impurities. The dissolved contaminants are rejected through a separate outlet as reject water.

This water has a high TDS concentration and is unfit for human consumption. However, you can use it for other purposes like washing utensils, cleaning floors, watering plants, etc.

What is the RO membrane made of?

RO memberane

RO membranes are usually cellulose acetate or poly-sulfone coated with aromatic polyamides. These membranes have a pore size of 0.0001 to 0.0002 microns. Hence, they can trap the minutest dissolved contaminants and purify water.

What does Reverse Osmosis remove?

The RO water purification procedure removes dissolved contaminants. No other water purification can do it.

Pureit eco water saver indicators
Pureit RO Water Purifier

The ultrafiltration process can remove suspended particles in source water, and ultraviolet treatment eliminates bacteria, viruses, and other harmful microorganisms.

The RO purification process removes TDS and heavy metal impurities like arsenic, lead, antimony, mercury, and other contaminants that can cause severe health problems.

Usually, we do not use RO water purification to remove suspended particles in water. The particles can clog the membrane and render it ineffective. Therefore, top-quality water purifiers use sediment filters, pre-carbon activated filters, and UF membranes before the RO membrane to protect the expensive components and extend the machine’s lifespan.

Reverse Osmosis Changes water taste

The RO water purification process removes TDS from water and purifies it. However, the process removes essential minerals like magnesium, calcium, and manganese from the source water to make it tasteless.

Therefore, water purifier manufacturers reintroduce these lost minerals in various ways like fitting TDS controllers, Mineral enhancer cartridges, etc. These processes replenish the lost minerals and improve the water’s taste.

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RO Water Purifier Advantages

  • Reverse Osmosis water purification can remove dissolved impurities and is the most recommended procedure for eliminating TDS from water.
  • RO water purification can remove almost all the dissolved solids from water and produce water with a pH level of 7.
  • RO purification is essential whenever the TDS levels in the water source are more than 300 ppm. The Indian standards stipulate that RO is essential for water with more than 500 ppm TDS levels.
  • This water purification is the best for making groundwater potable. Therefore, people residing in coastal areas need RO water purification.
  • RO water purification is essential for removing dissolved industrial waste from water sources. In addition, it can deal effectively with heavy dissolved metal impurities like lead, mercury, and arsenic.
  • Many municipalities and large gated communities have massive RO water treatment plants to offer RO-purified water to their residents. It eliminates the need for individuals to invest in expensive RO water purifiers.
RO filter
RO filter

RO Water Purifier Disadvantages

  • The most significant demerit of the RO water purification method is water wastage. The water wastage depends on the TDS levels present in the source water. Usually, the wastage is one glass of water for every glass of water purified.
  • RO membranes are more expensive than UF membranes and UV lamps. Hence, an RO water purifier is comparatively more expensive.
  • RO membranes use proper maintenance and replacement after around one year. However, since these membranes are expensive, the water purifier’s maintenance costs increase substantially.
  • RO water purification changes the water’s taste. Hence, processes like TDS controller and mineral enhancer cartridges are necessary to restore the water taste.
  • RO water purification is generally never used as a standalone procedure. Instead, it works with complementing technologies like sediment filtering, pre, and post-carbon-activated filters, and ultraviolet and ultrafiltration procedures.
RO water purifier parts
Inside an RO Water Purifier

Reverse Osmosis – Frequently Asked Questions

1. Is RO water harmful to health?

Yes. RO-purified water without replenishment of essential minerals is not healthy for consumption. Studies have shown continuous consumption of RO-purified water can cause weakness, tiredness, headaches, muscular cramps, and impaired heart rate.

2. So why should we use RO water purifiers?

RO purification is the only way to remove dissolved contaminants from water. Water with heavy TDS levels is unhealthy and harmful for consumption. Therefore, RO-purified water with mineral enhancers is the best solution.

3. How do TDS controllers work?

TDS controllers use a process involving introducing source water without RO treatment to the RO-purified water to balance the TDS levels and make it ideal for consumption. TDS controllers are handy when the original TDS in water does not constitute toxic chemicals like mercury and arsenic.

4. How do mineral enhancers work?

Mineral enhancers use mineral cartridges that introduce essential minerals like calcium, magnesium, etc., into RO-purified water to enhance its taste.

5. What is the lifespan of the RO membrane?

The lifespan of the RO membrane depends on the TDS levels in the source water. Usually, RO membranes can last for four to seven years. However, in areas with high TDS levels, the RO membranes could need replacement annually or once in two years.

6. Can RO membranes be reused?

Used RO membranes do not have any domestic use. But they are helpful for the nanofiltration of seawater in industrial plants.

7. What is the average price of an RO membrane?

It depends on the RO membrane quality and pore thickness. Generally, a decent RO membrane for domestic use costs between Rs 2,000 and Rs 2,500.

8. Can hot water damage RO membranes?

Yes. Water with temperatures over 40 degrees Fahrenheit can damage RO membranes. Hence, all RO water purifiers have other pre-filtering arrangements that remove suspended particles and control the water temperature before it flows into the RO membrane.

9. When should you replace an RO membrane?

You must replace the RO membrane when you observe a significant change in the water taste.

10. How much TDS is good for health?

The ideal TDS levels in drinking water should be between 50 and 150 ppm.


  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.

    • Check out the below models.
      Kent Grand Plus
      Livpure Glo
      HUL Pureit Ultima
      Kent ACE Mineral

  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 ?

  5. Is it necessary to take a combination of RO, UV and UF purifiers as some brands are offering? Are only RO will do?

    • 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.

  6. 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.

  7. 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

  8. 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.

  9. 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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