Are RO Water Purifiers Really Villains As It Is Made Out To Be?

Are RO Water Purifiers Really Villains As It Is Made Out To Be?

Potable water is a basic human right. But, even many of the upper-middle-class metro dwellers in India get hard, unpalatable, contaminated water that is not fit for human consumption. Fortunately, they can afford RO ( reverse osmosis) systems that help decontaminate the water and make it fit for human consumption.

But RO systems are made to look like villains these days. RO manufacturers are charged with scaring people about TDS to sell their products. The classic premise of corporations exploiting gullible consumers is quickly bought by all. But are RO manufacturers really guilty? Do we really need to worry about TDS?

Let us explore in detail by understanding the drinking water quality in India, the role of RO and the government stance on banning RO water purifiers.

What is TDS?

TDS refers to Total Dissolved Solids. It is measured in mg/litre which is equivalent to ppm ( parts per million)

The dissolved salts typically found in water are calcium, magnesium, sodium, potassium, bicarbonate, sulfate, chloride, nitrate, and silica.

Calcium, Magnesium, Potassium and Sodium in appropriate quantities are necessary for health. But, other dissolved salts like sulfate and nitrate are detrimental.

As per the Bureau of Indian Standards, the acceptable range of Calcium is 70 mg/L and Magnesium is 30 mg/L. Harmful salts like nitrate and sulfate should be less than 45 and 200 mg/l respectively. Acceptable hardness, measured as the quantity of dissolved calcium carbonate is 200 mg/l and that of fluoride is 1 mg/litre.

The BIS guideline consists of numerous other parameters which need to be met. However, we are discussing only dissolved solids as other substances like lead, arsenic, etc are insoluble and can be eliminated using a UF membrane.

Quality of Ground Water In India

We all know that the quality of groundwater in India isn’t exactly the best. Nitrate levels of more than 45 mg/l are found in many districts of Andhra Pradesh, Bihar, Delhi, Haryana, Himachal Pradesh, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Orissa, Punjab, Tamil Nadu, Rajasthan, West Bengal, and Uttar Pradesh.

As per the Ground Water Quality Analysis report by the Government, there are numerous sites in Delhi, Rajasthan, Karnataka, Tamil Nadu, MP, Gujarat, UP, Maharashtra, Chhattisgarh, Punjab etc, that have unacceptable levels of sulfate. Even the levels of calcium, magnesium, fluoride and other dissolved salts are higher in many parts of the country.

You can take a look at the document on Ground Water Quality Data which gives in-depth details. Considering that groundwater supplies 85% of the country’s drinking water, this report would give a fairly good idea about the quality of water you get at your home.

Role of RO And Other Filters

Water purifiers have various purification stages. The significance of RO is that it is the only method accessible at the domestic level to remove dissolved solids from water. So, if your water has a TDS level higher than 500 or higher than acceptable levels of calcium, magnesium, sodium, nitrates, bicarbonates, fluorides or sulfates, you can’t drink it unless you use an RO purification system.

Ultrafiltration ( UF) is a method similar to RO and it doesn’t waste any water. But, the pore size of the UF membrane is larger at about 0.01 to 0.1 microns, while that of RO is 0.0001 microns. UF can remove bacteria, germs, heavy metals like lead, arsenic and iron from the water. But, it cannot remove dissolved salts.

A carbon filter on the other hand is used to absorb Volatile Organic Compounds ( VOCs) which impart an odour to the water.

RO and UF physically capture harmful germs. But, they cannot kill them. UV purification is the method by which you can deactivate bacteria, viruses and other harmful pathogens.

Citing a 2009 study by the National Institute of Virology, certain news reports say UV filters are inadequate for killing harmful pathogens. But, when you look at the details, you understand that the 8 purification units tested priced between Rs. 300 to 6900 aren’t RO water purifiers. 

So do you need an RO Water Purifier?

ro water purifier necessary

As you would have already understood, you can’t decide whether you need an RO purifier or not simply based on the TDS level. The best way would be to test the water to understand its composition and make a decision based on it.

If your water supply is from Municipal Corporations or surface water sources like rivers, lakes and ponds, then you may not need an RO water purifier. In such cases, the dissolved salts in your drinking water supply are mainly composed of calcium and magnesium and other components are usually under acceptable levels. 

So, you could rather buy a UF+UV water purifier to eliminate any harmful heavy metal or pathogens and enjoy your water rich in essential minerals. 

On the other hand, if you get borewell water, it may be contaminated with nitrates, sulphates and unacceptable levels of carbonates, calcium or magnesium. You can ascertain that only by testing the water from a lab. In such cases, you have to get an RO purifier even if the TDS level is less than 500.

Many people might think, ” Should I go through the hassle of testing water? Why not just get an RO water purifier to be on the safe side?” Well, it is best to avoid going the easy route because RO is not without negatives. Water that passes through the RO membrane is completely devoid of essential minerals which are necessary for your health. 

Your RO water purifier mixes the water purified by RO membrane with the raw input water to incorporate the necessary minerals. Manufacturers call this TDS adjustment mechanism MTDS. As a result, the contaminants too get mixed. But its concentration will be way less and in an acceptable range. 

As RO water generally is demineralised water with low levels of calcium and magnesium, it may have an adverse effect on your health in the long run. Certain studies cite long term intake of water with TDS level less than 100 may throw off your body’s electrolyte balance. So, if your water supply doesn’t have any contaminants detrimental to your health, it is in your best interest not to use an RO.

So, while indiscriminate use of RO water purifiers isn’t good, you can’t deny that it provides an invaluable service by providing clean, potable water to people who have a poor quality water supply. 

It is true that many manufacturers fool gullible consumers by marketing about 10-12 stages of water purification. But that doesn’t mean all manufacturers are guilty or that RO water purifiers are totally unnecessary.

NGT Ban on RO Water Purifiers

Last year, the National Green Tribunal banned RO water purifiers in places where water TDS is less than 500. As you can see, it isn’t the health department that banned RO purifiers, but the one concerned with the environment. 

This is because an RO water purifier wastes water worse than a toddler. For every litre of purified water, it wastes more than 3 litres. This is a major cause of concern for the environment and for the general population where the majority doesn’t have access to clean drinking water. NGT has raised demineralized water too as a point of concern. To overcome this, they have issued a direction to educate consumers about setting the water purifier’s output TDS level to 150.

Also, NGT did not issue a blanket ban on RO purifiers in areas where water TDS is less than 500. As per the guidelines of the expert committee, the order issued by NGT says, “ RO is not recommended if TDS is less than 500 ppm, provided the input water shall not have critical impurities, nitrates, fluorides more than the acceptable limits of 45 mg/l and 1mg/l.”

So we can infer that the body too acknowledges the level of water contamination. Hence, urges users to buy RO if necessary and use it responsibly.

How To Choose The Right Water Purifier For Your Needs?

ro water purifier necessary

As mentioned, a water purifier doesn’t necessarily need 7 or 8 stages of purification to provide clean drinking water.

The filters you need if TDS is higher than 500 or if water has a high level of contaminants are-

An external sediment filter to remove sand and other large particles. This helps enhance the life of other filters used inside the purifier.

RO- To capture dissolved salt, pathogens and heavy metals like lead, arsenic, iron etc.

UV- To deactivate bacteria, viruses and any other harmful pathogens.

Carbon Filter- To get rid of volatile organic compounds that imparts odour to the water.

UF- Many people wonder if UF is necessary for an RO filter as RO captures everything that UF does. But when you look into the details you understand why you need it. UF filter is used to eliminate heavy metals, bacteria and viruses from the raw water used to mix with the RO water to increase the TDS level. So, without UF, the raw water getting mixed will have a high concentration of harmful contaminants.

If water has TDS less than 500 and doesn’t have harmful dissolved salts in high concentration, you just need a UF filter to capture heavy metals, fluorides and harmful pathogens along with an external sediment filter, UV and Carbon filter.

How To Responsibly Use RO Water Purifiers?

  1. Test the water to understand its composition and accordingly, set the TDS level in the range of 50-150. 
  2. Use RO water only for drinking and cooking.
  3. Store the rejected water and use it to mop the floor, water plants or any purpose other than human consumption.
  4. Switch on the water purifier only when you need it. Most water purifiers start running when water in the tank falls below a particular level. As a result, it disperses reject water every now and then. So, either connect the outlet pipe to an external tank or switch it on only when you can store the rejected water.
  1. Change the filters periodically to ensure proper purification.
  2. Dispose the used membranes responsibly. As per the NGT guidelines, manufacturers are responsible for taking away the used filters and disposing them off correctly.


RO water purifiers are not evil. They are quite a necessity in many parts of the country where you don’t have access to clean drinking water. But it is the consumer’s responsibility to use RO purifiers responsibly and only if it is a necessity.


Nita Agarwal

Nita is a freelance writer passionate about home, decor and technology. She banks on her experience as a home blogger and tech reviewer to write in-depth content that is practical and useful.

Read more posts by Nita Agarwal


One Reply to “Are RO Water Purifiers Really Villains As It Is Made Out To Be?”

  1. Hi Smart home guide, this is one of the best expert articles I have ever seen in Indian media! Thanks a lot for educating us about all aspects of water filtration

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