Is RO Water Purifier Necessary In India?

The answer depends on whom you put the question to. Suppose you ask the RO water purifier salesperson this question. You know what answer you will get. According to them, the RO water purifier is the solution to all water purification problems.

But, is it so?

No. It is not because various factors decide which water purifier you should purchase. So, an RO water purifier is not always necessary. Let us understand why and when you need an RO water purifier.

But, before that, we shall discuss why you need a water purifier in India.

Here are some statistics you should know..

India is the largest consumer of Groundwater in the world

So, the statistics show that TDS levels in India are high, necessitating the use of water purifiers. So, it brings us to the discussion on TDS and how it influences your choice of water purifiers.

What is TDS?

Everyone knows that TDS stands for Total Dissolved Solids. These solids constitute inorganic salts like magnesium, calcium, sodium, potassium, chlorides, sulfates, bicarbonates, and nitrates. Besides, organic matter and minerals add to the contaminants, making the water hard. Organic matter includes sewage, industrial waste, and urban run-off. 

what is tds

But are all these salts harmful? No, because you need salts like calcium and magnesium to improve your health quotient. At the same time, arsenic, fluorides, and nitrates can be dangerous. So, it becomes imperative to remove these contaminants.

So, how much TDS is good for health.

Let us see what WHO says about TDS levels in the water.
  • The World Health Organization says that TDS levels of less than 600mg/l should be suitable for drinking.
  • As the TDS levels cross 1000mg/l, the water becomes increasingly unpalatable.
  • However, reliable statistics are not available associating TDS’ health effects and ingestion.
Here is what the Bureau of Indian Standards specifies
  • BIS states that TDS levels up to 500mg/l are acceptable. The upper ceiling is 2000mg/l (IS IO500:2012). Therefore, water with TDS levels of more than 2000mg/l is not potable, even after filtering.
  • BIS standards specify the use of RO water purification for water with TDS levels in the range of 500 to 2000mg/l.
The US EPA standards also echo similar sentiments

The US EPA categorizes water quality as Maximum-contaminant-level goal (MCLG) and Secondary Maximum-contaminant-level (SMCL). It has fixed an upper level of 500mg/l for recommending a water purifier. It is equivalent to the TDS levels prescribed by BIS.

Now, let us see the misinformation from various Indian websites and news reports
  • Kent, the primary RO water purifier manufacturer in India, states that TDS levels up to 250mg/l are suitable for consumption. However, it recommends using RO water purifiers if the TDS levels exceed 200mg/l.  
  • Similarly, Livpure, another top RO water purifier manufacturer, considers water with TDS levels of more than 250 as unfit for drinking.
  • Bisleri, a famous bottled water manufacturer, spreads similar misinformation about water with TDS levels of more than 250 as not recommended for drinking.

These websites have their compulsions because they market their products. But, we should understand these sales gimmicks and not rely on such misinformation. So, we shall stick to BIS and WHO standards and state that RO water purification is necessary if the TDS levels exceed 500mg/l.

What type of water purifier is ideal?

Statistics show that nearly 70% of groundwater in India is unfit for consumption without purification. But, what type of water purifier is ideal.

You have different types of water purification systems in India.

Ultra Violet Filtration – UV filtration is essential if there is bacterial contamination in the input water supply. The UV rays kill bacteria and viruses to purify the water.

Functioning of UV water purifier

Ultra-Filtration – UF consists of filters with fine pores to trap microscopic particles, including dead bacteria and viruses, after UV filtration. It can also handle the tiny pollutants that survive RO water purification.

Note that UV and UF do not tackle TDS in any way. So, these filters are ideal if the TDS levels in the input water source are less than 500mg/l.

Reverse Osmosis – RO water purification is necessary if the TDS levels in the water exceed 500mg/l. BIS states that RO purification can handle TDS levels up to 2000mg/l. But, please note that RO does not eliminate bacteria and viruses.

Related: RO vs UV vs UF

How does RO work?

While the discussion can get technical, let us make it as simple as possible. Those who have studied biology would have heard of the term ‘osmosis.’ For example, roots absorb water from the soil through a natural process known as osmosis.

Therefore, osmosis is the process of movement of the solvent from high water concentration to low water concentration through a semi-permeable membrane. Please note that the water concentration of the source is high. After passing through the membrane, the water dissolves the solids and reduces their concentration.

Reverse osmosis is the exact opposite process of osmosis, where the solvent moves from a low water concentration (high TDS) to a high water concentration area (low TDS) through a semi-permeable membrane. Since it is against the forces of nature, it is an artificial process where the solvent has to be pumped with pressure to overcome the natural osmosis process.

The reverse osmosis process involves the water leaving the solids behind and moving towards an area where its concentration is higher.

The natural movement of water is from a dilute area to a concentrated area. Reverse osmosis is the opposite. So, it requires the pumping of water with high pressure.

We now know the Reverse Osmosis concept. Let us see how an RO water purifier works.

How RO water purification works

We have already discussed that an RO water purifier is necessary if the TDS levels in the source water exceed 500mg/l. It means that the water might contain dissolved impurities in various concentrations. All these impurities are harmful to our health. Hence, RO purification is essential.

The RO water purifier has an RO membrane that traps all dissolved solids with molecular weight exceeding 20. So, lead (molecular weight – 207), arsenic (75), antimony (122), cadmium (112), etc., cannot pass through the membrane. Therefore, the resultant water becomes pure.

The Downsides of RO water purification

We have seen that the RO membrane does not allow harmful chemicals to pass through it. But, at the same time, it prevents essential minerals like calcium (40), magnesium (24), sodium (22), potassium (39), etc., from passing through. Therefore, the resultant pure water loses its crucial nutrients. So, how do you overcome this problem?

If you observe your RO water purifier, you will see that it comes equipped with either a TDS controller or a Mineralizer

TDS Controller vs Mineralizer

A TDS controller is a manual adjustment that allows consumers to control the TDS levels in the water.

Usually, the TDS controlling activity happens after the UF process. The TDS controller mixes RO-treated water and UF-purified water in a specific ratio to ensure the replenishment of essential minerals in the final water output.

However, users should note that the UF-purified water does not pass through the RO membrane. So, the water contains TDS. Hence, we do not recommend its use where the TDS levels in the input water source are more than 900mg/l.

Besides, we do not advise using the TDS controller in areas having water with high levels of arsenic or lead contamination. The mineralizer is a better option under such circumstances.

The mineralizer is a separate attachment that adds essential minerals like calcium, magnesium, etc., to the RO-purified water. The attachment comes as a specific cartridge that requires replacement at regular intervals. Therefore, a mineralizer seems a safer option because you get 100% purified RO water plus the essential minerals lost during the RO purification process. In contrast, the TDS controller gives around 90% RO-purified water.

So, can we consider the TDS controller to be less effective than a mineralizer? It is not so because the TDS controller is not recommended where the TDS levels are high. It works well if the TDS levels are up to 900mg/l.

Related: TDS Controller vs Mineralizer

Do RO water purifiers waste the water?

The most significant drawback of RO water purifiers is that they waste water. RO water purifiers have two water outlets. One carries purified water to the TDS controller or the mineralizer, whereas the other caters to discarding the rejected water. The rejected water depends on the TDS levels in the input source water.

RO water wastage

Usually, an RO water purifier wastes two to three glasses of water while dispensing with one glass of RO-purified water. So, for every 100 liters of input water, nearly 60 to 70 liters of water go waste. That is criminal wastage, considering that many places in India face acute water shortages.

Can you use the rejected water from RO water purifiers?

Yes. You can use the RO purifier rejected water for various uses like watering plants, cleaning floors, washing utensils, etc. But, you must have a process for collecting and recycling the wastewater.

Related: How to Make use of RO Reject water

Is a standalone RO water purifier a viable option?

No. The standalone RO water purifier is not viable because of its inherent drawbacks. For that, you should understand the different filtration stages in water purification.

Sediment Filter

Usually, all water purifiers feature an externally-placed sediment filter to remove the large visible impurities from water. This arrangement protects the expensive components of the RO water purifier like the RO membrane and makes its job more manageable.

Sediment Filter
Pre and Post-Activated Carbon Filters

Besides TDS, the source water can contain volatile organic compounds and a foul odor. Initially, the input water passes through the Pre Activated Carbon filters to remove VOCs and foul odor. Usually, there is another Post Activated Carbon Filter to eliminate residual organic contaminants after RO purification.

RO Membrane

The RO membrane eliminates TDS from the input water source and purifies the water.

RO Membrane

The UF method is usually separate from the RO membrane because it filters minute contaminants like bacteria, viruses, cysts, etc., from the water source before combining with the RO-purified water through the TDS controller arrangement.

TDS Controller

This feature mixes RO-purified and UF-purified water in a specific adjustable ratio to ensure the retention of essential minerals like calcium, magnesium, etc.

TDS Controller

The mineralizer has a unique cartridge that replenishes the essential minerals like magnesium, manganese, calcium, etc., to enhance the RO-purified water’s taste and nutritional value.

Ultra-Violet Filtration

UV filtration is crucial because this process eliminates harmful bacteria and viruses from water to enhance the health quotient.

So, an RO water purifier with these additional filtration arrangements is better than a standalone RO water purifier.

Now, we shall discuss when one should go for an RO water purifier.

When to go for an RO water purifier?

As discussed above, RO water purification is essential when the TDS levels in the input water source exceed 500mg/l. So, people relying on well water, groundwater, or river water supply should generally prefer an RO water purifier after testing the TDS levels in the water.

TDS Meter

Testing TDS levels should not be a problem because TDS meters are available in the market for less than Rs 200. These TDS meters are easy to use and instantaneously give TDS values in water. So, if the TDS levels exceed 500mg/l, we recommend using an RO water purifier.

So, does it imply that TDS levels below 500mg/l do not need RO purification?

Generally, water with TDS levels less than 500mg/l (500ppm) does not require using RO water purifiers. However, much depends on the water source.

  • If you live in areas near industries, there are chances of industrial pollution and water contamination. The input water source can have TDS levels between 300 to 500mg/l. However, there could be arsenic or lead contamination in water. Therefore, RO water purification becomes essential.
  • Similarly, people depending on untreated river water should also prefer RO water purification because there can be sewage contamination and animal waste in river water. Under such circumstances, we advise using RO water purifiers even if the TDS levels are below 500mg/l.

When is RO water purification not necessary?

Generally, you do not need RO water purification when TDS levels are below 500mg/l. Besides, municipalities in various cities supply RO-purified water to their inhabitants through water pipes. So, people depending on RO-treated municipal water supply need not invest in RO water purifiers.

However, they can use UV and UF water purifiers to remove bacteria, viruses, microorganisms, and other microscopic contaminants. But, we recommend checking the TDS levels in the water before purchasing a water purifier.

UV water purifier from pureit

How can you reduce TDS levels in water?

We have seen that RO purification is the best way to reduce TDS levels in the water. However, rainwater harvesting is also an excellent method to reduce TDS levels in groundwater. So, we suggest every dwelling should have rainwater harvesting arrangements to improve and replenish groundwater quality.

Does water softening reduce TDS levels?

Water softening does not drastically reduce TDS levels. Water softeners replace essential minerals like calcium and magnesium in the source water with sodium. So, you can find a minor reduction in TDS levels, but you might also have to contend with reduced calcium and magnesium content in the water.

Is RO water purifier good for health?

Yes. RO water purifier removes harmful chemicals like arsenic, lead, cadmium, antimony, etc., from the source water and enhances the water quality. So, it is suitable for health. However, the purification process also removes essential minerals. Therefore, we suggest using RO water purifiers with mineralizers to replenish the minerals lost during RO water purification. Besides, it is advisable to use RO water purifiers that offer UV/UF purification.

Is RO water purifier safe to use?

RO water purifiers are safe to use. However, RO purified water has a low pH value (around 7). Therefore, though the water is pure, it lacks taste. Besides, continuous water consumption with low pH values can lead to gastrointestinal and renal problems. Consequently, we suggest using mineralizers that enhance the alkalinity quotient and make the water slightly alkaline (pH value > 7). 

Some websites say that consuming RO water can cause bloating, stomach aches, gastric ulcers, etc. But, our dietary habits also play a critical role in maintaining our health. Therefore, blaming RO water consumption alone is not proper. Besides, consuming contaminated water can lead to other diseases.

Many people feel that RO water cause hair loss. But, how many people wash their hair with RO water? Usually, chlorinated water is the prime cause of hair loss. Secondly, the indiscriminate use of chemical shampoos and hair products is also responsible for hair loss.

Are RO water purifiers banned in India?

Presently, there is no ban on using RO water purifiers in India. The National Green Tribunal (NGT) had directed the Central Pollution Control Board to issue directions to all RO water purifier manufacturers to ban RO water purifiers where the TDS levels are below 500mg/l. However, the Supreme Court has stayed the order and sent notices to the Central Government to present their views on the matter before the Honorable Supreme Court.

NGT contends that RO water purifiers waste a lot of water (a precious natural resource) during the purification process. Besides, RO water purification eliminates essential minerals from the water. So, the ban was a directive to RO water purifier manufacturers not to aggressively market their RO water purification products, especially if the circumstances do not warrant their usage.

What are the maintenance costs of RO water purifiers?

One of the prime drawbacks of RO water purifiers is that they frequently require proper servicing and filter replacements. The RO membrane and both the activated carbon filters have specific lifespans. So do the mineralizer, UV lamps, UF membranes, and sediment filters.

Generally, you change RO membranes and activated carbon filters once in two years. Usually, the cost of these filters is around Rs 3000 to Rs 4000. The UV lamps also require replacement. But, these lamps are inexpensive. So, replacing these lamps should not be an issue.

So, this brings us to the main question. Is RO water purifier necessary in India?

The answer depends on the TDS levels and the degree of water contamination.

  • RO water purifier is necessary if the TDS levels in the input water source exceed 500mg/l. Though BIS stipulates 2000mg/l as the ceiling, we can safely consider TDS levels more than 1200mg/l unacceptable.
  • If you reside in places with high levels of industrial contamination and human/animal wastage in water, we recommend using an RO water purifier, regardless of the TDS levels.
  • An RO water purifier is unnecessary when households receive municipal water supply previously treated with RO purification. Instead, a UV and UF water purifier should suffice.
  • RO water purification should never be used standalone. Instead, we suggest combining UV/UF water purification as a supplementary to RO water purification.
  • Using RO water purifiers with mineralizers is better than TDS controllers.
  • People should be aware of sales gimmicks used by RO water purifier manufacturers. You can test the TDS levels yourself using the TDS meter. You need not depend on the salesperson’s advice.
  • It is better to go for natural water purification methods like rainwater harvesting to reduce TDS levels in groundwater. Housing colonies and apartment complexes can install rainwater harvesting equipment for the benefit of the inhabitants.
  • We advise RO water purifiers as a need-based solution rather than a status symbol.


The RO water purifier is not an absolute necessity for every home. Various factors are crucial in deciding whether you invest in an RO water purifier. We have discussed the matter in detail. We sum up as follows.

  1. RO water purifier is essential if the TDS levels in the water exceed 500mg/l.
  2. As far as possible, please invest in an RO water purifier that offers additional water purification like UV and UF.
  3. A mineralizer is a better option than a TDS controller.


Chaithanya Vanjari
Chaithanya Vanjari
I'm Chaithanya Vanjari, the Creator and Editor-in-Chief at KitchenArena. With a decade of experience in evaluating large appliances like air conditioners, washing machines, refrigerators, and various small home devices, I possess the technical expertise needed to thoroughly review and understand the operational complexities of these appliances.


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