High TDS, bad taste or borewell water? Don't buy a purifier until you know this

The first thing many people do after checking their home's water is reach for an RO purifier. The TDS is high, so it must need RO. The water tastes strange, so RO should fix it. The house uses borewell water, so an RO purifier seems like the obvious choice.

But these conclusions can be too quick.

Water quality is not determined by a single number, a particular taste or even the source of the water. A TDS meter can tell you something about dissolved substances, but it cannot tell you everything about the water. Similarly, borewell water isn't automatically the same from one locality to another.

That matters when you are about to spend thousands of rupees on a water purifier.

The better approach is to identify the problem in your water first, and then choose the purification technology that is designed to address it.

Why isn't every water problem an RO problem?

RO, or reverse osmosis, has become almost synonymous with water purification in Indian homes. There is a reason for that. RO technology can reduce many dissolved substances from water and can be useful when certain dissolved contaminants or high levels of dissolved solids are a concern.

But “RO removes more” does not automatically mean “RO is better for every home”.

An RO system has its own trade-offs. It needs electricity, its filters and membrane need periodic replacement, and the process can produce reject water. That means both maintenance and water use become part of the ownership equation.

For a household whose main concern is something that another technology can address, paying extra for an RO system may not necessarily be the most sensible choice.

This is why purifier shopping should not begin with the question, “Which RO purifier should I buy?” It should begin with, “What is actually happening with my water?”

What does a high TDS reading actually tell you?

TDS, or Total Dissolved Solids, is probably the first number people look at when assessing their water.

A home TDS meter can be useful for getting a quick indication of the concentration of dissolved substances in water. But it is easy to give this little device more importance than it deserves.

A TDS reading does not identify exactly which substances are contributing to the number. It also does not tell you whether bacteria or viruses are present.

That means a low TDS reading should not be treated as a certificate that the water is safe to drink. At the same time, a high TDS reading doesn't, by itself, tell you exactly what is wrong with the water.

Indian drinking-water standards cover considerably more than TDS. The BIS specification for drinking water, IS 10500, includes parameters covering physical, chemical and microbiological quality, including TDS, hardness, fluoride, nitrate, iron and microbiological requirements.

So if a salesperson asks for your TDS reading and immediately recommends a particular purifier, remember that one number cannot describe the entire quality of your drinking water.

Premium water purifiers

Does high TDS automatically mean you need RO?

Not necessarily. A high TDS reading is a reason to investigate further, particularly if your water comes from a source such as a borewell or another supply where dissolved substances may be a concern.

RO can be an appropriate solution in situations where reducing dissolved substances is the objective. But the TDS number alone doesn't explain what those dissolved substances are.

This is an important distinction because water with the same TDS reading can have a different composition.

If your TDS meter reads 500, for instance, the number doesn't tell you whether the dissolved material is primarily made up of one type of mineral or several different substances.

A proper water-quality test can provide a much more useful picture when there is uncertainty about the source or composition of the water. In other words, think of TDS as a clue, not a diagnosis.

What if the water tastes bad but the TDS is normal?

This is where another common assumption falls apart. Taste and odour can be affected by several factors, including chlorine, naturally occurring minerals and other substances in water. Plumbing and storage can also influence what eventually comes out of a tap.

So if your water tastes different from what you're used to, that doesn't automatically mean an RO membrane is the solution.

Activated carbon, for example, is commonly used in water-treatment systems to reduce chlorine and improve taste and odour. Depending on the water-quality problem, carbon filtration can therefore have a role alongside or instead of other purification technologies.

The important distinction is between “I don't like how this water tastes” and “I know what contaminant needs to be removed.”

The first is an observation. The second requires evidence.

Does borewell water always need an RO purifier?

Borewell water can have very different characteristics depending on the location and the geology through which the groundwater moves. It may contain higher levels of dissolved solids or hardness, but the exact composition cannot be determined simply by knowing that the water came from a borewell.

The same applies to neighbouring homes.

Two houses in the same broad area may not necessarily have identical water quality, particularly if they draw water from different sources or depths.

Groundwater can also contain naturally occurring substances such as fluoride, nitrate or iron in varying concentrations. That doesn't mean every borewell has a problem with these substances. It means the source alone isn't enough to decide which purification system you need.

This is why borewell users, in particular, can benefit from testing the water rather than making a purifier decision based purely on assumptions.

“Borewell water” tells you the source. It doesn't tell you everything that's in the glass.

Best RO purifiers

So what do RO, UV, UF and carbon filters actually do?

Once you know what you are trying to address, the technology becomes much easier to understand.

RO: Reverse osmosis uses a membrane to reduce many dissolved substances. It is relevant when the water has high dissolved solids or specific dissolved contaminants that RO is designed to reduce.

UV: Ultraviolet treatment is aimed at microorganisms. It works differently from RO and is not intended to remove dissolved salts in the same way.

UF: Ultrafiltration uses a membrane to physically filter certain particles and microorganisms. Unlike RO, it does not provide the same level of dissolved-solids removal.

Activated carbon: Carbon filtration is commonly used to reduce chlorine and improve taste and odour, while also helping with certain organic compounds.

This is why a purifier can combine several technologies.

An RO+UV+UF+carbon system isn't necessarily using four competing methods. Each component can have a different job. And this is also why the number of stages printed on a purifier should not be your primary buying criterion.

Best RO+UV+UF+carbon system water purifiers

Is a 12-stage purifier necessarily better than a 7-stage purifier?

Purifier marketing often makes stage count sound like a scorecard. Seven stages can sound good, but 12 or 15 stages can sound even better.

The problem is that stage count doesn't tell you whether those stages are useful for your water.

A purifier could have several stages performing different filtration or conditioning functions, while another model could use fewer stages to address the same core water-quality concerns.

The right question is therefore not:

“How many stages does it have?”

Ask instead:

“What does each stage do, and do I need it?”

The same thinking applies to mineralisers, alkaline cartridges, copper features and smart monitoring. These may have a purpose, but they shouldn't distract from the basic job of matching the purifier to your water.

How can you find out what is actually in your water?

First, find out where your water comes from. Is it municipal supply, borewell, tanker water or a combination?

Next, you can use a TDS meter to get an initial reading. If the reading is high or the water source is uncertain, don't stop there.

Look at other obvious characteristics such as unusual taste, odour, colour or turbidity. These observations can tell you that something deserves closer attention, but they cannot replace a proper water-quality test.

If you need to know about specific chemical or microbiological parameters, laboratory testing is the more reliable route.

This is particularly useful for households dependent on borewell water or supplies that change during the year. It is simply to avoid spending money based on one number or one assumption.

What should you check before buying a water purifier?

Once you have a reasonable understanding of your water, then start comparing products.

• Look beyond the headline features and check:
• Which purification technologies does it use?
• What contaminants is it designed to address?
• What is the filter replacement cost?
• How often do the filters and RO membrane need replacement?
• How much water does the RO system recover?
• Is service available in your area?
• Are replacement filters easily available?
• What certifications, testing or performance information does the manufacturer provide?

The last two points are particularly important because a purifier is not a one-time purchase. You will eventually need filters, servicing or replacement parts. A model that looks affordable at the time of purchase can become expensive if consumables are costly or difficult to source.

Are you paying for features your water doesn't need?

This is where it is easy to get carried away. Modern purifiers can come with mineralisers, alkaline cartridges, copper features, UV-LED systems, digital displays, filter-life indicators and connected monitoring.

Some features can be useful. But a long feature list shouldn't become a substitute for understanding the water itself.

• If your water has a specific problem that a particular technology addresses, that feature can have a clear purpose.
• If it doesn't, you may simply be paying for something that sounds impressive on the product page.

The same rule applies to purification stages: more isn't automatically better if the additional stages don't address a problem you actually have.

What will a water purifier cost after you buy it?

The purchase price is only one part of the calculation.

• For an RO system, factor in replacement filters and membranes, servicing, electricity and the water rejected during the purification process.
• Even among RO purifiers, water recovery can differ between systems and operating conditions.

So when comparing two models, don't just compare ₹10,000 with ₹15,000. Compare what you are likely to spend over the entire period you expect to use the purifier.

A cheaper purifier isn't necessarily cheaper to own.

So, which purifier should you buy?

There is no universal answer. If testing shows that your water has high dissolved solids or specific dissolved contaminants that RO is designed to reduce, an RO purifier can make sense.

If your concern is different, another technology or a combination of technologies may be more appropriate. The important thing is to stop treating RO as the starting point.

Start with the water source. Check TDS if useful. Look beyond that number when necessary. Understand the problem and then choose the technology that addresses it.

Because when it comes to drinking water, the smartest purchase isn't necessarily the purifier with the most stages, the highest price or the longest list of features.

It is the one that solves the problem your water actually has.

Similar stories for you

10 best water purifiers for home: Clean, safe, and smart options for every kitchen

Best water purifiers with excellence of Copper + Alkaline: Experience the benefits of Copper and Alkaline in every drop

Top 5 best water purifiers in India ideal for Indian homes battling hard water and impurities for safe drinking

Disclaimer: Mint has an affiliate marketing partnership, which means we may get some commission on purchases you make through the retailer sites links provided. These partnerships do not influence our editorial content, which is free from any bias or marketing pitch. We strive to provide accurate and unbiased information to help you make informed decisions. We recommend verifying details with the retailer before making a purchase.