Rapid urbanization came up with a host of problems. Prominent among them, and something that affects all urban dwellers is poor water quality. And that makes water purifiers an imperative appliance in every home and office.

So how do you choose the right water purifier for your home? Do you need an RO water purifier? Or will a UV water purifier suffice? Let us explore in detail in this article.

First, we explain the various terms you may see when looking at a water purifier’s product description.

TDS

TDS refers to Total Dissolved Solids. These solids comprise calcium, magnesium, potassium, sulphates, nitrates, carbonates and so on. While some of them are beneficial in moderate quantities, some are not.

NGT suggests that if the water supply at your place has a TDS of less than 500 ppm, you generally don’t have to use an RO water purifier. But, you have to first analyse the water quality to understand if your water has any harmful TDS like nitrates, sulphates and fluorides. If any of these are in excess of 45 ppm each or if fluorides exceed 1 ppm, then, you need to invest in an RO water purifier, no matter the TDS.

Unfortunately, nitrate and sulphate levels are higher than 45 mg/L in many districts in states like Andhra Pradesh, Bihar, Delhi, Haryana, Himachal Pradesh, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Orissa, Punjab, Tamil Nadu, Rajasthan, West Bengal, and Uttar Pradesh. You could take a look at this resource from Central Ground Water Board to understand the quality of the water supply in your district.

RO

It refers to Reverse Osmosis, which is the only domestically available technology to eliminate TDS from water. No other membranes are capable of removing the dissolved solids in water.

RO purifiers work by using pressure to force water through RO membranes which have a pore size of 0.0001 microns. Impurities larger than this size are captured by the membrane. This not only includes dissolved solids, but also heavy metals, pathogens and other residues.

The main drawback of this technology is that it wastes a lot of water. It is because a large quantity of water with high levels of TDS will simply not permeate through the membrane. So, it gets discarded as wastewater. For every litre of purified water, around 3-4 litres are wasted depending on the TDS level of your input water.

MF

Microfiltration (MF) is also known as Ultra-Filtration (UF). Essentially, the technology is the same as RO. But, the pore size is higher at 0.01 to 0.1 micron. It can remove bacteria and other pathogens as well as heavy metals like lead, arsenic, iron etc. But, it can’t remove dissolved solids.

We have seen certain Youtubers saying MF is a hoax because why do you need to pass water through a membrane with a larger sieve when you have already passed it through one with a finer sieve. But it is factually incorrect to an extent because, in most purifiers, water purified through the RO membrane never goes into the UF membrane.

As mentioned in the previous section, RO water is devoid of dissolved solids. Its TDS is zero and hence unsuitable for consumption. So, the water purifier increases the TDS of the output water by mixing it with the raw input water. But this water would naturally be contaminated. So, it is passed through the UF membrane to get rid of the heavy metals and pathogens.

When you mix this water with the water passed through the RO membrane, you get water with an appropriate level of TDS that is absolutely pure.

If you are buying a water purifier with MTDS or TDS controller mechanism, ensure that it has MF/UF membrane. The diagram below explains how water flows through an RO water purifier with UF membrane.

Water flow through a RO Water Purifier with UF membrane

UV

Ultra Violet chamber kills bacteria, viruses and other pathogens to make water suitable for drinking. Almost all water purifiers have a UV chamber.

MTDS

Stands for Manual TDS controller. NGT ( National Green Tribunal) recommends setting the TDS of purified water to 150. But not everywhere is water with 150 ppm of TDS palatable. So, manufacturers have incorporated a mechanism to adjust the quantity of raw water being mixed with the RO water to alter the TDS to your desired level. Read more here.

How To Choose A Water Purifier?

Quality of Your Water Supply

choose water purifier- depends on water supply source

Whether you need an RO water purifier or an MF/UV water purifier depends to a great extent on the input source.

If you have a municipal water supply that usually has a TDS of less than 200, then, usually, you won’t need an RO water purifier. An MF/UV water purifier is usually enough. This ensures pathogens and any other heavy metal contamination from old pipelines are eliminated in your drinking water. The same applies if you have a river or surface-level water supply too.

But, if you have water supply from borewells, tankers and such multiple sources, you have to delve further to understand the composition of your water. If you have TDS higher than 500, then opt for an RO water purifier.

Else, check the water quality to see if nitrates, sulphates, fluorides and other dissolved solids are within permissible levels. If it is within permissible levels, opt for a UF- UV purifier. Or else use an RO water purifier.

Water Purification Filters

Gravity-Based Non-Electric Water Purifiers- They are ideal for homes that have their own well for water supply. These gravity-based water purifiers have a UF candle at the centre. It captures any debris/residue. It would be a good idea to boil this water before consumption as it doesn’t have a UV chamber.

Activated Carbon Filter- Activated Carbon filters are available in most water purifiers. It captures odour and other VOCs ( Volatile Organic Compounds) like chlorine. It is available in most UF+UV and RO water purifiers.

UF+ UV- As mentioned, you can use Ultra Filtration (UF) also known as Microfiltration (MF)with Ultra Violet(UV) if your water doesn’t have a high TDS level. It is ideal for well or municipal water supply.

RO+UF+UV- RO is needed if you have water with a TDS level higher than 500 or if contaminants like fluoride, nitrate and sulphate exceed permissible levels.

UF is needed if the water purifier has a TDS control mechanism also known as MTDS.

RO+ Mineralizer- Certain water purifiers increase the TDS of the RO water by adding necessary minerals using a mineralizer cartridge. The water is passed through different calcium and magnesium compounds to increase the mineral content. In such water purifiers, UF mechanism is not necessary as raw water is not mixed with RO water.

Sediment Filter- It is a good idea to opt for a sediment filter if you own an RO water purifier. Especially so, if you have frequent water supply disruptions. Frequent disruptions could lead to sediments deposited at the bottom of the main tank getting agitated and mixed into the water supply.

Sediment filter captures sand, mud and other heavier contaminants to reduce the burden on the other expensive RO and UF membranes. This also helps enhance the life of RO and UF membranes.

Water Purification Capacity

Once you have decided on the type of water purifier to buy, next you have to take a look at the water purification capacity to match the needs of your home.

Most RO water purifiers filter around 6-9 litres of water per hour and have a per-day throughput of 20-25 litres. They have a water tank with a 7-10 litre capacity. This is usually enough for a family with 4-7 members.

UF+UV water purifiers have a much higher capacity, purifying 10-15 litres of water per hour. They work on electricity. Models with and without water tanks are available. If you have frequent power disruption, opt for a model with a water tank.

Is RO Water Safe?

Of late, there are many contentions about the safety of RO water. Many people claim that RO water is not safe as it doesn’t have the necessary minerals. This is backed by research by WHO that claims drinking de-mineralized water could throw your body’s electrolyte balance off. On the flip side, drinking water with high TDS or water contaminated with nitrates and fluorides is more dangerous.

The best way is to prudently use RO water purifiers to maximize the benefits and minimize the dangers. Ideally, RO-purified water should ideally have a TDS level of 150. But, it is not always practical. So, check the palatability of your water and set the TDS level as high as possible. In most metros, you can set it to at least 50-60 without the water’s taste going off.

Other Features To Look For When Buying A Water Purifier

The very basic thing that you have to look for when buying a water purifier is the type of filters it has. And it has been described in detail in the above sections.

Other features that are good to have for a user-friendly experience are-

Indicators- Opt for water purifiers that have indicators alerting when the water is purifying, when it is ready and when the filters need to be changed. Takes out the guesswork!
Water Tank Capacity- Opt for water purifiers with at least a 7-litre tank capacity so that you always have sufficient water for all your needs.
Hot Water- Water purifiers from AO Smith have a built-in heater to supply water at 45 and 80 degrees Celsius. The water is not boiled. But, it is helpful for soaking pulses and having a quick sip of warm water. But a drawback is that they don’t work unless the power supply is on. Also, the tank has to be full in order to supply hot water.
Water Recovery System- RO Water purifiers from HUL and AO Smith have water recovery technology that helps reduce wastage. Kent has a system whereby the wastewater can be directed back to the overhead tank.

How Many Stages Should My Water Purifier Have?

Of late, you can see water purifiers with 7-10 or even more stages of water purification. Sometimes, it is a gimmick as people often believe the higher the better and charge a premium for it. But, remember that you have to change these filters and membranes on an annual basis. So, the maintenance cost will be higher.

If you see a model having both MTDS and mineralizer or additional filter like silver ion technology, they are in most cases unnecessary. Ideally, an RO water purifier should have RO membrane, UF membrane, MTDS or TDS controller, UV chamber and carbon filter.

Should I Opt For Water Purifier With Copper Technology?

Many manufacturers sell water purifiers that infuse copper ions into the water. They don’t provide figures to indicate the level of copper infused into the water. You don’t have to worry about copper toxicity as it happens only when daily copper intake exceeds 10,000 ppm, which is pretty rare.

But does it provide any benefit? Not really. Copper deficiencies are extremely rare. So drinking copper infused water wouldn’t really have any positive effects on your health.

In rural areas, people store water in copper vessels to purify it. And it is helpful. According to research, no bacteria could be recovered from water stored in copper vessels for 16 hours.

But, the water you get from the water purifier is already clean and devoid of any pathogens. So, infusing copper ions into water doesn’t really purify the water any further.

A few user reviews also say that copper-infused water from the purifiers did not taste good to them.

Considering the premium price tag and non-existential benefits claimed, it is wiser to opt for a regular water purifier rather than one with a copper filter.

With this, we hope to have cleared all the basic questions you have in mind while buying a water purifier. If you have any questions, let us know in the comments below.