Written by: Subhasish Adhikary

RO vs UV vs UF Water Purifiers – Which is the best?

Water is the driving force of nature.

To survive on this planet, water is a basic need – for humans, plants, and animals alike.

However, in today’s day and age, it is not wise to drink water without first purifying it.

Most water found on Earth is unfit for drinking, and even the small percent that was once safe is now mixed with pollutants due to human activity.

This is not a problem that can be ignored in the long run. In fact, water is essential for almost all human activity, from absorbing and carrying nutrients to the cells in our body to flushing out toxins and waste. 

Contaminated water could be a carrier of water-borne diseases like diarrhea, amoebiasis, or even trace amounts of toxins.

Substances like Arsenic, Lead, and MtBE when accumulated, may result in fatal complications including organ failure.

So, choosing a water purifier for your home is a crucial step towards ensuring safety and health for you and your family. Like most technology, the choices of water purifiers available in the market are abundant and confusing. 

There are three different types of water purifiers that you might have noticed in the market.

These are RO (Reverse Osmosis), UV (Ultra Violet), UF (Ultra-Filtration).

Each of these technologies functions slightly differently and hence has its own pros and cons which we will analyze in detail.

7 stage water purification method
7 stage water purification method

At the end of this article, you will be able to assess your needs and pick the right water purifier for you and your family.

Reverse Osmosis water purifier (RO):

You may have already heard about the term Osmosis which refers to the movement of a solvent across a semipermeable membrane, from low concentration to high concentration.

In Reverse Osmosis the opposite happens. That is, the liquid flows from high to low concentration through a semipermeable membrane when pressure is applied to it. The water is passed through the inlet and several layers of filtering.

Reverse Osmosis in water purifier diagram
Reverse Osmosis in water purifier diagram

The pre-filters remove larger particles – like dirt and contaminants that cause bad odor.

The next stage is Reverse Osmosis through the semipermeable membrane – where the microbes and dissolved salts and toxins are removed.

Most RO filters are equipped with a post-filter made of Carbon as well are a TDS controller or mineralizer.

RO filters are highly reliable filters that operate on this principle.

They contain a membrane with pores smaller than 0.0006 microns in diameter and can even capture dissolved contaminants – including dirt, salts, bacteria, virus, and heavy metal toxins.

RO purification process also removes healthy minerals in this process, which are replenished through a mineralizer. This results in clean and healthy drinking water, free from pollutants and toxins. 


  • RO filters provide healthy water- rich in minerals since they have a mineralizer. Other purifiers do not have this feature.
  • Due to the small pore size in the filter, it not only kills but also physically removes the dead bacteria and virus from the water. 
  • It removes harmful salts from the water, even when they are dissolved. This is particularly useful if the water available in your locality has high TDS.
  • There is a storage tank available in most RO filters, so in case of a power outage, there is no need to worry. 


TDS – Total dissolved salts refers to the amount of organic and inorganic materials dissolved in water. This includes ions, metals, and minerals – some of which may even be healthy. 300-500 ppm is the recommended TDS for safe and healthy drinking water. 


  • RO filtration runs on electricity. This contributes to the overall power consumption that is not ideal.
  • The unfit water is rejected and wasted in RO filtration. This loss of water resources is not environmentally friendly. 
  • Regular maintenance charges are a bit higher as compared to other filters.

Ultraviolet water purifier (UV)

The UV filter purifies water through ultraviolet rays, which are a form of electromagnetic radiation with a wavelength ranging from 10 to 400 nm.

The water is passed through an inlet into a chamber that contains a transparent quartz-glass sleeve. This wavelength is produced by a UV lamp placed inside the quartz glass and allows water to flow around it.

This ensures that electricity is isolated from the water. These UV rays penetrate and kill germs and microorganisms present in the water, and can purify the water up to 99%.

The proximity of this wavelength is enough to destroy the DNA of pathogens like bacteria and viruses, and they can no longer pose a threat or reproduce.

This killing of bacteria and viruses is often done by adding chemical disinfectants like Chlorine to water, which may leave behind some odor.

This is also not always safe to consume directly or even use for cooking.  

However, the dead microbes remain in the water – but are not harmful in any way. The water is often also passed through an additional filter to remove floating contaminants that may be present in the water.

This way no extra water is wasted and only pure water is obtained after filtration. 


  • UV filters act much quicker than others and can instantly provide purified water
  • There is not much maintenance to be done for this technology
  • The installation is simple and doesn’t require any special skill to set up


  • The filter requires electricity to power the UV lamp.
  • Although it kills the living organisms in the water – the bodies remain in the water
  • It cannot remove dissolved salt and toxins from the water
  • Over time the filter may lose its efficiency since there may be some deposits on the surface of the lamp. This may require a replacement of the lamp/chamber.
  • Cannot filter dirty water with high levels of suspended solid particles as efficiently, as they may block the UV rays from destroying the living organisms.

Ultra-Filtration water purifier (UF)

Ultra-filtration water purifiers are the only technology of the three that work without electricity. However, this is not to say that they aren’t as efficient as the others.

How Ultra-Filtration water purifier works
How Ultra-Filtration water purifier works

Similar to RO filtration, the UF purifiers also use a membrane to remove impurities from the water.

Most systems use a hollow fiber membrane that allows water to pass through it from inside to out, which increases surface area for filtration.

The pores on the membrane are 0.01 microns in diameter and can eliminate solid particles, dirt, and micro-organisms from the water.

To put this in perspective, the pores can help remove pollutants that are 5000 times smaller than a human hair.

This filtration process involves no additional elements, and even the pressure exerted from the water is hydrostatic due to the pull of gravity.

The impurities and contaminants are caught in the filters and removed from the water.

However, this cannot suffice in cases where the water has high TDS levels. The dissolved salts and toxins, including poisonous substances like Arsenic and Lead, cannot be removed by UF purifiers alone.

Most water supplied to residential areas do not often have these heavy metals dissolved in it. So, UF purifiers are sufficient in most cases. 


  • The overall filtration process is cheaper- both for initial investment, and over the long term in terms of maintenance.
  • It can clear and purify even muddy water.
  • UF purifiers do not utilize any electricity or waste any water. This is both eco-friendly and easy to use.
  • These purifiers are lightweight and easy to use on the go.
  • No need for any installation, it is ready to use out of the box.


  • They do not remove dissolved toxins that may be present in the water.
  • Not useful to stabilize the TDS of water since it can neither remove harmful salts nor replenish healthy minerals.

Check out: Best RO+UV+UF Water Purifiers in India

RO vs UV vs UF Water Purifiers – Which one is best for you?

You may now have understood the principle on which each of the technology works and the advantages and drawbacks. Let us now draw a direct comparison between the three types we have seen so far.

RO vs UV vs UF Water Purifiers - Detailed Comparison
RO vs UV vs UF Water Purifiers – Detail Comparison

You may be interested in: Alkaline Water Purifiers: All You Need To Know

To pick the right purifying technology, you will have to consider the following:

TDS of your water

It is crucial to either find out about or manually test the TDS levels in the water in your locality.

Level of TDS in water measured in ppm
Level of TDS in water measured in ppm

This will help you understand your need for a filter that can remove the dissolved salts and toxins. If the levels are above the recommendation (300-500), then you may be best off with a RO filter.

On the off chance that the TDS levels are lower (100-150), you might still want to invest in an RO filter. This is because although the water may be safe to drink, it lacks the healthy minerals found in natural water that benefit you.

These minerals are replenished through the mineralizer in the RO purifier.

This test can be done by purchasing a digital TDS meter, or by simply enquiring from the local municipality that supplies the water.

Check out these TDS meter for water testing in home that you can buy online.

Digital LCD TDS Meter Waterfilter Tester for measuring TDS3/TEMP/PPM

KONVIO NEER Digital LCD TDS Meter for RO Water Filter Tester & Measuring

Chemical Dissolvents

If you live in an industrial/agricultural area there may be harmful toxins in your water that need to be filtered before usage.

The source of these chemicals may be from industrial discharge or pesticides which may be lethal if consumed over a long period of time.

This may require a combination of purifiers that implements both RO and UF techniques.

This will clear the water of all dissolvents as well as purify the smallest impurities from the water.  

Electricity availability

If you experience frequent power cuts or are looking for a filter that you can move around without the need for a power outlet, the UF filter might be the right option for you.

This is particularly true if you live in areas that are prone to earthquakes or other natural calamities since having readily available purified water is a necessity. 

The turbidity of the water

If the water supplied to your house is not clean and looks like it might have a lot of dirt/mud, it means that the UV filter will not work as well.

Depending on the level of solid impurities you might have to pick either a combination of RO/UV and UF or a standalone UF purifier.

This will ensure that the water is cleaned of visible and invisible pollutants.As discussed earlier, dirty water reduces the efficiency of the UV filters. 

For further reading: Essential Water Purifier Buying Guide for Home


This guide on the different water purifying technologies has hopefully helped you assess your need as well as the options available.

If you are still unsure, it might be best to go with an RO and UF combination (along with a mineralizer/TDS controller). The combination of both offer pure water free from any impurities and ensures that the healthy minerals are present in the water you drink.

Several brands offer purifiers of various technologies in the market.

Once you decide what you want, the choice is much easier, and you can start drinking clean, safe, and healthy water almost immediately!

Photo of author

Subhasish Adhikary

I'm constantly in search of the latest gadgets & technology news that I can share with you. In my meantime, I blog on topics ranging from digital marketing, online business, startups to tech gadgets.


Top 9 Best Mattress for Good Sleep in India

Best Indian Web Series on Netflix