Water Purifier – RO vs UV vs UF

Drinking pure and safe water is an important aspect of day to day to living. Impure water containing pathogens can give way to serious health problems, therefore, it becomes very important to make sure that the water you drink is safe and healthy.

It is crucial that you choose the best water purifier to save yourself from harmful water borne disease causing particles like bacteria, virus, pesticides, harmful chemicals, heavy metal impurities etc. The ground water pollution in India is a major problem right now, due to which the natural water in rivers, lakes, ponds, reservoirs is no longer pure. Hence, it is almost certain that the water coming to your house has some form of impurities.

Choosing the correct water purifier isn’t as simple a task as it sounds like. There are various technologies available in the market for water purifiers, and people generally end up being confused between RO vs UV vs UF water purifiers. If you are also trying to understand the differences between these technologies, then you have landed on the most definitive and complete guide for this.

Reverse Osmosis (RO), Ultra Violet Filtration (UV), and Ultra Filtration (UF) are the three most widely used purification technologies in water purifiers in India.

All of these technologies have their own pros and cons and we shall discuss in detail each one of those. We will also make a detailed comparison between these technologies and help you decide which one is right for you.

Before we delve deeper into the water purification technologies, it is important to understand the concept of TDS of water and how it is calculated. You can check out this article for more details on water TDS (Total Dissolved Solids)

RO vs UV vs UF Water Purifiers

The following table should provide high level key differences between RO vs UV vs UF water purifiers.

RO Water PurifiersUV Water PurifiersUF Water Purifiers
Needs electricity to operate
Kills bacteria and Viruses present in Water
Removes dead bacteria and Virus from water
Removes Dissolved Salts and toxic elements
Works with Turbid Water

Reverse Osmosis Water Purifier (RO)

RO water purification is the most advanced and reliable water purification technology. It removes the impurities from water using the Reverse Osmosis technology. Reverse Osmosis uses a semi permeable membrane having very small pore size.

When the water is passed through the membrane using pressure, the contaminants having larger size compared to water are left behind, and the water passes through the membrane. Hence, the resultant water is absolutely pure and doesn’t contain any dissolved impurities.

How does an RO water purifier work?

Osmosis is a natural process in which the water moves from a region of low density to high density. In Reverse Osmosis, external pressure is used to overcome the osmotic pressure and the water is forced to flow from the high density region to a low density region.

As we have already discussed, the RO water purification technology uses a semi permeable membrane. The membrane has a very tiny pore size of 0.0006 microns. Hence, when the pressure is applied against the semi permeable membrane, only the water is able to pass through the membrane and the impurities having a large molecule size are left behind.

Reverse Osmosis Water Purification

This process removes all the dissolved impurities including mud, salts, bacteria and viruses. Even the other heavy metal impurities like lead, arsenic, calcium. fluorides etc. are completely removed as well.

It should however be noted that the RO water purification in addition to removing dissolved impurities, also removes essential minerals from the water. Hence, the RO filters have to be used in conjunction with TDS controller or mineralizer.

Advantages of RO Water Purifiers

Removes all type of dissolved impurities including bacteria, viruses, pesticides, chemicals, heavy metal impurities etc.
RO water purification is the most advanced and reliable water purification technology which can provide 100% purified water.
Modern day RO water purifiers come with TDS controller and/or mineralizers which are capable of replenishing the lost essential minerals.
RO water purifiers are most capable of purifying hard water.

Disadvantages of RO Water Purifiers

RO water purifiers waste a lot of water. For every 1 liter of purified water it wastes around 3 liters of water. Therefore, RO water purifiers are not very environment friendly.
For RO water purifiers electricity is must, they can not operate when the electricity is gone.
In comparison to other water purification technologies, the maintenance cost is relatively high.
in addition to removing dissolved impurities, RO filters also remove essential minerals from water. So, they require a TDS controller or mineralizer and can not work alone.

Ultra Violet Water Purifier (UV)

Ultra Violet water purification technology relies on the germicidal Ultra Violet radiations to kills bacteria and viruses which are present in water.

UV purification is often used in conjunction with RO filtration to kill the residual bacteria and viruses present in water. Similar to RO, the UV purification also uses electricity to function, however, this process is completely chemical free.

How does a UV water purifier work?

UV Water Purification

The UV water purification filter has a UV bulb attached to the chamber, which produces strong germicidal Ultra Violet radiations. As the water passes through the chamber, the UV radiations penetrates through the bacteria and viruses, thus destroying these disease causing pathogens.

UV water purification is capable of destroying 99.99% of disease causing pathogens without altering the taste and odor of water. However, UV water purification in itself is not sufficient for treating dirty water. Reason being, it can only kill the dissolved bacteria and viruses and is unable to remove turbidity, chemicals, pesticides, and heavy metals. For this reason, UV water purification is often used in combination with RO water purification.

Advantages of UV Water Purifiers

It is proven to kill 99.99% of disease causing bacteria and viruses inside the water.
UV water purification doesn’t use any chemicals for water treatment, and is environment friendly and healthy method for purification.
UV water purifiers use UV radiation, and hence they do not alter the odor or taste of water.
Since, it uses only a UV bulb for filtration, it is usually low maintenance compared to the RO water filters.

Disadvantages of UV Water Purifiers

UV water purifiers can not remove dissolved turbidity, chemicals, pesticides, metal impurities like arsenic, lead, fluoride etc.
Killed germs like bacteria and viruses are not removed from water.
Similar to RO water purifiers, the UV purifiers can not operate without electricity.
UV water purifiers have to be used in conjunction with other water purification technologies like RO filtration, and are ineffective when used in isolation to other technologies.
Suspended impurities can sometimes affect UV performance, so that the UV rays are unable to efficiently reach the bacteria and viruses to kill them.

Ultra Filtration Water Purifier (UF)

The UF water purification technology works somewhat similar to the RO water purification technology. However, in case of Ultra Filtration the membrane pore size is much bigger compared to the RO filter.

Ultra Filtration

Also, in case of UF the hydrostatic force of water is used to force the water across the semi-permeable membrane.

Ultra Filtration uses a fiber membrane which has a pore size of 0.02 microns. As the water passes through the membrane, the harmful bacteria and viruses are unable to pass through the membrane. Other suspended particles including turbidity and contaminants which have size larger than the membrane size are also unable to pass through and are filtered out.

It might seem logical that the UF filtration might be the best option for water purification, but that is not true. With the increasing levels of ground water pollution due to the industrial wastes, pesticides contamination etc., the amount of heavy metal contamination in water has significantly increased. This leads to the presence of impurities like lead, arsenic, cadmium, mercury, fluorides etc. in drinking water.

Now, since the pore size of membrane for UF filters is larger, they are unable to filter out the dissolved toxins like lead, mercury, cadmium etc. from the drinking water. Hence, the UF water purifiers can seldom be used alone and have to be combined with the RO water purifiers.

Advantages of UF Water Purifiers

UF filtration is a very cost effective option. It doesn’t require electricity to operate, and uses the gravity to force the water across the membrane.
The UF water purifiers are effective is removing the mud and turbidity from water and that too without having to use any electricity.
UF purifiers are capable of removing the dead bacteria and viruses from the water unlike the UV water purifiers.
UF water purifiers are very environment friendly option because they do not waste any water during purification and they don’t even need electricity to operate.

Disadvantages of UF Water Purifiers

The biggest disadvantage of UF water purifiers is that due to the large pore size of membrane, they are incapable of removing dissolved metal impurities like lead, mercury, cadmium etc. from the drinking water. Due to this, they have to be used in conjunction with the RO water purifiers.

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

At this point, you should have a clear idea about the different water purification technologies and how they work. The next important question is how to choose the best water purifier which is suitable for the input water at your home?

RO vs UV vs UF

In order to answer this question, the first thing you should do is, test the TDS of input water at home. To understand, how to check TDS of water, you can check out this article – How to check TDS of water?

This table should then provide you good reference data in order to decide on the water purification technology are needed based on the TDS of water.

TDS ValueTurbid Water Bacteria & VirusesIdeal Purifier
Below 300 PPMUF Water Purifier – sufficient for remving turbidity
Below 300 PPMUV Water Purifier – sufficient to kill bacteria & viruses
Below 300 PPMUV + UF water Purifier – UF is required to remove turbidity
Over 300 PPMRO Water Purifier + TDS controller/Mineralizer
Over 300 PPMRO + UV Purifier + TDS controller/Mineralizer
Over 300 PPMRO + UV +UF Purifier + TDS controller/Mineralizer

It should be noted that the above table is only indicative, and works well for most of the cases. You might have water TDS which is less than 300 PPM, but the water might have metal impurities if you stay close to industries. So, in that case you should be using a RO water purifier in order to eliminate the metal impurities.

It is wise to do a chemical test on the input water in order to determine if there metal impurities present in water.

Lastly, in case you are still confused while buying the best water purifier, it is always safe to pick up a RO+UV+UF water purifier with TDS controller. RO, UV, and UF in combination should be able to remove all the impurities in water.


These days you can get a combination of RO+UV+UF water purifier at very affordable prices in India. A combination of the three water purification technology is best and works for all India homes. It is therefore best to go with a water purifiers which use RO+UV+UF for doing water purification.

However, if you want to save up on the RO water filter, and use only UV UF, then make sure that the TDS of input water is less than 300 PPM and it doesn’t contain any metal impurities.

If you have any further queries, feel free to drop a comment below and our team will get back to you as soon as possible.

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