What is RO, UV, UF, and TDS? All you Need to Know!

ro vs uv vs uf

What is the first thing that comes to your mind when you think of water purifiers? Probably, the first memory that most of us would have is that of a simple cylindrical filter with a mesh partition through which the dirt in the water was filtered out.

Truth be told, this arrangement used to function pretty well, but with time, the pollution has made the tap water dirtier and unwholesome. Needless to say, when it comes to ensuring access to clean and pure drinking water, we don’t want to take any chances at all.

This has led to the introduction of a range of water filtration technologies. The choices are such that it becomes quite a daunting task to pick the right model of water filter.

Are you sailing in the same boat, and don’t clearly know the difference between different water filtration technologies? Well, if that’s the case, let us help you out!

What is an RO filter?

RO is short for Reverse Osmosis and is one of the foolproof ways of distilling and purifying water. An RO filter comes equipped with a technology such that when you put water in the filter, it immediately increases the water pressure through a pump motor and then passes that water through the actual RO membrane before giving out the pure water through the outlet.

This RO membrane is semi-permeable in nature and allows only clean water to filter through. This way, the membrane retains all the impurities such as sand, dust, bacteria, virus and even dissolved solids.

RO filter – Pros and Cons


  • Water purifiers which distill water through RO technology are the most popular models in the market due to their effectiveness in purifying the water completely.
  • They are capable of eliminating dissolved salts in natural groundwater and are a perfect pick for coastal areas or areas which have mining fields nearby.


  • One big disadvantage of an RO purifier is that it leaves a lot of dirty water as residue. If you put in 3 liters of water into the purifier for distillation, the final output of pure water will be only 1 liter while the rest will be rejected as dirty water. This may be a problem in areas where there is a water shortage. However, the dirty water is still clean enough to be used for other household chores.
  • RO filters also consume a lot of electricity and are therefore responsible for driving up the cost of electricity bill, especially in rural areas or in areas where electricity is expensive.

Also, some RO purifiers are not equipped with desalination and end up eliminating even the necessary minerals in the water along with the harmful salts. To avoid this, it is recommended that you buy an RO water purifier of a reputed brand.

What is a UV filter?

Ultra Violet rays is a term that most of must have heard in connection with the environment protection initiatives. These rays that are emitted by the sun are harmful to all living beings including humans, animals, and plants.

In a UV filter, these rays are used in a concentrated way to kill the bacteria and virus present in the water. The best part about this filter is that it does not have a separate pump motor to increase the water pressure but can work on the pressure created by the normal tap.

UV Filter – Pros and Cons


  • The biggest advantage of the UV filter is that it is the most effective technology for killing off all the disease-causing bacteria and germs. If you are using a UV filter at your home, your chances of contracting a waterborne disease because of the water you are consuming at home are 100% eliminated.
  • Moreover, UV technology is also considered much more eco-friendly as it does not make use of any chemicals to distill the water but simply achieves its goal by the strong UV rays.


  • UV filter also suffers from the disadvantage of having absolutely no means to filter out the mud, dirt and dissolved salts from the water. As such, it is suitable only for use as a purification system to rid the water of harmful bacteria and germs but not as a filter for the overall cleanliness of the water.

What is a UF Filter?

The Ultra Filter or the UF technology is the latest to jump on to the water filter bandwagon along with RO and UV water filtration technologies and has gained a lot of popularity among the families living in urban areas.

In a UF filter, the water is passed through a membrane consisting of microscopic filtering holes which hold back the dirt and mud in the water along with various bacteria, virus, and other harmful micro-organisms. The water is completely purified of any disease-causing substances and is completely safe for drinking.

This UF filter proves to be quite effective in urban areas where even tap water is generally clean of dirt and salts but may have virus and bacteria.

UF Filter – Pros and Cons


  • A unique feature of a UF filter is that it is capable of running without electricity. Unlike the RO filter, it does not need a special pump motor to increase the water pressure.
  • Moreover, unlike the UV filter, it does not need electric power to generate any rays. UF filter is one of the few filters with very low maintenance costs and is also extremely long-lasting.


  • One disadvantage associated with the UF filter is that though it has a filtering porous membrane, the bigger sized filtering holes are not capable of filtering the dissolved salts which are even more microscopic than the bacteria and virus. Therefore, this filter is recommended for use only if the water you are putting in the filter is already pure from harmful salts and minerals.

What is TDS?

TDS or Total Dissolved Salts is a term which you will frequently come across when researching for water filter technologies. Though it is not a filtering technology in itself, it is nevertheless essential to know what TDS is and how it affects the water that we are drinking.

Total Dissolved Salts are those naturally occurring salts in groundwater that are more than 2 microns in size. These salts generally get interspersed in the otherwise pure groundwater because of excessive use of chemicals in the form of pesticides, insecticides and even industrial waste which may percolate down into the ground.

Needless to say, these harmful chemicals make the water impure and may adversely affect the health of a person if taken in excessive quantities over a prolonged period.

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What are the Acceptable TDS Levels?

It is a fact that you cannot get rid of all the TDS present in the water. If you are using an RO filter, you will be assured of fairly pure water free of TDS. However, excessive filtration without a desalination technology can also strip the water of its natural minerals. Keeping this in mind, the World Health Organization has come up with data on what the acceptable levels of TDS are.

TDS are measured in milligrams per unit of water or mg/L. According to WHO’s studies, water with 150-300 mg/L of TDS is considered safe for drinking. 300 – 500 mg/L is also considered as a fair quantity and this water quality is also potable.

However, water with 600-900 mg/L of TDS is considered of extremely poor quality and is not recommended for drinking. If the water has a TDS above 900 mg/L, it should be rejected outright and not even considered for filtration.

RO vs. UV vs. UF

Now that you have some idea about how these technologies work and what their individual advantages and disadvantages are, you will definitely be in a better position to decide which one suits your preference. Here is a quick comparison between these three water filtration technologies to help you in coming to the right decision.

The RO is by far the most effective water filtration technology as it accomplishes filtration of the TDS along with the bacteria, virus and other sediments. In its comparison, both UV and UF fall short when it comes to purifying the water of TDS.

On the other hand, RO wastes a lot of water and also uses up a lot of electricity in its operation. As compared to that, UV and UF filters are much more efficient and are also faster in completing the distillation. RO filters are also high maintenance and require regular servicing.

Our recommendation is that you should first find out the quality of water that you are getting in your tap. If the TDS concentration is anyway low in the tap water itself and falls within the safe range set by WHO, you do not need to get an RO filter.

In most urban households, a UV or UF filter works just fine because the groundwater or tap water has very moderate TDS levels which do not cause any harm to the health of a person.

If you are still in doubt, you may also choose to go for a water filter which uses a combination of filtration technologies. There are even some models which use all three technologies in their distillation system.

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These models are slightly more expensive than regular water filters but are nevertheless quite effective so that you can be absolutely free from worry regarding the quality of your drinking water.

Additional Things to Keep in Mind While Choosing a Water Filter

All the three technologies for water filters i.e. RO, UV, and UF are quite popular in the market. Irrespective of which water filter you choose to go for, you should always buy the product of a reputed brand. Water filters are installed in each home for the safe health of its inhabitants and it does not work to scrimp on the quality of such a product just to save a few bucks.

Here are a few additional points to take care of:

Free installation and frequent servicing

The second aspect to keep in mind while buying a water purifier is to make sure that the company is offering free installation of the purifier in your home and at least one free after sales service. Water purifiers which use RO technology need frequent servicing to keep their motor running smoothly.

Effective cooling system

You should also ensure that an RO purifier has an effective cooling system so that the motor does not need to be changed frequently. UV and UF filters also need regular cleaning and servicing so that their filtration capabilities are not compromised.


The storage capacity of the water purifier will also have to be chosen by you according to the number of people who will be using it. You can also look for quality certifications from ISI and NSF on the models.

Last but not the least, it is highly recommended that you make an informed choice and do not blindly pick the first water purifier that you come across. Be sure of what your needs are and choose a water purifier accordingly.

Wrapping Up

We hope this article would have helped you in understanding the basic glossary related to the water filtration technologies. Got any query? Write to us in the comments below.


I Like to do proper research before making any Buying Decision, and that's why I made this blog to help you guys.

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