RO (Reverse Osmosis) water purifiers have become very popular in India. Because RO Water Purifiers are great at getting rid of water hardness, turbidity, and harmful micro-organism, people just rushed to buy these water purifiers even if the TDS in source water at their home was much lower than the recommended level of 500 mg/litre. With the result, many people ended up drinking water that was too low in TDS (dissolved minerals), acidic, and often tasteless.

And its not just about the taste, it actually is harmful to drink de-mineralized water which is acidic in nature and may result in digestion problems, weaker bones and other mineral deficiencies.

To fix this problem, RO manufactures came up with two solutions. Some started using a TDS controller and other started using an alkaline mineral cartridge to add minerals back to the RO purified water.

In this article we will discuss the pros and cons of these two methods and also know about the ideal TDS in RO water.

Lets Start..

TDS Controller Vs Mineralizer - Recommended TDS in RO Water Click To Tweet

Reverse Osmosis – What is It?

Reverse osmosis (RO) is a water purification technology that uses pressure to pass source water through a semi-permeable membrane with pores small enough to pass pure water through but rejecting dissolved salts (ions) and impurities like bacteria and virus.

While there are other methods of purifying water (like UV rays) that get rid of all microorganisms like bacteria and virus, but there is no other method available to get rid of dissolved salts (TDS) in the water.

 So, it is the requirement to reduce TDS or heavy metals in water, which makes the use of RO filtration necessary for water purification. 

What is TDS?

TDS or total dissolved solids is the amount of dissolved organic and inorganic impurities in water. This includes calcium, magnesium, potassium, sodium, carbonates, nitrates, bicarbonates, chlorides, sulfates, and a small amount of organic matter such as leaves, silt, and plankton. In some areas (usually heavily polluted), the TDS in water includes toxic ions of heavy metals such as lead, nitrate, cadmium, and arsenic.

TDS Source

The composition of TDS in water will depend on the composition of rocks/soil in the area, presence of industries, sewage/waste water discharge, quality of river water (if present), air pollution from industries and automobiles (resulting in acidic rain), agricultural runoff (chemicals from fertilisers and pesticides), urban runoff, and various other factors.

Is High TDS Always Harmful?

High TDS by itself isn’t necessarily unhealthy. However, high TDS levels are frequently accompanied by concentrations of other substances (usually the heavy metals like arsenic, chromium, cadmium, mercury, lead, and a few others) that are harmful to health.

At the same time if you live in an area where there is no industrial waste discharged into soil or water bodies, and no one uses synthetic pesticides or fertilisers in their agricultural farms, then the water available in such an area would normally be very healthy. Even if the TDS count of underground water in such an area reaches up to 1200 mg/litre, it would still be safe for humans.

All it will have is useful minerals and bicarbonates in the water which are not harmful and our bodies are naturally able to handle such natural mineral water. There can be some exceptions of-course.

High TDS is a problem when there are toxic chemicals present in the source water. Or when the TDS is greater than 1200 mg/litre. Such water is then unpalatable.

Recommended Levels of TDS in RO Water

Ideal TDS in Drinking Water

According to the EPA as well as the Bureau of Indian Standards (BIS), the ideal TDS in drinking water should be less than or equal to 500 mg / litre.

Taste of ​Water with ​Different TDS ​Concentrations

High levels of TDS in drinking-water may have a certain objectionable taste because of salts. At the WHO, a panels of water tasters rated the taste of water in relation to the TDS level. This is what they observed:

Level of TDS (​mg/​litre) Rating
Less than 300 Excellent Taste
300 – 600 Good Taste
600 – 900 Fair Taste
900 – 1,200 Poor Taste
Above 1,200 Unacceptable Taste

Recommended TDS in RO Water

RO water purifiers that come with a TDS controller gives you the ability of controlling the TDS of output water. While there is no guideline about it from the government, we can take a clue from the studies done by the WHO.

WHO suggests that TDS in drinking water should never go below 30 ppm or else its a risk to your health. Another WHO study as quoted above, found that water tastes best when the TDS is under 300 mg/litre.

From all this, we can conclude that the ideal TDS of drinking water should be anywhere between 50 to 300 mg/litre. If you don’t want a range but a single number, then take the average and it would be around 150 mg/litre.

However, if the source water at your home is contaminated with heavy metals, then it may be better to keep TDS level at 90 mg/litre. This is because TDS controller will add minerals from the source water and it will include every mineral present in the source water in small quantity.

 If you ask us, we would suggest to keep the TDS levels of water between 90 – 150 mg/litre (ppm) depending on the pollution level in your area. 

If you want to be sure, then you should get the source water tested by a government water supply agency or laboratory. Alternatively, you can test the water at home using the products listed below. The test you do at home are not accurate but they give you an idea.

Why We Need a TDS Controller or Mineral Cartridge

RO water purifiers reduces the TDS of water by 90-95%. When this kind of purifier is used with water that has TDS between 100 to 500 mg/litre, then the output water is extremely low in TDS. It can have a TDS of 10 mg to 50 mg/litre. Such water may be harmful for health and may even be acidic in nature. Your body will have to work extra to fix its mineral contents and its PH.

The National Green Tribunal of India, has recommended Govt of India to ban RO water purifiers in areas where TDS in source water is less than 500 mg/litre for this very reason and for the reason that RO wastes too much of water in the process of purification. This shows that the problem is real and if we use a RO water purifier, we must constantly check the TDS in output water and adjust TDS using TDS controller or by changing the mineral cartridge.

TDS Controller/Adjuster

TDS Controller

TDS controller is a screw-based device that controls the level of salts in the purified output water. It works as a bypass valve which takes a percentage (adjustable) of source water bypassing RO membrane to the output water, which is then filtered through a UF or carbon filter, and/or UV chamber. Number of filtration methods and the sequence used varies from model to model.

How does a TDS controller work?

The water going into the reverse osmosis filter is divided into 2 parts. One part goes into the RO membrane and undergoes RO purification. The second part of water does not go through the RO membrane. It goes through a UF membrane or a UV Chamber, depending on the RO specifications.

The output water would be a mixture of  water purified in Part 1 plus a small portion of Part 2 water. The mixture is controlled through a valve connected to the Part 2 assembly, thus controlling the TDS.

Advantages of TDS Controller

Flexibility: Having a RO water purifier gives you the flexibility of adjusting the TDS levels in output water as per your choice. You can set it to 150 mg/litre today and later if you change your mind, you can set it to any other limit without changing the water purifier. Also, if you want, you can close the water coming from part 2 completely and the output water would be 100% RO purified water.

Economical: TDS controller is a cheap device and costs around 100 rupees only. Further, it is a one time expense and you won’t need to change it for several years.

Natural: Because TDS controller adds minerals from the source input water, it has a wide variety of minerals naturally present in the water.  Therefore this kind of water is more natural.

Enviornment Friendly: A RO water purifier fitted with TDS controller usually wastes less water in the purification process and hence is more efficient and enviornment friendly.

Disadvantages of TDS controller

Not 100% RO Purified Water: The output water from a RO water purifier with TDS controller is not 100% RO purified water. Because the TDS controller mixes a part of water that did not go through RO membrane to the output water, it will have all the minerals and chemicals present in it that were originally present in the input water, though in very-very smaller amount.

This is usually not a problem unless the source water is heavily polluted with heavy metals like lead, nitrate, cadmium, and arsenic. As long as the output water has these heavy metals under the safe limit, it would be safe to consume such a water.

Further, most of the RO purifiers with TDS controller come with an extra water filter (Usually a UF or UV cartridge) that purifies water in the final stage so that micro-organisms present in water that did not pass through RO membrane are killed.

Alkaline Mineral Cartridge

Mineral cartridge

Some RO water purifiers use an alkaline mineral cartridge to add minerals back in the purified water. A mineral cartridge typically contains several layers of different materials. These may include pelletized activated carbon, mineral balls, PH booster balls, antibacterial balls, ceramic balls, tourmaline balls, etc.

How does an Alkaline Mineral Cartridge work?

After the water has passed through the RO membrane, it is then made to pass through a mineral cartridge. During the process, it extracts minerals from the mineral balls present in the cartridge. Some cartridges come with PH booster balls and in that case, the PH of water improves and the water becomes alkaline.

The quality of mineral cartridge used is very important here as it would decide the variety of minerals that get added to the purified water. Some mineral cartridges also claim of providing additional benefits by energising water, and more.

Advantages of Alkaline Mineral Cartridge

Best Protection Against Heavy Metals: RO water purifiers with a mineral cartridge and no TDS controller offer the best protection against pollutants, pesticides, and heavy metals. It is because it provides 100% RO purified water and the additional minerals added come from the mineral cartridge that only contains healthy minerals like calcium and magnesium.

Disadvantages of Alkaline Mineral Cartridge

No control over TDS of output water: If your RO water purifier uses a mineral cartridge, then the output water TDS would depend on the TDS of source water and the quality of mineral cartridge.

The RO filtration would decrease TDS of purified water by 90 to 95%. A mineral cartridge would add 20mg/litre to 80mg/litre TDS to the purified water.

For example, if TDS of input water is 200mg/litre, the output water would have a TDS of 10 to 20mg/litre after passing through RO membrane. After passing through a mineralizer, it would have a TDS of 40 to 100 depending on the quality of mineral cartridge used.

If the mineral cartridge used is not very good, then the TDS of output water in this case would be just 30 or 40mg/litre which is unacceptable.

In any case, you will not be able to adjust the TDS as per your choice.

Recurring Cost: Mineral cartridge, would need to be replaced every 6 to 9 months depending on the usage. This adds to the annual cost of maintaining a RO water purifier.

TDS Controller Vs Alkaline Mineral Cartridge

TDS Controller Mineral Cartridge
Suitable for source water with TDS upto 1200 mg/litre and no or very low amount of heavy metals present in it. Suitable for source water with TDS up to 2000mg/litre.
Full control over TDS of output water No control over TDS of output water.
Economical and Enviornment Friendly Adds rupees 1000 to 2500 to the annual maintenance cost.

Top 3 RO Water Purifiers with a TDS Controller

Top 3 RO Water Purifiers with an Alkaline Mineral Cartridge

Looking for water purifiers in a certain budget? Check the following posts:


TDS controller and mineral cartridge both are good at increasing the TDS count in RO purified water. Which one you choose depends on your personal choice and also on the TDS count and presence of heavy metals in the source water.

We recommend RO with TDS Controller if the source water has TDS less than 1000mg/litre with negligible amount of heavy metals. For water with TDS upto 2000mg/litre, we recommend a RO purifier with mineral cartridge.

Riya Menon

Last update on 2022-05-18 / Images from Amazon

79 replies
  1. Ganeshkumar says:

    My bore well water tds level 1300 how to control

  2. Dipak pawar says:

    Very useful information about TDS controler and mineralieser .most of people don’t know which quality of water is better for health

  3. Raja sekhara Reddy says:

    Fantastic. I am very much impressed with the information you provided. Thankful to you.

  4. Ranjan Maganlal vaghela says:

    I suggest along with any water purifier purchase the TDS meter should come along with. Also insisting Service man should bring Tds meter n set TDS after service.

    • Lavanay says:

      Most of the technicians have a TDS Meter with them. But TDS can be set only in case the water purifier you’ve purchased has a TDS controller. If it has no TDS controller, then there is no way to set the TDS in output water.

  5. Inder Kumar Mangla says:

    Can we improve the quality of water purifiers ,which will act as auto set up that is as per requirement of TDS ( 1200mg/litre or 2000mg/ litre)
    and economically also.

  6. Chaitanya J says:

    Really appreciate all the information which has been gathered. Am really worried about low TDS in drinking water for us raw water TDS is 350-450 fluctuates and Output from RO has 20-30TDS levels. We get bore water in our society and I use a Aqua guard RO+UV water purifier any suggestions for improvement or increasing TDS without purchasing another RO water purifier.

    • Lavanay says:

      If the RO you have, comes with a TDS cotroller, then its possible to control TDS in output water. Otherwise, there is no way to improve TDS without purchasing a new machine.

  7. Rajiv Chopra says:

    Is there any relation between tds and ph values? Ph of more that 7 is alkaline water.
    What is the recommended ph of drinking water?
    Also what the recommended ORP of drinking water?

    • Lavanay says:

      Presense of TDS minerals in water increase its PH value.
      Ideal PH in drinking water is 7 to 7.99
      Ideal ORP in drinking water is around 200 to 350 mV. Non technical people need not think too much about it.

  8. Sumit says:

    Since tds controller helps to bring the tds to optimum level, does it thereby maintains the right pH level also? Or do we need to add a mineral cartridge separately for correcting the pH of treated water?

    • Lavanay says:

      Mineral cartridges increase PH of water by adding minerals. With TDS controller you do the same thing and thus the PH of water will be safe in both cases. However, if the mineral cartridge is not changed in time, the output water will have low TDS and acidic PH. There is no or very little chance of such a thing happening in case of TDS controller.

  9. Vipin Kumar says:

    Lavanay, Your information is helpful. One thing I am bothered is that in LG purifier they are adding minerals artificially from the mineral booster and not retaining the natural minerals of water like aquaguard.

    Are the artificial minerals not harmful for health?

    Can’t it sometimes add excess minerals than required and may harm body?

    • Lavanay says:

      As of now there is no scientific research available that implies that mineral cartridge can add excess minerals to water. So, we can conclude that it is safe.

  10. Rajesh says:

    I see that most RO purifiers+ TDS controllers where the process of purification is RO+ TDS controller+UV is defined as RO water +Tap water + UV= Drinking water. However, Eureka Forbes AquaSure Delight from Aquaguard (recommended by this website) (RO+UV+MTDS) and similar ones shows purification as TDS controller+ RO water+ UV i.e., TDS controller is before RO membrane. Is this correct? How are these different from Aquaguard Shield, Eureka Forbes Enhance etc.

    • Lavanay says:

      Hi Rajesh, It does not matter whether TDS controller is before the RO membrane or after it. If it is before RO membrane, it will restrict the amount of water that goes through the RO membrane. If it is after RO membrane, it will restrict the amount of RO purified water that is drawn out of it. In both the cases, it would be able to control the percentage of RO water that mixes with percentage of tap water. Finally, the water passes through the UV filter or any additional filters that differ from model to model. We should leave the designing part to the company’s engineers.

      Aquaguard Enhance has a premium look body.
      Aquaguard Shield comes with one extra part which is MP or membrane protector. It increases the life of RO membrane.

      • Rajesh says:

        I heard from this post TDS control is better than Mineral cartridge as in the later we cannot control the TDS of water as it is dependent on input TDS water. In this context Faber, Havells and other brands who are promoting Mineralizer are saying that in TDS controller type of RO water, we mix purified RO water with Tap water (cases where TDS controller is kept after RO purification) and in that cases we are not getting fully purified RO water. So, my question was is TDS controller before RO membrane (Like mentioned in Aquaguard Enhance etc.,) better to others design where TDS controller is after RO membrane (Kent RO Purifiers) and getting not purified RO water as mentioned by Faber, Havells etc.
        I am asking this as after RO membrane the TDS of water gets reduced by 90% and so we cannot maintain required TDS control if the TDS controller is before RO membrane. Also, some brands say the mineral cartridge in their RO purifier is kept before RO membrane, so in that case does the essential minerals (Magnesium, Calcium etc.,) required by human body, does it get blocked after water passes through RO membrane?

        • Lavanay says:

          There is no use of TDS controller if all water has to pass through the RO membrane. Similarly, it will be of no use if mineral cartridge is used before the RO membrane. I haven’t seen any water purifier that uses any of these two sequences. If you have made this assumption based on the title of products like say “Aquasure RO + TDS + UV”. Then I would like to clarify that such titles only mean that the purifier comes with these filter technologies. But not necessarily in the same sequence. Further, most RO water purifiers with TDS come with at least one more filter. If it uses UF filter, it is used to purify tap water and then it is mixed with RO water. If it uses UV filter, it is used to purify the water resulting after mixing tap water and RO water. So the final output water is neven unpurifier. It may not be completely RO purified, but rest assured, that it goes through some purification process before it flows out from the output water tap. Such water will be free of any harmful micro-organism but still contain some natural minerals and substances that are present in water in nature.

          • Delowar Delowar Hussain says:

            My boring water have tds level about 400.i using normal water filter with uv plus uv. Does it need me to with tds controller water purifier. Plz reply
            Also what is the option to buy.

          • Lavanay says:

            Your UV & UF water purifier is all you need. Cheers!

        • Rajesh says:

          Thanks for the clarification Lavanay. I did not go by the assumption in naming convention, I have seen in Amazon shopping site in stages of purification for Aquasure Delight that TDS controller is shown before RO membrane, so the query. Also in the pamphlets of Havells RO, they are mentioning that after RO membrane (pore size 0.0001 micron), TDS controller after RO membrane, impure water is mixed with Purified water (before UV and post Carbon filter), due to which some harmful minerals like Flouride, Arsenic, Lead etc. and new age pollutants, waste pesticide would not be cleaned fully as they do not pass through RO membrane. So, they recommend Mineralizers. So, the confusion is still there which type of RO water purifier to buy (10k one range or 20k range ones). Also are Bisleri, Kinley are mineral brands as they claim?

          • Lavanay says:

            Rajesh, As far as I know, Havells does not have a model with TDS controller. What they use after RO filteration would be mineralizer or taste enhancer. I see a listing on flipkart for Havells Max GHWRPMB015 that claims that it comes with TDS (not controller). When you check Havells website, you find that it has no TDS controller.

            Anyway, TDS controller can be used before or after RO membrane. If it is used before RO, it will divide water in two parts. One will pass through RO and other through UV. or it may be first mixed with purified water and then passed through UV filter.

            If TDS controller is used after RO membrane, it will adjust the amount of water that comes out of RO line and from the tap water line. Result and purpose is the same. But mineral cartridge can never be used before RO membrane.

            So, Yes Havells Water purifier will provide 100% RO purified water that would be free from all industrial pollutants. And It is also true that Aquasure Delight will not be 100% free from heavy metals/pollutants.

            Now, the choice between the two depends on the quality of input water at your home. Thats why we have emphasised to check the TDS in your input water. If it is between 500 to 900, and the water is been supplied by Jal Board, we recommend RO with TDS controller. If its above 900 mg/dl, then we recommend RO with mineralizer cartridge.

            Now, please note that a water purifier with TDS controller can also be used as 100% RO purifier. By adjusting the TDS controller, you can pass all water through RO membrane. But this is not recommended. The installation person will adjust the TDS controller in a way that the TDS in output water is between 50 to 90.

            When you use a TDS controller on water that has a little high TDS, then the amount of harmful chemicals left in purifier water will be negligible. Our bodies are designed to take care of some amount of impurities itself. Now the advantage here is that output water will have wide variety of natural minerals, and other substances. Its natural. In nature, you don’t get 100% purifier water or distilled water.

            When you use RO with mineralizer and alkaline/taste enhancer cartridge, it add only 2 of 4 minerals back to the purified water. The TDS in out put water in some cases could be as low as 30. Which may be harmful. Basically you can not control TDS in output water and it will be very low if you install this type of water purifier on a water supply that has TDS of 300 or lower.

            Bislery and Kinley are not mineral water. Bislery is purified water with Potassium and magnesium minerals added to it. Also this water is ozonated which may taste bad to some people. You can search the internet for pros and cons of ozonated water.

            We believe, while water purification is must in todays world, we should RO purify only when necessary. 100% clean is not good always. Read

            Finally, its upto your personal choice and different people go for different models based on their choices.

  11. Suresh AS says:

    We are making our life complicated day by day. First we get the water supplied by corporation, we mix it with stored dirty water in the lower level called sump. Then pass it to another dirty storage called over-head tank. They we purify it by RO. We again cry telling it it too pure. Let us add some minerals. (Let as add some impure water).
    If we get reasonable good drinkable water from corporation. All these complications are solved. All these RO business and water tank mafia business are closed.

    • Lavanay says:

      You’re right Suresh. As a kid I have drunk normal tap water at home, and in the school without much problem, but things have changed. Unless the Jal Boards/Corporation works hard to fix every leakage in the supply line, ensure regular cleaning of water tanks, and reduce TDS in water supply, the customers have no choice but to use water purifiers.

  12. T Tarunkumar Sharma says:

    I have an ro for fresh aqua india. An how much of tds rate drinking output water and wash output. I want to know that only thank you

  13. T Tarunkumar Sharma says:

    I test my tds output drinking water and see only 5 and wash output water get 108. For good health what is the accurate tds quality should get in my ro system.

    • Lavanay says:

      TDS in drinking water should never be under 30 mg/dl. Ideal TDS in my personal view should be between 60 to 120. If the RO purified water you are getting has a TDS of just 5, then it means that you don’t need a RO water purifier but a simple UV or UF water purifier would be enough to provide you safe drinking water.

  14. prasad says:

    Hi Lavanay, my bore well water has tds 130 to 150tds. It is near 300 meters to the pond, that is continuously filled with canal water. So can that pond will effect our bore well water tds levels. After this rainy season, will be there any difference in tds levels? I don’t know.

    Present bore will water is shown 138 tds level. It has little bit dust and clay, and the water taste is also not good(when compared with purified water cans, that we buy daily).
    In this situation, What is the best solution for me?

    • Lavanay says:

      Yes, the TDS of water will increase during rainy season but that is temporary. Most of the time its going to be under 200 mg/dl and so you should go for a good UV + UF water purifier like Kent Maxx. This water purifier will take care of any micro-organisms present in water as well as the turbidity (dust/clay)

      • Mani says:

        My bore water tds level is 520 after use auro my tds is 100 my filter is good condition or bad

        • Lavanay says:

          Generally, RO reduces TDS by 90%. However, if your purifier has a mineral cartridge and an alkaline cartridge, then its possible that TDS increases to 100. As such the TDS level of 100 is safe and as long as your water purifier have additional filter like UV or UF, you need not worry for safety of water.

  15. Gaurav Kulkarni says:

    Hi Lavanay, Can you suggest me a water purifier which can be bought on a safer side, as things are getting complex now-a-days. I am staying in Bhivpuri (nearby Karjat) in Maharashtra and I have bore well water for drinking purpose in my society. I don’t know what’s TDS level in the bore well water and how to calculate it or Will I get this information from my Builder or from where will I get this info about TDS levels in boring water which we use for consumption.

    I just need to know which is the best water purifier under Rs.10k! So that me & my family’s health is not at stake!

    Thanks in advance!

  16. Priyanka says:

    Tq for v.usefull information ..we get water from house wel,TDS of it’s water is 300.. I had Kent uv+uf+ro+TDS, recently I have told service men to disconnect ro from same existing filter n connect it directly to uf+uv.. is it ok n is water am getting safe and healthy?

  17. Sinod Kumar says:

    where I am living there is TDS around 3500(that is Bore water near to sea.)
    Kindly suggest to purchase new machine with what facilities.water has not been tested for heavy metals.

    • Lavanay says:

      TDS of 3500 is just too much for ordinary RO machines that are available in market to handle. You will need to contact a RO or water treatment company.

  18. Sachin Girdhar says:

    Hello there, very useful info. I just purchased LG 172EP RO + Mineral booster. Pre and post TDS is 900 and 820 respectively. I was very suspicious of high TDS in purified water but the tech says it is due to mineral booster cartridge. I doubt he is right. Do you think so too?

  19. Sandeep says:

    The tds level of water is 30 and i installed aquaguard
    ro +uv + mtds and water taste is bitter what shoud i do should i had to purchase only uv + uf water filter ??
    What to do with this filter,is it. Posdible to remove ro and use only uv +mtds.can filter changed ??

    • Lavanay says:

      When you reduce TDS levels in water so much, then it becomes acidic and bitter. Such water is not just bad in taste but it may also be harmful to your health. On the positive side, as your water purifier has a TDS controler, you can call the company technician and ask him to close the RO path completely, so that your water purifier works like a UV water purifier.

  20. Dibyendu Sekhar Maji says:

    My purifier gives tds of 56 and the borewell water tds is 770. Purifier has tds controller and antioxidant cartridge. Whether the purified water is safe for drinking. Please enlighten.

    • Lavanay says:

      Yes, it should be safe. Infact the company technicians usually set TDS in output water to 50 to 60 ppm. Because your water purifier has a TDS controller, you have the option to get it adjusted to your choice of TDS in output water. We recommend a TDS of 90 to 120 in purified water, but everyone has a different choice. There is no recommended TDS level by any health agency. The decision is entirely yours.

  21. VenugopalReddy. N says:

    I purchased Kent Supreme extra ZWW 11113(RO,UF,UV,TDS CONTROLLER,alkaline.8ph)from the product promises Iam not finding alkaline water in it. It shows from out side there is a post corbonplus alkaline media but I don’t know whether it is really for alkaline or not. When I checked with ph drops the out come water shows acidic(yellow in colour at 115 tds).my raw water tds is 900 and technician adjusted tds up to this adjusted tds is there any chance of getting heavy metals into final drinking water (as some water may not go through Ro membrane).if it is not suitable for me could you kindly suggest 100 percent RO with good quality alkaline mineral cartridge model in an ISI brand.

    • Lavanay says:

      Your input water has TDS 900. If you pass all water through RO, the TDS will reduce to 90 (approximately – based on expectation that RO membrane reduces TDS by 90%). Will this water have heavy metals in it? If the source water had heavy metals in it, then it would still be present in purified water but reduced in concentration by 90%.

      Similarly, by not passing some water through RO, the technician has increased TDS in output water to 115. This is slight increase in total TDS and this will also result in very slight increase in heavy metals in purified water, if it was present in source water at first place.

      There will be negligble difference of heavy metal concentrations in purified water in these two cases. That too only in case your source water had heavy metals.

      Regarding alkalinity of water, I haven’t tested it and therefore can’t comment. However, you should contact the company and ask why the output water is not alkaline. Also, knowing the exact PH value of purifier water would be better. Yellow color can mean very less acidic, which would be safe for humans.

  22. Rahul Vaidya says:

    Please tell me
    1.uv treated water in water purifier is good to consume for how long? As don’t have in tank uv like new models .

    2. at our house total water consumption is around 15 litres a day so we don’t keep our water purifier on always we switch it on two times a day to get collect 15 litres in outside copper vessel. As storing water for long in abs plastic tank is also not good is it right thing to do ?

    3.does silver impregnated activated post carbon is same like mineral cartridge / alkaline cartridge if not What the difference?

    4. if I remove ro membrane then does it have any affect on functioning overall.

    • Lavanay says:

      As long was you clean/service the water purifier as per recommendations of the manufacturer, the water in tank remains safe to consume.

      Yes, its a good idea to store water in copper bottles/vessels. Just make sure that the metal used is 99% pure copper as some manufacturers add other metals to copper before making the vessels and that can cause problems.

      Activated carbon cartridge is great at removing odour, and unwanted materials like chlorine from our drinking water. Silver impregnation carbon cartridge does the same plus it inhabits the bacteria growth. However, it would be more applicable in case of ordinary water purifiers and not RO purifiers. As in case of RO water purifier, no bacteria reaches post RO carbon filter.

      If you remove RO membrane, then if will definately affect the functioning of a water purifier. If you don’t want RO, purchase a UV/UF filter.

  23. Darshan says:

    Bore water tds is 950.adjusted tds for purified water is 120.(with tds controller)as the raw water doesnot pass 100 percent through Ro membrane will I get heavy metals in my purified water.what should I do for not getting heavy metals though we use tds controller.

    • Lavanay says:

      By using TDS controller, you have the option of passing 100% water through RO. This way you will get 100% RO purified water. However, I would not recommend that unless your water purifies also comes with a mineral cartridge.

      Also, we do not know if the source water has heavy metals in it or not. We need to know what heavymetals are present in water and in what concentration to give you a definative answer.

      Otherwise, based on assumptions, I would say that this purified water is most probably safe to drink. However, if you are not convinced, then change to a water purifier with mineral cartridge. If you are also concerned about alkalinity of water, then go for a water purifier that comes with additional alkaline cartridge. Some people also feel that plastic water storage tanks are no good and can release chemicals. If you feel so, then purchase a water purifier with stainless steel tank.

  24. Saritha says:

    We purchased kent purifier with tds control.raw water tds is 1000.can we adjust 100 percent Ro with tds controller(we may get 90tds of purified water)and add alkaline mineral cartridge to get around 120 tds with right ph level.we tried to get minerals naturally while increasing tds but not getting required ph levels.

    • Lavanay says:

      I don’t think it would be possible to adjust PH value of purified water using this model of water purifier. If you are concerned about the alkalinity of water, purchase a water purifier that comes with alkaline cartridge. Here are a few water that specialize in providing Alkaline water: KENT Supreme Extra 2020 (11113),
      Havells Max Alkaline, Faber Neutron Plus Alkaline RO + UV +UF + Copper Guard with pH Enhancer, and others.

  25. Yazh pure life says:

    I am from chennai. RO technician. This article speaking some truths.

    Lot of the companies having this adjuster but how it will be so safe? My suggestion is After the mixing of RO and TDS adjusted water we again process with the UV is the safe one.

    • Lavanay says:

      This is the case with most of the RO-TDS Adjuster type RO water purifiers.

  26. Sanjeeth says:

    TDS of our borewell water is around 470-520 currently. Assuming there are no heavy metals, can we go for a UV/UF filter without RO?

  27. Rajendran A says:

    Dear sir, I am a retired chemical engineer. I opened a RO purifier sales and service shop. Reading your article, question and answers i got clarity about tds controller vs alkaline / mineral cartridges uses. Thank you very much.

  28. Suresh Kumar says:

    My bore water is 300 tds using Kent RO+UV+UF and now tds is 90 is it good for health or not

  29. Rajdeep says:

    Biggest decision between tds controller and mineral cartridge would be that if the online water contains heavy metals, or other chemicals which can cause problems, in this case if you use tds controller, and you have less amount of heavy metals, still it is bad as it can accumulate in you and cause poisoning, cancer, in the long run, I don’t think source water tds should be considered in choosing a tds controller or a mineral cartridge, if you are concerned with tds then use low tds membrane or high tds membrane, to adjust the amount the tds you need, but I think it is always better to get your source water tested for heavy metals and chemicals, which may be hard in India, just to be safe I think if you are in a city like Delhi, Mumbai, Banglore, and all developed and crowded cities then use mineral cartridges, and check for the source water tds and then decide on using low tds membrane or high tds membrane to maintain the tds level.

    • Lavanay says:

      Yes, a lot of people think that way. But the fact is that Jal board’s or municipal water supply contains safe amount of TDS levels in 99% of cases. The solution is to get your water tested for heavy metals if you don’t trust your state government. Testing water for TDS is the minimum that everyone should do.

      If you use under ground water in polluted cities, then mineral cartilage is a must.

  30. Vijay says:

    Hi Madam,
    I am from Chennai(Chrompet) and staying in rented house, i am using canned drinking water(20L), when i was checked with TDS, it shows only 30, so i have decided to go water purifier, in my flat we are using the combination of Tanker lorry/municipal water/river water based on their availablity, when i was checked TDS it comes around 350-400. Now my queries are:
    1. Shall i go with UV & UF purifier is enough
    2. Or i need to go with RO with UV & UF with TDS controller (after seeing your articles i understand about the TDS controller and its usage)
    3. If its option 2 then can i go ahead with Kent grand* or any other brand is preferrable. Please sugges me…

    • Lavanay says:

      Yes, Kent Grand is a good pick in your case.

      • Viijay says:

        Thanks for your confirmation. If raw water of TDS is 350-450, what is the good level of TDS to set up for purifier water output.

        • Lavanay says:

          I personally prefer 50 to 90 PPM.

  31. Bharath says:

    Hi Lavanay,

    We have bought the water purifier recently, Later when I came to know about the TDS level and its usage.

    I have checked the TDS of tap water which came around 310 PPM.
    Water from the purifier has a TDS of only 20 PPM now.
    As 20 PPM is very less and not safe to drink. Will it be helpful if a TDS controller is used?
    If yes, What level should it be set? Could you please suggest?

    • Lavanay says:

      20 PPM is too low. Now that you have purchased a water purifier, you don’t have the option to install a TDS controller on it. The only possible way to improve this to 30+ is to get a good quality mineral cartilage installed if possible. Talk to the RO company support.

      • Bharath says:

        Thank you Lavanay for the quick response.

        I have purchased a purifier on a rental basis in Bangalore actually, So when I have checked with the purifier support team they have mentioned already water purifier is RO+UV+Mineralizer.

        They will provide a TDS controller it seems. So if they provide me such option to add what level should I ask them to set?

        • Lavanay says:

          Thats great. If they provide a TDS controller, then set the TDS of output water to between 50 to 90 PPM

  32. Shiva shetty says:


    You been great help to everyone and article is nicely drafted.

    I need some guidance. If you can help please.

    1. TDS level is 58 and it is municipal supply water
    2. I am little worried on such low TDS lev which I believe lack of minerals
    3. I don’t think RO is option for me, so what is the best water purifier which can do following

    A. Clean impurities such as clorine and other
    B. Add minerals back into water ?
    C. Kills germs in water

    Additional, I hear of purit coper. Review would be appreciated.

    Thank you so much for helping

      • Guru says:

        Dear Madam,
        I have Cauvery River water at my home in Bangalore.The TDS Is 140.Kindly clarify and give your suggestion for below points.
        1.I want to buy UF+UV from Aquaguard aura.
        What can be ORP of this water output.
        2.What’s the difference between mineral cartridge and alkaline cartridge
        3.Shall I but KYK or Kangen ionizer machine which gives ORP -400.Is Ionized water really need for human body.

        • Lavanay says:

          You are thinking too much. Just believe in the goodness of natural water. If you are getting natural Cauvery river water with TDS of only 140, then its amazing! Believe in your decision of purchasing the UF+UV water purifier and forget the rest.

  33. Surinder Marwaha says:

    Although I am not an engineer or deals in ro business in any way but because of my hobby to acquire knowledge from all sources, I have fully gone through the contents of the article and found these to be very informative and useful.

  34. Surinder Marwaha says:

    TDS of source water at my place is around 90-100 pm. I have ro installed in my house. Is it advisable to bypass the ro membrane to convert the ro into simple water purifier in this?

  35. Shiva shetty says:


    Thanks for the detail review. How is Eureka Forbes Aquaguard Aura 7L water purifier UV e-boiling+Ultra Filtration with Active Copper? Is this best to buy? Does coper thing really work or is this just gimmick? Also is it safe for coper ion ?

    • Lavanay says:

      Current medical research suggests that copper ions within a limit do not pose any threat. Because these copper RO water purifiers from Eureka and PureIT infuse copper at the time of water dispensation, the chances of overdose of copper are negligible. So, yes it should be safe.

      Current Medical research suggests that there are benefits of drinking copper water. Water stored in copper vessels has been proclaimed as health elixir by ancient Ayurveda as well.

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