What is TDS Controller and Mineralizer? Which is best for you?

If you are planning to purchase an RO water purifier for your home, then you must have heard about TDS controller and Mineralizer. Almost all the RO water purifiers come with either a TDS controller or a Mineralizer. Read on to know about these and whether you should buy an RO water purifier with a TDS controller/Mineralizer or not.

What is TDS Controller

A TDS (Total dissolved solids) controller is a device in RO water purifiers that regulates level of TDS in water.

TDS controller device

As you can see, this is a simple device with a controller screw on the top and input and output openings for water to pass through.

Why is TDS Controller necessary?

RO water purification is a powerful filtration process. It reduces the TDS of the water by as much as 90%. This means, that for an input of TDS 600, the output will be around 54. This level of TDS is not good for your body because it lacks in essential nutrients. Also, low level of TDS makes the taste of water unnatural or even bitter which can be hard to drink.

How does a TDS Controller work?

A TDS controller works by allowing mixing of small amount of impure water with RO purified water. This regulates the TDS based on the level set by you.

RO purification with TDS Controller

As you can see in the image above, before water is sent to RO membrane, some part of it is diverted and instead fed into another filter or membrane (It can be UF or MF or Activated Carbon or a combination of these).

Thus, a TDS controller has two input points.

Input 1: Highly purified water from RO membrane.

Input 2: Less purified water purified from other type of filtration such as UF/MF/Activated Carbon.

So, full output of TDS controller is a mixture of water from input 1 + small portion of input 2. This mixture is controlled with the help of a valve connected to the input 2 assembly, this is how TDS is controlled.

It’s obvious that a TDS controller is always used along with other types of filtration technologies because water added to control the TDS is raw and needs some level of purification before it is mixed with RO purified water.

This is how TDS controller removes one of the biggest drawbacks of RO water purification.

TDS Control Screw: TDS is usually controlled manually with the help of a control screw located inside the water purifier.

TDS control screw is connected to input 2. It means it will control the level of less pure water. Thus, if you want to decease the TDS, you should rotate it clockwise to decrease the flow of less pure water. Similarly, you can rotate it anticlockwise to increase the flow of impure water. This will increase the overall TDS of water.

Safe level of TDS in water is less than 300 – 500.

MTDS vs Taste Adjuster/Enhancer vs TDS Controller – What is the difference?

Once you start looking for RO water purifier for you home, you will come across different types of terminologies related to TDS controller.

MTDS is also called manual TDS. It means that you will have to control TDS levels with the help of TDS control screw. It is similar to regular TDS controllers. So, if you come across a water purifier with mTDS instead of a TDS controller, it is mostly a naming convention adopted by the brand.

Some water purifier brands also come with a taste adjuster, where you can adjust the taste of your water ‘depending on the source’. Again, this is also a TDS controller. Since amount of TDS is responsible for the taste of water, modifying the TDS levels will change the taste of water. For example, If your water comes from borewell, then it is likely that it is hard water with higher TDS. Reducing the TDS will improve or enhance the taste of water.

In short, all these terminologies are used to refer a TDS controller.

Advantages of TDS Controller

  • TDS Controller is quite cheap, costing less than 200 rupees.
  • It adds natural minerals essential for a healthy body.
  • It is environment friendly since water purifiers with TDS controller waster lesser water.
  • It makes water palatable by adjusting the taste of water.

Disadvantages of TDS Controller

  • TDS Controller is usually located inside the water purifier assembly. It means that you will have to open the water purifier covering when you have to reach out to TDS controller screw. This can be inconvenient. Thus, you should get this fixed with the help of the service technician during the time of installation.
  • One of the biggest limitation of a TDS controller is that if the source water contains heavy metals, then it is not a good option. This is because heavy metals such as cadmium, mercury, arsenic, nitrates, flourides etc. are harmful even in small quantities. And the small amount of impure water that is mixed with the RO water will contain heavy metals since they cannot be removed by other filtration methods such as UF/MF/Carbon.

To remove this drawback, you can use a Mineralizer instead of a TDS Controller.

Mineralizer / Mineral Cartridge

A Mineralizer is a mineral cartridge that contains essential minerals (such as magnesium and calcium) that are necessary for human body.


Mineralizer can be a good choice if your source water contains heavy metals such as lead, arsenic etc. because unlike a TDS controller it will add essential nutrients from cartridge present inside the water purifier.

How does a Mineralizer work?

Mineralizer is usually placed after the RO membrane. So that once the water is purified with RO, it can be enriched with minerals. Mineralizer basically works by extracting mineral balls from inside the cartridge and then passing these minerals onto the water. Some cartridges also come with pH booster balls to improve the alkalinity of water, while some claim to come with ‘energising’ benefits.

Advantages of Mineralizer

  • Biggest advantage of a mineralizer is that it is a good replacement for a TDS controller when your source water contains heavy metals.
  • It adds essential minerals into the water.

Disadvantages of Mineralizer

  • You cannot control TDS of water unlike TDS controller
  • It is more costly as compared to a TDS Controller

Difference Between TDS Controller and Mineralizer?

Should not be used with water containing heavy metals.Ideal for water containing toxic elements.
TDS Level of purified water can be regulated.Cannot adjust the TDS level of water.
Inexpensive – can come in less that 200 rupees.More costly – price starts from 500 – 600 rupees.
Prevents some amount of water wastage.Does not prevent any water wastage.

How to choose a water purifier with TDS controller / Mineralizer?

TDS LevelMuddy WaterPresence of GermsIdeal Water Purifier
Less than 300 – 500 PPMNoYesUV
Less than 300 – 500 PPMYesYesUV+UF
Less than 300 – 500 PPMNoNoCandle-based
Less than 300 – 500 PPMYesNoUF
Above 300 – 500 PPMNoNoRO+TDS Controller / Mineralizer
Above 300 – 500 PPMYesYesRO+UV+UF+TDS Controller / Mineralizer
Above 300 – 500 PPMNoYesRO+UV+TDS
Controller / Mineralizer
Above 300 – 500 PPMYesNoRO+UF or
RO+UV+UF TDS Controller / Mineralizer

As you can see in the above table, you should go with RO water purifier when TDS levels is more than 300-500 ppm. Whether you want to use a Mineralizer or a TDS controller will depend on factors such as presence of heavy metals in the water and whether you want to regulate TDS of water or not, pricing and so on.


TDS controller is the best method when it comes to maintaining healthy TDS levels. Hence, you should strongly avoid purchasing RO water purifier without TDS controller. However, in case your water has high level of toxic heavy metals, TDS controller becomes useless because even low levels of heavy metals can be harmful. Hence in such cases you should go for mineralizer-based water purifiers. Also, if the TDS of water is less than 500, then there is no need to buy an RO water purifier. Hence, in such cases, a TDS controller is not needed.

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