What is MTDS in water purifiers and how does it work?

In today’s date where the availability of good quality water is decreasing day by day, I think everyone must have a water purifier in their home.

And when you go to buy water purifiers then you might have come across the terms like TDS or MTDS controllers. I think most of you must have at least heard about TDS, but what exactly is MTDS? Let’s know in detail

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What is TDS in water purifiers?

The full form of TDS is Total Dissolved Solids which refers to the total dissolved salts present in the water. Here, Salt does not mean table salt that we use in cooking. We are saying salt refers to all the minerals that are present in drinking water.

TDS is a measurement that is used to know the mineral content present in the water. It is measured in parts per million (ppm) or milligrams per litre (mg/L)

The TDS level and value depend largely on the source of the water. If you measure the TDS of water coming from natural sources, will have a higher TDS level than others sources. It’s because natural water sources contain all types of elements including both beneficial and harmful.

What is the use of TDS in water purifiers?

As I said in the above paragraph, TDS is a measurement of minerals and other salts present in the water. And we use TDS in water purifiers as a measurement to determine the effectiveness of the purification process.

The main purpose of the water purifier is to remove harmful contaminants from water to make it safe for drinking.

Natural water sources, such as groundwater and surface water, contain many impurities like bacteria, viruses, chemicals, chlorine, and other heavy metals. So the level at which these are present in the water is measured by this unit called TDS.

And we use water purifiers to remove these excess impurities present in the drinking water. Water purifiers use many methods and pass the original water through different channels and filters to remove impurities, microorganisms, pathogens, unwanted elements and heavy metals from water.

Those channels are generally RO, carbon filters, UV and UFs. We have covered these points in more detail under the heading “How MTDS Works

But the point here is if a water purifier removes all minerals from water, then it will give us “dead” water to drink. It means water will be devoid of all the essential minerals that are needed for our body. And consuming water with low TDS levels can result in mineral deficiencies in our bodies.

Therefore, it is important to maintain a balance between both the process that is removing harmful impurities and preserving the essential minerals in our drinking water. The TDS level can be known as high or low just by knowing the taste of the water.

Water with high TDS levels will taste salty, bitter or metallic. On the other hand water with a low TDS level will make the water taste flat or tasteless.

As per WHO, water with a TDS level of less than 100 ppm is considered low. And water with a TDS level above 900 ppm is considered high.

In general, drinking water with a TDS level between 150-500 ppm (parts per million) is supposed to be ideal. But you can control the TDS level of your water based on your preferences and needs.

And this is where the use of the Manual TDS controller comes into the scene of water purifiers.

What is an MTDS controller in water purifiers?

A Manual TDS controller is a tool that allows the customer to adjust the TDS levels of the purified water to desired levels.

MTDS controller in water purifier

Water purifiers not only improve the taste of water but also add important minerals back into the water.

And today many RO purifiers come with a Manual TDS(MTDS) controller that can be used to add essential minerals like calcium and magnesium back into the purified water as per your need. This also helps to give a good balance of pH level in the water.

Some salts like calcium, magnesium, sodium and potassium are important and necessary for our body, while some salts like nitrate, chlorine and sulphate are not much useful and also make water taste bad and should be removed.

And RO (Reverse Osmosis) membrane is used to remove these dissolved salts from the water. But as I said, there must be some percentage of dissolved salt in our drinking water. And to control this percentage or level of salts we use a manual TDS controller or MTDS controller.

To know how an MTDS helps to maintain the mineral level in the water, you have to understand the working of the entire filtration process.

How MTDS works?

Nowadays, all water purifiers use multiple purification technologies for complete water purification.

In addition to widely used RO and activated carbon filters, today’s water purifiers are also equipped with UV and UF technologies to ensure that all impurities and microorganisms are removed from the water.

UV is commonly used as a pre-treatment for RO that removes harmful bacteria and viruses before being treated by the RO membrane.

Let’s understand the use of each of these parts so that you can later know what is the use of a manual TDS controller.

Activated Carbon Filter– There is an activated carbon filter attached inside the water purifiers to filter out many organic compounds, chlorine, arsenic, fluorides, pesticides, herbicides and other impurities.

Reverse Osmosis– All water purifiers use reverse osmosis (RO) systems to sweeten the taste of water by removing dissolved solids such as salt, heavy metals and minerals that affect the taste of the water.

UV Technology– UV technology uses ultraviolet rays to disinfect water by destroying the DNA of bacteria, viruses, and other microorganisms present in the water. This also eliminates harmful bacteria and viruses from water but does not remove dissolved solids or other impurities.

UF technology– UF means Ultra-Filteration. It makes the filtration process more effective by using a membrane with pore sizes of 0.01 to 0.1 microns. This membrane acts as a physical barrier for larger particles like bacteria, viruses, and other suspended solid particles. As a result, it only allows water molecules and small particles to pass through the membrane. UF also does not remove dissolved solids or chemicals.

In short, Activated carbon filters and RO membranes remove 90% of dissolved impurities and contaminants from water, whereas UV and UF are mainly used for disinfection purposes.

You have understood the basic working of a water purifier. Now let’s know how MTDS comes into play in this entire purification system.

MTDS is a small tool or valve that has 2 inlets: Water Input 1 and Water Input 2.

  • Water Input 1 receives the purified water output from the RO membrane.
  • Water Input 2 can receive water from a variety of sources depending on the specific water purifier model and manufacturer.
    • It can either receive raw water directly from the source or filtered water from an activated carbon filter or UF membrane.
    • This means that the second inlet receives water without passing through the RO system.
    • It bypasses the RO membrane so that the water retains its natural minerals and elements.
  • The outlet pipe then delivers a mixture of both the RO-filtered water and the water that bypasses the RO membrane.

And you can use this MTDS controller to control the level at which water can be bypassed. You can increase or decrease the TDS level of purified water by rotating the screw of MTDS. This allows you to customize the flavour of the water to your liking.

How to operate the MTDS?

To adjust the TDS level using the MTDS regulator, you need to first open the outer cover of the water purifier using a screwdriver. After opening the outer cover you need to locate the MTDS regulator. Once you have located the regulator, look for the screw that controls the TDS level.

You can use the screw to decrease or increase the TDS level in the water, by rotating the screw clockwise or anti-clockwise respectively.

Note: It is important to note that not all RO water purifiers have the MTDS feature and it is not always easy to adjust the TDS level yourself. So you call the customer care of the water purifier company for the first or second time, and they will send a technician for the same.

You can observe how they are doing it and controlling the screw to maintain the TDS level. And from the third time onwards you can do it yourself. You can also watch some videos to control the screw of MTDS.

Is MTDS 100% effective in maintaining the mineral level of water?

I think till now you must have understood the use of the MTDS controller. It is designed in such a way that it maintains the natural mineral content in water by controlling the level of minerals that are removed by the reverse osmosis (RO) membrane.

But if you think practically, since we allow the raw water to bypass the RO membrane, it actually allows many contaminants and heavy elements to go into the drinking water.

And if you are living in areas where the water source is highly contaminated with heavy metals, bacteria or viruses, the chances of passing on impurities increase when using MTDS.

In such cases, it is important to allow the source water to pass through all filtration systems such as RO, UV, and activated carbon filtration without bypassing the water. And that’s why many companies have introduced a part called Mineralizers

Alternative to MTDS: Mineraliser/Mineral Cartridges

Now many companies have started using water mineralizers or Mineral cartridges instead of MTDS controllers. It is because mineralizers use natural minerals to add minerals to the purified water, rather than relying on the manual adjustment of the MTDS controller.

So you can say that the mineralizers are considered a safer option because there is no such system in the mineralizers where water is bypassed through the RO membranes.

Mineralizer or Mineral cartridges

Mineralizers or mineral cartridges work by adding minerals to the purified water after the filtration process. In the above image, you can clearly see that the cartridges are made up of small beads or rocks that contain minerals like Carbon, calcium, magnesium, potassium, and PH stone.

So after the completion of the filtration process, the water is allowed to pass through the mineral cartridge, and the beads or rocks release these minerals into the water. thereby adding all the essential nutrients. You can also call this process remineralization.

Mineral cartridges are generally used in combination with RO water purifiers because RO removes a considerable amount of minerals and other substances from water. And these cartridges restore some of the lost minerals.

When to use the MTDS controller and Mineralizer

The MTDS controller is useful when

  • The TDS level of the input water is already low – If you pass the water with low TDS through a water purifier, then the RO will entirely remove the minerals. So you need an MTDS. Manual control will mix some amount of direct water to the RO water to maintain the desired TDS level
  • Input water does not contain heavy metals(arsenic, lead, etc) – In this case, you can use MTDS. Otherwise, it is better to go for water purifiers with Mineraliser.

The Mineralizer is useful when

  • The TDS level of the input water is high
  • Input water comes from the areas where the water source is contaminated with heavy metals, bacteria, or viruses

Difference between MTDS and Mineralizer

MineralizerMTDS Controller
Adds essential minerals to purified waterAdds or mix the raw water to the water that is passed through the Reverse Osmosis system
Contains a mineral cartridge Has a valve or screw mechanism
Adds a fixed amount of mineralsAdds almost all minerals
Cannot remove minerals from source waterCan control the ratio of bypassed and RO-filtered water and hence maintain the source water minerals
Comparatively expensive and needs replacement at regular intervals(5-6 months)Cost-effective and no need for replacement
Useful when the TDS level of the input water is highNot recommended for areas with highly contaminated water


So now you must have understood what is MTDS in water purifiers and how it is different from mineralizers. I also made a detailed comparison of Mineralizers and MTDS controllers.

Although they serve the same purpose of enhancing the taste and health benefits of drinking water, they differ in their working principles and the extent to which they can control the mineral content of water.

So next time you go to buy any water purifier, you can now ask the salesperson about these details and finalize which water purifier you need for your home. If you have any further doubts, you can comment below.

Frequently Asked Questions

What is TDS and MTDS in water purifier?

TDS or Total Dissolved Solids is the measurement of dissolved salts present in water. MTDS, or Manual TDS controller, is a feature where the water purifiers allow the consumer to adjust the TDS levels of the purified water to the desired levels of their needs

What is the meaning of MTDS?

The meaning of MTDS is Manual TDS controller. It’s a valve or screw type thing that can be controlled to adjust the TDS levels of the purified water to desired levels by bypassing the RO membrane.

What is RO UV Mtds water purifier?

An RO UV MTDS water purifier is a water purification system that uses a combination of Reverse Osmosis, Ultra Violet, and Manual TDS controller technologies to purify water.

How much TDS is good for drinking water?

As per WHO, water with TDS levels less than 100 can throw our body’s electrolyte balance off. Ideally, the TDS level for drinking water should be between 150-500 ppm (parts per million) for taste and health.

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About the author
As a current electrical engineering student, I have a strong interest in gadgets and an in-depth understanding of how they work. On my kitchen blog, I share my knowledge on a variety of electrical kitchen gadgets, offering reviews, repair tips, and buying guides. Whether you are looking to upgrade your kitchen appliances or simply want to learn more about the inner workings of your gadgets, I am here to provide valuable advice. In addition to my technical knowledge, I also share my experiences and tips on how to clean and maintain your kitchen gadgets.Connect with Us :LinkedIn | Instagram | Facebook

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