What is TDS Controller/Modulator and Mineralizer? Which One to Choose?

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If you are planning to buy a new RO water purifier and have done some research online or offline then you must have come across some RO purifiers that come with an extra feature called ‘TDS Controller’.

It is also interesting to note that this same feature is sometimes marketed as ‘TDS Modulator’ by some water purifier brands. However, TDS Controller and TDS Modulator is one and the same thing and there is no functional difference between the two.

What the heck is this TDS Controller/Modulator?

The following text will answer all your questions about TDS controller in an easy and user-friendly manner.

Let’s begin then…

What is a TDS Controller?

In simple terms, a TDS Controller is a device that controls the TDS of water. Unlike the filters, cartridges, and membrane(s), TDS Controller does not filter or purify the water in any way.

Water TDS Controller

The image above shows a typical TDS controller, as you can see this is a small device. This is quite inexpensive and costs roughly around Rs. 50 only.

How TDS Controller Works?

TDS Controller is basically a manual device which consists of two water inputs, one water output, and a TDS Control screw.

Kent Grand Plus Purification Process

Water Input 1: Purified water output from the RO membrane

Water Input 2:
a) Purified Water from Activated Carbon Filter in case of RO+UV+TDS Controller Water Purifiers

OR

b) Purified Water from UF Membrane in case of RO+UF+UV+TDS Controller or RO+UF+TDS Controller Water Purifiers

Water Output: Mix of two water inputs in the required ratio.

TDS Control Screw: TDS Control screw controls the TDS value in output water by manually adjusting the flow of water from the two water inputs.

I) If TDS needs to be reduced then the flow of input water from the RO membrane is increased and the flow of input water from Activated Carbon Filter or UF membrane is reduced.

II) If TDS needs to be increased then the flow of input water from the RO membrane is reduced and the flow of input water from Activated Carbon Filter or UF membrane is increased.

Simply, Turn the screw clockwise to reduce the TDS level or anti-clockwise to increase the TDS level.

Please note, in most RO purifiers, TDS Controller is located inside the assembly along with all other RO parts. So for adjusting the TDS level you will have to first open the outer cover.

However, if you are not comfortable doing this, we recommend getting this done from a trained professional.

Recommended TDS Level in Drinking Water?

You should adjust the TDS controller such that the TDS level of purified water is between 50 to 150 ppm.

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Need and Benefits of TDS Controller?

Natural water contains several essential minerals like Calcium, Magnesium and may also contain harmful impurities like heavy metals, fluorides, and arsenic.

These minerals and heavy metals are what constitute ‘Dissolved Solids’ in water. The level or the presence of these Dissolved Solids in water is commonly referred to as TDS (Total Dissolved Solids) level of water.

The presence of minerals like calcium and magnesium in small quantities is what makes the drinking water healthy and it is very essential that the drinking water contains these minerals.

RO Membranes usually removes around 90% of dissolved solids from the input water, and that includes essential minerals.

What this essentially means is, if the input water does not have high TDS then chances are the RO Membranes will reduce the level of essential minerals to the significantly low level making the water unhealthy and not fit for drinking.

This is where the role of TDS Controller comes into effect. As detailed above, in such a scenario when the TDS level of input water is not so high, TDS Controller can be used to increase the TDS of purified water to a healthy level.

TDS Controller is basically used to increase the level of essential minerals in the purified water.

TDS Controller: Can it be Harmful?

In our opinion, TDS Controller is not an ideal way to add essential minerals in the purified water. In RO purifiers with TDS controller, 100% of the input water does not pass through the RO membrane.

Mixing RO purified water with non-RO purified water may result in presence of several harmful heavy metals like lead and arsenic in the purified water, as these impurities can only be removed by an RO membrane.

Should you Buy an RO with TDS Controller?

Keeping all the above discussion in mind, you should only consider buying an RO purifier with TDS Controller if:

• The TDS Level of input/raw water is low (lower than 900 ppm).
• Water does not contain heavy metals like lead and arsenic.

If the TDS level of raw/input water is high (higher than 900 ppm) or if the water contains harmful heavy metals then you should not choose an RO purifier with TDS Controller.

The above recommendation is given on the basis if the RO membrane reduces the TDS level by 90%. The lower and higher TDS level limits will change if the RO membrane reduces the TDS level more or less than 90%.

Be sure to check the specifications of the RO membrane before deciding to buy an RO purifier with TDS Controller or without TDS Controller.

Which Water Purifier with TDS Controller to Choose?

Now, if you have zeroed in on buying an RO purifier with TDS Controller then the following table will help you in finding the perfect match for your home.

TDS LEVEL IS WATER MUDDY? PRESENCE OF BIOLOGICAL IMPURITIES? IDEAL CHOICE
300 – 900 ppm No No RO+TDS Controller/Mineralizer
300 – 900 ppm No Yes RO+UV+TDS Controller/Mineralizer
300 – 900 ppm Yes No RO+UF+TDS Controller/Mineralizer or RO+UV+UF+TDS Controller/Mineralizer
300 – 900 ppm Yes Yes RO+UV+UF+TDS Controller/Mineralizer
Over 900 ppm No No RO
Over 900 ppm No Yes RO+UV
Over 900 ppm Yes No RO+UF or RO+UV+UF
Over 900 ppm Yes Yes RO+UV+UF

Is there any Better Alternative to TDS Controller?

There are now better technologies available to add back the essential minerals removed by the RO purification.

RO purifiers with Mineralizer cartridge are a much better option as compared to RO purifiers with TDS Controllers. Because in RO purifiers with Mineralizer feature, 100% of water passes through the RO membrane. This removes any possible chances of harmful dissolved solids and heavy metals accidentally entering your drinking water.

Next section talks about Mineralizer, the difference between TDS Controller and Mineralizer and which one is better.

What is Mineralizer or Mineral Cartridge?

RO Membrane does not differentiate between the good particles and the bad particles or the impurities. And this is one of the disadvantages of using an RO purifier.

RO also removes the essential minerals like calcium and magnesium from the water, so we need some way to add back the minerals removed during RO purification.

One way of doing that is by using a TDS Controller/Modulator, we have already discussed this in detail above.

Another, slightly more effective, way to add essential minerals is ‘Mineralizer or Mineral Cartridge’.

Mineralizer or Mineral Cartridge adds back essential minerals like Magnesium and Calcium in the proper concentration and helps in maintaining proper PH and Acid-alkaline balance in the water.

Below is an image of a typical mineral cartridge:

Mineral Cartridge

As you can see in the image above, the mineralizer (AKA Mineral Cartridge) consists of several types of particles. Water passes from one end to the other and several essential minerals are added, and acidic nature of water is reduced by balancing the PH value.

Difference Between TDS Controller and Mineralizer?

TDS Controller Mineralizer/Mineral Cartridge
100% of the input water is not passed through RO Membrane. 100% of the input water is purified by RO Membrane.
Not ideal for water containing harmful heavy metals like lead and arsenic. Since 100% water passes through RO purification, heavy metals like lead and arsenic are removed.
TDS Level of purified water can be increased or decreased. No option to adjust the TDS level of purified water.
Small and costs very less. Size is same as regular filters and cartridge used in RO purifiers, costs over Rs. 500.

Mineralizer or TDS Controller, Which One is Better?

Both Mineralizer and TDS Controller features are quite good and provide excellent benefits if used appropriately.

If the water supply contains industrial impurities like lead and arsenic then you should avoid buying an RO purifier with TDS Controller. Apart from that, RO purifiers with TDS Controller work well in most scenarios.

RO purifiers with Mineralizer feature can be used for water infected with lead and arsenic but these purifiers have no option to adjust the TDS level as per your requirement.

So, the answer to the question ‘Whether to choose an RO purifier with TDS Controller or Mineralizer’ would actually depend on the factors like presence of industrial impurities and your choice.

However, we feel RO purifiers with mineralizer feature have a little upper hand as compared to the RO purifiers with TDS Controller feature.

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