What is a TDS Controller in a Water purifier?

Last Updated on 13 February, 2024 by Sourav Roy

TDS is the amount of dissolved inorganic and organic impurities in water. While it by itself isn’t exactly unhealthy, water containing high TDS usually includes other harmful substances like arsenic, mercury, lead and so on. TDS Controllers are some of the best means of lowering the TDS levels of the water. What is TDS Controller? Well, we’ll answer that question in this article and tell you how you can keep yourself healthy by adhering to certain rules about TDS in water.

What is a TDS Controller in a Water purifier


What is the TDS of water?

What is the TDS of water

Let’s talk a little more in-depth about TDS. TDS Controllers are incredibly useful, and you’ll realise how once you learn how potentially dangerous TDS water is. TDS refers to the amount of total dissolved solids a body of water contains.

Most of the time, these dissolved solids are some inorganic salts, mixed in with some organic compounds as well. They’re present in the water naturally, but human activities such as urban development and farming also contribute to the increase of TDS in water.

Some of the elements high TDS water contains are calcium, magnesium, chlorides, and organic matter like leaves, silt or plankton. However, the TDS in water also includes toxic components of heavy metal like cadmium, lead, nitrate and arsenic.


Is high TDS harmful?

As mentioned earlier, high TDS by itself isn’t always unhealthy. Certain elements in water with high TDS can either benefit you or are harmless. However, these high TDS levels sometimes also have high concentrations of toxic substances. For example, this kind of water can contain heavy metals like arsenic, chromium, cadmium and even lead. These elements can harm your health.

Despite all that, there are still certain areas that have healthy water even with high TDS levels. Such areas include locations where industrial wastes don’t get dumped into water or soil and areas with farms that don’t use synthetic pesticides or fertilisers. Even if the TDS count of underground water of these areas reaches as much as 1800 mg/litre, the water can still be safe for humans.

With a few exceptions, most of the times the increased TDS levels will only be from useful minerals and bicarbonates that our bodies can naturally handle. High TDS only becomes harmful with the presence of toxic chemicals in the source water and goes beyond the count of 1200 mg/litre.

Recommended Reading: Arsenic Poisoning in Water – Sources, Effects & Prevention


What is the acceptable TDS value in drinking water?

What is the acceptable TDS value in drinking water

The ideal TDS value of drinking water should be as much as, or less than 500 mg/litre, according to the EPA and Bureau of Indian Standards (BIS).

You must know the TDS of your source water. If it’s anything more than the ideal amount, then you might need to opt for a water purifier to ensure safe drinking water.

In fact, the best water purifiers usually come equipped to deal with high TDS levels. So, if you don’t want to take chances with your health, it might be in your best interest to get one of these.

You can usually guess the TDS level of your water by taking a small TDS taste of the source. Here’s a table about TDS levels to help you decide if you should consume the water or go for a water purifier.

TDS Level (mg/litre)Rating
Less than 300Excellent.
300 - 500Decent, drinkable.
500 - 900Somewhat decent, but not fit for direct consumption.
900 - 1200Poor, unfit for consumption.
Beyond 1200Unacceptable.

If you want accurate readings of the TDS in your drinking water, then there’s a better alternative to guessing with the taste. You could go for a TDS meter instead, which is more precise and lasts a few years. So, you can use it multiple times.

Additionally, if you are concerned about TDS for the sake of your health, you should also have an idea about the safe water drinking guidelines in India.

Recommended Reading: How to check TDS of water


What is Reverse Osmosis (RO) Purification?

What is Reverse Osmosis (RO) Purification

As the name suggests, the Reverse Osmosis method of purification works by flipping the process of osmosis.

Regular osmosis is the natural need for liquids to move from a low concentration area to a high concentration one when separated with a semi-permeable membrane.

Reverse osmosis works the opposite way, with the liquid transferring from a higher concentration area to a lower concentration one. This transfer isn’t natural, of course. It’s done through the use of force.

For instance, take a path for water movement and divide it by a semi-permeable membrane. One side of this path has water with salts and minerals, while the other has clean water or none of it. Once force is applied to the side with a higher concentration, purified water comes through. The presence of the semi-permeable membrane and the direction the pressure comes from makes this happen.

Indeed, that’s how RO water purifiers work. The best RO purifiers can make the best of this purification method, giving you clean, drinkable water with low TDS. All solids, be they dissolved, or undissolved are restricted from entering the pure side due to the high-quality membrane engineering.

Advantages of RO purification

  • Treats hard water easily and reduces TDS levels.
  • Removes toxic elements like lead, mercury, fluoride, chlorine and arsenic, which can lead to illnesses. Lead can even cause brain damage and anaemia.
  • The mechanism is effective, and easy to understand with evidence supporting the effectiveness.

Disadvantages of RO purification

  • It removes all the minerals in the water, including the ones that the human body benefits from.
  • Doesn’t kill all bacteria and viruses, as microorganisms can pass through the RO membrane. Be sure to get a RO purifier with a UV filter to get rid of these.
  • The purification process is slow and produces more wastewater than pure water.
  • Certain elements can damage and break the RO membrane, and there’s nothing in place to alert the user of the breakage.

As with most purification systems, this one has its own flaws. Most of these can be overlooked in favour of safe drinking water. However, water wastage is going to be the most significant problems you’ll face. Companies are working towards reducing the problem; in the meanwhile, you can use the RO Waste Water effectively.

Recommended Reading: RO Water Purifiers – Pros and Cons


Recommended TDS value in RO Water

Recommended TDS value in RO Water

You can use a TDS Controller to get just the right amount of TDS in your water. You shouldn’t get rid of it completely, as WHO advises water with a TDS of below 30 mg/litre should never be drunk. Also, another WHO study shows that water is the best in taste and safety when it has TDS under 300 mg/litre.

In conclusion, the ideal TDS of the output water should be anywhere from 50 to 300 mg/litre. If you can’t decide anything specific, it’s best if you go for the average and set the TDS Controller for about 150 mg/litre.

If your home’s source of water is contaminated with heavy metals, then it would likely be best to go for a TDS level of 90 mg/litre. The TDS controller is going to add minerals from the source water to produce the desired output. All the minerals present in the source water will come in small quantities.

To make it easier for you, our experts suggest a smaller range of 90 – 150 mg/litre, depending on the level of pollution in your area.

Recommended Reading: Safe Drinking Water Guidelines in India


What is TDS Controller?

What is TDS Controller

A TDS Controller is a screw-based bypass valve that controls the level of salt in the pure output water. It takes a small percentage of source water, which is also adjustable, into the output water. Afterwards, the mix of water goes through a UF or carbon filter, before going to a UV chamber if there is one.


Why do we need a TDS controller?

Why do we need a TDS controller


RO Water Purifiers can reduce the TDS of water by as much as 90%-95%. In other words, using this kind of water purifier with source water that has low TDS levels under 500 can produce water with extremely low TDS.

It can go under the minimum advised amount of 30 mg/litre, thus causing damage to the body. Your body is going to put in much more effort to make up for the lack of minerals. This is where TDS Controllers come in. With these, you can set the levels to be a little higher, but also keep the levels from rising to past a healthy amount.


How does a TDS Controller work?

How does a TDS Controller work

Now that we know what the TDS Controller is let’s take a look at how it works.

The TDS Controller is a valve that uses portions of the source water to adjust the TDS. Based on what the user sets, it restricts the TDS levels from going up past a certain amount, while ensuring that the purified water has a TDS amount of the set level.

It does so by taking little bits of the salt from the source side. For instance, if you set the controller to give you 150 mg/litre, then you’re going to get an amount close to that, without the TDS going past that amount.

Advantages of TDS controller

  • There are several advantages you can enjoy when you use a TDS Controller, including more control over your health.
  • As stated above, using an RO purifier with a TDS Controller allows you to adjust the amount of TDS you want in the output water. You can change the setting to another level without having to replace the water already in the filter. You can also prevent any of the source water from coming in, thus making the output water 100% RO purified.
  • Another great thing about these controllers is that your purified water tastes more natural, as the TDS Controller adds minerals from the source water, including the naturally present ones.
  • As the TDS Controller adds in parts of the source water with the purified output, that also means there is less water getting wasted in the purification process. This makes RO water purifiers fitted with these more environmentally friendly.

Recommended Reading: 9 Best Water Purifiers In India 2024



What is a TDS Controller? Now you know the answer to that question, and you also learn how to use it to get the best mix of taste and healthiness. You can always go for filters that have TDS Controllers built into them and are some of the best out there.

You also have the option to get a water purifier with a mineral cartridge in place, but if you buy the ones with a TDS Controller instead, you’ll have much more control over your water.

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