What is TDS in Water & Why Should You Measure It?

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Drinking water with high TDS values is one of the main reasons for water-borne diseases. High TDS levels can also affect the taste of the water as well.

If you want the right water purifier, then you have to understand all about the TDS and information related to it. In this article, we have mentioned it clearly for your reference.

What is TDS in Water

What is TDS (Total Dissolved Salts)?

It provides insights on the total concentration of dissolved salts or substances present in the water. To say in simple terms, TDS comprises of inorganic salts and small amount of organic matter.

Some of the common inorganic salts often found in water are magnesium, carbonates, fluorides, calcium, potassium, nitrates and sodium. Presence of these salts in small amount in drinking water is necessary. However, water can also have contaminants like arsenic, mercury, lead and other heavy metals. Presence of these chemicals in drinking water can be dangerous to your health.

Important Note – Having TDS levels up to certain level is considered acceptable for human consumption.

Acceptable TDS Levels in Water


What is the acceptable TDS levels that is suitable for drinking – this is the most common question that comes to people minds. To help you with this, we have provided a list below that provides insights on TDS levels and acceptability.

Acceptable TDS Levels in Water

TDS levels (ppm)Acceptability
Less than 50No – as the water doesn’t have enough minerals for health growth
50 to 300Excellent for drinking – as it has adequate minerals and less contamination
300 to 500Good enough for drinking
500 to 900Fair enough but you have to reduce TDS levels using water purifier before drinking it
900 to 1200Poor. So, you need high quality water purifier for decreasing TDS levels within range
Above 1200Not suitable for human consumption

Why Is It Important to Remove Excess TDS in water?

As we already know, TDS is a combination of inorganic salts and organic matter. Some of these salts are important for our health. But some of them are not – like industrial waste, human waste, and other chemicals like lead, arsenic and mercury.

These harmful pollutants are can dangerous to your health. If the TDS levels are higher than 500ppm then it can have damaging effects on your overall health. So, it is important to remove excess TDS levels in the water before consuming it.

What is the Easiest Way to Measure TDS levels Using Digital TDS Meter?

It is the easiest method of measuring TDS levels in the water. Main advantage of using a digital thermometer is that you don’t have to put additional effort in taking the readings or performing the mathematical calculations. To use the digital TDS meter, we have provided the simple step by step procedure below for your reference.


  • First, you have to remove the protective cap over the digital meter and turn it on.
  • Take a water sample from your kitchen tap or any other faucet in your home.
  • Now, immerse the digital TDS meter into the water sample up to maximum level. Usually, it has to be at least 2 inches. It is generally available on the meter to indicate it.
  • If there are any air bubbles in the water, we recommend to stir meter gently for removing them.
  • Now, you have to wait for about 10 to 15 seconds so that the reading gets stabilized.
  • To take the reading, you have to press down the “HOLD” button for few seconds and remove it out from water.
  • Some digital TDS meters provide reading directly in ppm while others represent in X10 symbol. If your device provides X10 reading, then you have to multiply the reading by 10.
  • Once you have taken then reading, shake the meter properly to remove any excess water and place the protective cap back.

Important Precautions:

  • Digital TDS meters are not waterproof, so you should not dip the device beyond the recommended maximum immersion level.
  • Never expose the device to direct sunlight.

Different Ways of Reducing TDS Levels in Water

Below we have mentioned three purification technologies which are helpful in removing high levels of TDS in tap or drinking water.

Different Ways of Reducing TDS Levels in Water

1. RO System (Reverse Osmosis)

RO water purification technology is the most efficient filter for removing contaminants. In this system, water is forced through a semi-permeable membrane which will remove the total dissolved salts. Usually, these water purifiers also come with carbon and sediment filter for removing physical contaminants like sand, dust and others. For best RO water purifiers, click here.

2. Water Distiller

For removing the impurities, this process uses the same process similar to nature – which is evaporation. During the process, only water can evaporate and contaminants cannot. This is the reason why rain water is pure in quality. As the contaminants are left behind, the water will be distilled and safe to drink. The distillation process includes water boiling to certain temperature for generating the vapor which will rise to a cooler surface for condensing back to liquid.

3. Deionization System (DI)

This process eliminates total dissolved solids through ion exchange by using resins that control the electric charge of ions. In this process, water ions are replaced with charged ions from the total dissolved impurities. Water filtered through this process is highly pure which is why DI cartridges are considered as high purity filters.

Why Should We Measure TDS in Water?

Analyzing TDS levels is the perfect way to know the overall quality of water. Some of the reasons you need for measuring the TDS levels are…

  • If the TDS levels are high, then it can affect the taste of water. The taste can be salty, bitter, or sulphuric based on the type of dissolved salt.
  • Water with high TDS levels are not recommend for drinking as they contain harmful impurities like arsenic, copper and lead.
  • Water purification system is the effective solution to remove TDS levels. However, if you want to know your water purifier is working properly or not, testing for TDS regularly is beneficial.
  • Though it is not harmful, cooking with water that has elevated levels of TDS levels (1000 ppm) can change the food taste.
  • If you are observing water spots on utensils no matter how well you clean them or if your clothes are fading quickly or if your tub, faucet and sink have build-up, then you have to test the water for TDS levels.
  • Water with high TDS levels usually contain high levels of calcium and magnesium. Hard water is collected in the pipes can form scale and build-up. This can result in costly replacements and decrease the life of your appliances.

What is TDS Controller or Modulator?

What is TDS Controller or Modulator

It is a screw-based device which controls the amount of total dissolved salts in the output water. Usually, RO water purifier removes 90% of TDS levels in water. Along with bad impurities, it will also eliminate essential minerals like magnesium and calcium as well. The presence of TDS controller will help to retain enough important minerals in the purified output water.

How Exactly Does a TDS Controller Work?

In this process, the input water will be divided into two parts. The first part flows through the RO membrane and undergoes purification. Instead of RO membrane, the second part will undergo UF membrane or UV chamber.

The output water from the purifier will be a combination of 1 part RO purified water and 1 part of UF purified water. This combination is actually controlled through a valve connected to the second part output. So, the TDS levels are controlled.

A TDS controller will adjust the TDS levels of output water according to the requirements of your choice. For example, you can set it to 150 mg/litre and change it to another level whenever you want without changing the water purifier. Apart from that, you can also close the second part completely if you want 100% RO purifier water.

Main disadvantage of TDS controller is that – only RO purified water will not be very pure. Because the TDS controller will mix some part of non-RO purified water to make sure the output water has enough minerals and chemicals that are originally available in the input water. However, this is a very small amount of water.

This may not be a major problem unless source water has polluted heavily with metals like nitrate, arsenic, lead and cadmium. If the output water has heavy metals under safe limit ratio, then it is definitely safe to consume it.

Difference Between TDS Controller and Mineralizer

Some RO purifiers come with alkaline mineral cartridge. These devices add minerals into the purifier water. They contain different layers of several materials that include mineral balls, pelletized activated carbon, antibacterial balls, tourmaline balls, PH booster ball, ceramic balls and others.

How Exactly Does Alkaline Mineral Cartridge Works?

Once the water has gone through the RO membrane, it will pass through the mineral cartridge. Here, the water will extract minerals from the several minerals layers present in the cartridge. Some of the mineral cartridges also come with PH booster balls which is responsible for improving the pH balance of the water and make it alkaline.

Alkaline Mineral Cartridge Works

Quality of mineral cartridge shows insights on variety of minerals present in it and that are added to the purified water. Some mineral cartridges also come with additional benefits like energizing water and others. This will help selective infusion of certain minerals.

This process is not possible with TDS controller. With TDS controller, the purified water will be combined some non-purified water at minimum concentration. To say in simple terms, the purified water will be infused with same minerals that RO eliminated but just in small amount. However, the water will be purified using UV or UF membrane. But heavy metals like lead, mercury or arsenic are not removed from the water. In theory, the RO purified water will be contaminated with normal water.

But the mineralizer is different as it will infuse minerals that are lost with RO purification process. But that doesn’t inc lude heavy metals.

This doesn’t mean TDS controller is ineffective. Both mineralizer and TDS have same importance when it comes to water purification technology. One of the main drawbacks of alkaline mineral cartridge is that it has no control over the TDS levels of output water.

For instance, if the input water has TDS of 200mg/litre, then output water will have 10 to 20mg/litre after undergoing RO membrane. Once it passes through the mineralizer, it will have 40 to 100 based on the mineral cartridge quality.

If the mineral cartridge is not good, then TDS output water will be just 30 to 40mg/liter which is actually unacceptable. In such case, you may not be able to adjust the TDS according to your choice.

Some Frequently Asked Questions

1. What are the health effects of high TDS levels in drinking water?

High levels of TDS can affect the water taste. And apart from that, it can affect the health of you and your appliance as well. But certain minerals that elevate the TDS like calcium and magnesium are helpful for health. TDS levels above 500ppm need to be checked for heavy metals and toxic particles. If the TDS levels are higher than 1000ppm, then it is unsafe for human consumption.

2. Is low TDS water harmful or helpful?

Water with 0 TDS is not harmful for your health. Water with low TDS is perfectly safe and high quality water. However, it may have flat taste. Rainwater actually has less TDS because of less evaporation. TDS levels between 300 to 500 are considered best for drinking water.

3. How Does Solids Dissolve in the Water?

These minerals can be from any source (natural and human activities). Usually, mineral springs have water with high TDS as the water flows through rocks that contain high salt content. Water source from Prairie provinces also has high TDS levels due to calcium and magnesium present in the ground.

Water can also get contaminated with human activities, agriculture, urban runoff, industrial waste water, wastewater discharges and salt.

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