What are total dissolved salts(TDS) & How to reduce Them?

We all have learned in school that water is a universal solvent that is tasteless, colorless, and odorless and can pick impurities pretty easily.

So now, you might think that if water is tasteless, colorless, and odorless then why does drinking water taste or smell muddy, salty, or sometimes full of nasty odor.

According to experts, one reason we can taste water is because of the presence of dissolved impurities which are otherwise known as TDS or Total dissolved solids. It generally comprises inorganic salts (calcium, potassium, magnesium, sodium, chlorides, bicarbonates, and sulfates), salts, metals, organic matter, cations, or anions.

But where does TDS come from and what is TDS of drinking water?

Drinking water which we consume nowadays contains harmful chemicals which usually originate from natural sources, urban run-off, sewage, industrial wastewater, and chemicals used for the water treatment process and sometimes the nature of the piping or hardware used at homes.

If we look through the terms of technicalities, any impurities that have molecules greater than two-micron fall under this category. The filtration process removes contaminants which are about 0.45 microns and come from multiple sources.

If there is a high amount of TDS present in the drinking water, and you are consuming that without purifying then it can prove fatal and can also give rise to multiple health issues. Hence, it is important to take care of TDS especially when it comes to consuming them.

Many experts suggest measuring TDS before buying any water purifier! But why is measuring Total dissolved solids important?

The main reason why it is advised to measure TDS in water is to discern its overall quality. If the water has high TDS then it means the presence of chemicals & contaminants can be harmful to the health. Hence regular checking of the TDS level is vital. Here are some other reasons for checking Total dissolved solids:

1. Health Hazards: Some dissolved substances like copper, fluorides, arsenic, and lead at a high level can affect your health if consumed for a long period of time.

2. Plumbing and Appliances: Dissolved calcium and magnesium salts can form a scale or build-up in the pipes and even reduce the lifespan of your home appliances.

3. Cooking: TDS levels below 500 ppm generally are not considered harmful, although they can alter the taste of the food or beverage.

So does it mean water that has more than 500ppm TDS level is not safe for drinking? How many levels are there and what are the acceptability and unacceptability factors in water?

Water, which has more than 500mg/l is considered to have a high TDS level and it is recommended to be treated before consumption. Although low TDS can indicate better water quality, very low TDS levels in water can lead to a flat or even slightly bitter taste. Here is the chart to know what is the permissible range of TDS in drinking water.

TDS Levels in mg/liter

Acceptability/ non-acceptability factors

TDS less than 50

Dissolved solids this low indicates their lack of natural nutrients as well as minerals. So it is not considered acceptable.

TDS between 50-150

The presence of TDS in between this range is considered acceptable.

TDS between 150-250

The presence of TDS in between this range is the healthiest range.

TDS between 250-500

If the dissolved solids are in between this range, then there is nothing to worry about, it is acceptable for drinking.

TDS between 500-900

If in this range then your tap water must be purified.

TDS between 900-2000

If the TDS is in this range, then you need an RO water purifier to reduce the level.

TDS above 2000

It is better if you use drinking water from other sources, as it is not safe for consumption.

Is RO water purifier the only source on how we can reduce TDS?

Generally, we recommend using RO purifiers at home to treat my tap water for consumption and daily use. But to answer this question, no it is not the only source. RO is most commonly used in Indian households and it is pretty convenient. Let’s check out some other features:

Reverse Osmosis or RO – It is mostly used in water filters and it is a reverse process of osmosis that is carried out with the application of external energy. It has membranes that allow the water molecules to pass through and ensures that all the dissolved salts and contaminants are left behind. Reverse osmosis would require the filter to put in enough energy so that it can push the water out of the other side.

Distillation – Through this process, the contaminants are removed by evaporation. The water is boiled to the point it produces vapors which then rise to the cool surface and then condense back into liquid form. The dissolved salts which don’t vaporize settle at the bottom provide distilled water. This process can be time-consuming, inconvenient, and not always effective. Here are some types of Distillation:

a) Simple Distillation

b) Steam Distillation

c) Vacuum Distillation

Deionisation (DI) System – Here the total dissolved solids are removed through ion exchange. When the water passes through a membrane with positive & negative electrodes, positive ions detach themselves and move towards the negative electrode which results in de-ionizing the water.