Acceptable TDS Level of Drinking Water – Is It 50, 150, 350 or 500?
The chemical formula for water is H2O. This entails that in each water molecule you find two atoms of Hydrogen and one atom of Oxygen. It is the purest form of water that conforms to this formula. In reality, drinking water has a lot of TDS in it. Let us look at what is the acceptable TDS level of drinking water during the course of this article. We shall look at the concept of TDS level in water in detail.
TDS – The Concept
In very simple terms, TDS refers to ‘Total Dissolved Solids’. These salts can be inorganic as well as organic salts. The principal constituents that comprise TDS are calcium, magnesium, potassium, sodium, bicarbonate, sulphates, chlorides, and nitrate ions.
Does the list look long and scary? In fact, it is not because you need a majority of these salts for ensuring good health. The proportion of these salts in drinking water is the matter of contention. We shall look at what is acceptable and what is not as we go deep into the article.
TDS – Source
The sources of TDS are various. They range from natural sources to agricultural and urban runoff. Industrial wastes and sewage are also sources of TDS in water. There are external factors like contamination from road paving materials, plumbing materials, and so on. Research shows that natural sources account for as low as 30 mg/litre or sometimes as high as 6000 mg/litre depending on the solubility factor of minerals found in different geographical regions.
TDS – Effects
Does TDS in water constitute a health hazard? This is a relative question because you need TDS within certain acceptable limits. It becomes harmful only when it exceeds these limits. In fact, the TDS concentration is more of an aesthetic hazard as compared to a health hazard because it is a secondary drinking water standard.
What can TDS do?
High concentration of TDS can cause water to become corrosive, salty or develop a brackish taste. This results in formation of scales in pipes, appliances like water heaters and washing machines thereby reducing their efficiency.
TDS – Acceptability Levels
The following tables explains the acceptability of TDS in drinking water. We shall look at the broad palatability levels of water before delving deep into the matter.
|TDS Levels in mg/litre||Palatability Quotient|
|Less than 300||This is considered excellent to drink|
|300 to 500||These levels are good|
|600 to 900||Fair|
|900-1200||This range constitutes poor palatability|
|Above 1200||This is an unacceptable range|
The above table conveys the palatability quotient of drinking water at different TDS levels. There is a difference between palatability quotient and acceptable levels of TDS. This table should make things clear. We go into the details explaining why water in the particular range is not acceptable.
According to the Bureau of Indian Standards (BIS), the upper level of TDS levels in water is 500 mg/litre (500 parts per million)
|TDS level in mg/litre||Reasons for acceptability / non-acceptance|
|Less than 50||This is a totally unacceptable level because water with such a low proportion of TDS does not contain the requisite minerals.|
|50-150||This is an acceptable level, especially when you consider water pollution through industrial wastes and sewage.|
|150-250||As far as cardiovascular health is concerned, this level of TDS is the healthiest.|
|250-350||This level of TDS is also an acceptable figure. You have many places in India having this level of TDS.|
|350-500||Any figure below 500 mg/litre is acceptable for drinking|
|500-900||TDS in this range is generally not acceptable for drinking. However, you can use RO water purifiers to reduce TDS levels below 500|
|900-1200||One should use RO water purifiers and try to reduce TDS levels to acceptable levels.|
|1200-1500||Using RO water purifier with TDS controller is the only option.|
|Above 2000||Unfit for drinking. Domestic water purifiers cannot handle this level of TDS in water.|
Certain Questions on TDS
1. Why TDS levels below 50 mg/litre is not acceptable for consumption?
This is a good question. When you have less TDS in water, it implies that water is pure with less quantity of dissolved salts. Under such circumstances, water should be pure. Therefore, the question is a valid one.
Remember, we had said earlier that TDS concentration is a secondary drinking water standard. Water having TDS levels of 50 mg/litre or less does not contain adequate minerals necessary for nourishing the body. Thus, this water is bland in taste. Secondly, very pure water has a high dissolution capacity. They can even dissolve plastic in small quantities. Therefore, it presents a health hazard, even though water is pure in every other respect.
2. What is the relationship between TDS in water and hardness of water?
Hardness is a measure of calcium and magnesium salts in water whereas TDS is a measure of total dissolved solids. It can be organic and inorganic solids.
3. How do you remove TDS from water?
Reverse Osmosis is one procedure for reducing TDS levels in water. You have a variety of water purifiers available in the market that can do this process for you. They do not eliminate TDS completely, but ensure that the output is acceptable for consumption. There is a flip side to this argument. Reverse osmosis can also remove essential calcium and magnesium salts; however, the latest water purifiers come with technology which does not eliminate these essential minerals while purifying drinking water.
TDS in Water Good or Bad?
We have seen various aspects of TDS in water. The acceptability levels and palatability quotient have their importance. However, the basic question remains, Is TDS in water good or bad?
To put in very simple terms, Zero TDS is not good for health. Similarly, higher levels of TDS are extremely harmful. You need to maintain the perfect balance. You cannot expect the common individual to carry the TDS meter in hand at all times to check the TDS levels. The best way is to trust out human instincts.
You can taste the water. If it is salty or unpleasant, you conclude that TDS levels are high. If the water appears tasteless or bland like you have in distilled water, the TDS levels are low.
TDS – A Brief Recap
- TDS comprises of organic and inorganic salts.
- Source of TDS is natural and manmade.
- Water with TDS up to 500 mg/litre is acceptable for drinking.
- TDS levels below 100 mg/litre do not contain requisite minerals.
Whether we like it or not, TDS in water is inevitable. You have the acceptability levels to adhere to. Refer to these tables and learn to live with TDS is water. TDS is not as bad as many people think it to be.