TDS (Total Dissolved Solids) represents the total concentration of all the dissolved substances in water.
TDS in water comprises inorganic salts and a small amount of organic matter.
Common inorganic salts that can be found in water include calcium, magnesium, sodium, and potassium, which are all cations, carbonates, bicarbonates, chlorides, nitrates, and sulfates, which are all anions. Cations are positively charged ions and anions are negatively charged ions.
The most important thing to note here is that the impurities, like dust, dirt, mud, and rust, do not constitute Total Dissolved Solids. This is because these impurities remain suspended (or settle at the bottom) in water and do not dissolve.
Dissolved solids can easily pass through a filter with 2-micrometer (or smaller) pores. But the suspended/settleable solids can be easily filtered out with such a filter.
From Where Do these Dissolved Solids Come in Water?
TDS in water supplies can originate from both natural sources and as a result of human activities. Sewage, agricultural and urban run-off, and industrial wastewater are the most common sources of Total Dissolved Solids in water.
Rivers flowing through mountains contain water with high levels of dissolved solids because the water flows through rocks that have mineral deposits and high salt content.
The most common dissolved solids are calcium, magnesium, phosphates, nitrates, sodium, potassium, and chloride. Mostly found in groundwater and river water, these are naturally occurring and are harmless for the human body.
However, some constituents of TDS like pesticides, lead, arsenic, and fluoride can be very harmful to human health. These constituents enter water as a result of human activities like sewage, agricultural and urban run-off, and industrial wastewater.
Why Do you Need to Measure Total Dissolved Solids?
Because testing the level of TDS in your water is the easiest way to analyze the overall quality of your drinking water.
Although there is no proof of any negative health effect of high or low TDS levels, it is used as an indicator of the presence of a broad array of chemical contaminants.
The Bureau of Indian Standards (BIS) has set the acceptable limit of TDS in drinking water at 500 mg/L.
Drinking water, with TDS levels higher than 1000 mg/L, is generally considered unfit for human consumption. A high level of TDS is also a direct indicator of potential concerns and calls for a thorough analysis.
Mostly high levels of TDS in drinking water are a result of the high concentration of minerals like calcium and magnesium. These minerals have little or no short-term health effects. But harmful and toxic contaminants like lead, arsenic, cadmium, nitrate, and others, have a serious effect on your health.
If you are living near highly polluting industrial zones and agricultural regions with a long history of using chemical fertilizers and pesticides, then there is a very high probability of these toxic contaminants mixing with the water source.
In such a case, apart from testing the TDS level of the water, you should also get your water tested in a laboratory for finding the presence of any harmful or toxic contaminants.
In areas where the TDS content of the water supply is very high, the individual constituents should be identified and the local public health authorities consulted.
What Happens to the Water When TDS is High?
a) The high concentration of dissolved solids in water causes water filters to wear out sooner. If the water at your home has high levels of TDS then you will have to replace the filters and membranes more frequently as compared to homes that have low TDS water.
b) A high level of TDS in water makes the water taste bitter and salty. In a study conducted by the World Health Organization (WHO), the palatability (acceptable taste) of drinking water has been rated by panels of tasters in relation to its TDS level as follows:
c) Bathing with high TDS water makes your skin rough and dry. It also damages your hair making them rough and dry, causing dandruff and hair fall.
d) Calcium and magnesium, two minerals commonly found in TDS, can cause water hardness, scale formation, and staining. High levels of minerals in water lead to scaling on bath fittings, water pipes, water heaters, and household appliances.
e) The high TDS level makes water hard. Apart from drinking, hard water poses several other challenges like soaps and detergents do not produce as much lather.
Are you worried about the excessive dryness of skin and sudden hair fall or dandruff? Chances are it is because of the calcium and magnesium minerals that make your water hard. Changing your soap or shampoo is not the solution. The solution is quite simple, you need to use a hard water softener for your bathroom. Hard water softeners are small, affordable, and easily fit on any tap or showerhead. We have written a detailed post on how hard water softeners can bring back the softness and shine of your skin and hair. This post also covers the best water softeners reviewed by our experts.
Health Effects of High TDS in Drinking Water
It is a widely known fact that high levels of TDS in drinking water can give water a bitter or salty taste, but it is not harmful to your health. In fact, minerals like calcium and magnesium, which are often the reason behind high TDS levels, are actually beneficial to your health.
However, if the TDS level of your drinking is above 500 PPM then it is recommended that you get the water tested for harmful impurities like lead, arsenic, mercury, fluoride, etc.
A high TDS level is usually not a health hazard as long as the dissolved solids are essential minerals and not harmful heavy metals and chemicals.
No health-based guideline value is proposed for TDS. However, drinking-water guidelines are available for some of its constituents, including lead, arsenic, cadmium, fluoride, nitrate, etc.
If you suspect or if the laboratory tests point to the presence of lead, arsenic, mercury, fluoride or other harmful impurities then you should use a multi-stage RO water purifier.
You may want to look at the top RO water purifiers for purifying high TDS water.
Is Low TDS Water Harmful?
Water with an extremely low level of TDS is undesirable for most consumers because of its flat, dull taste.
Also, demineralized or very low TDS water is not suitable for athletes and people with highly active lifestyles. But for most people, drinking water with a low TDS value doesn’t pose any health concern.
Water is not the only source of essential minerals like calcium and magnesium. The food that you eat also contains these minerals. Your body’s mineral requirement can be easily fulfilled by the food that you eat.
Apart from the dull taste, water with excessively low TDS is more corrosive and can leach harmful metals such as lead or copper from plumbing pipes and hardware.
Drinking water with moderate amounts of TDS is the best. Water with moderate TDS tastes better than water with very low or very high TDS levels.
What are the Guidelines for TDS in Drinking Water in India?
World Health Organization (WHO) report on TDS in drinking water points out that reliable data on possible health effects associated with TDS in drinking water is not available.
No health-based guideline value is proposed for the ideal TDS of drinking water. Because TDS in water can be high because of many factors so, in areas where the TDS content of the water supply is very high, the individual constituents should be identified.
The Bureau of Indian Standards (BIS), the organization that defines the drinking water quality guidelines in India, has set the acceptable limit of TDS in drinking water at 500 mg/L. However, the guidelines also mention that in case no alternative source of drinking water is available, then this acceptable limit can be relaxed to 2,000 mg/L. The BIS report also mentions that if the TDS level of the drinking water is higher than 500 mg/L then this may result in a decrease in palatability (acceptable taste) and may cause gastrointestinal irritation.
How is TDS Measured?
There are two methods of measuring Total Dissolved Solids in water: gravimetric analysis and conductivity.
Gravimetric Method
The gravimetric method is the most accurate but it is time-consuming. In this method, the liquid solvent or water is evaporated and the weight of the remaining residue is measured to calculate the TDS level. This method is ideal in case of high TDS concentrations and if inorganic salts constitute the majority of TDS.
Electrical Conductivity
Electrical Conductivity is the most popular and also the easiest method to find out the TDS of drinking water. The electrical conductivity of water is directly related to the concentration of dissolved ionized solids in the water. TDS meters work on the same principle of conductivity. Although this method is not accurate as the gravimetric method, it is definitely the quickest and easiest way to find out an approximate value for the TDS level in the water.
You may like to check our detailed post on how to check the TDS level of water at home.
How to Reduce or Remove TDS in Water?
There are 3 major ways to reduce or remove TDS in water:
Reverse Osmosis (RO)
Reverse Osmosis or RO purification is the most popular water purification technology to get rid of excessive dissolved solids in the water. RO process removes virtually all dissolved impurities, including essential minerals and harmful heavy metals like lead and arsenic.
The process uses specially designed RO membranes with a pore size as small as 0.0001 microns. The small pore size only allows water molecules to pass through and filters out every other impurity. Most RO membranes reduce the TDS level by up to 90-99%.
Distillation
Distillation removes contaminants through the same process used in nature, evaporation. The process involves boiling water to produce steam or water vapor. As water is boiled, water evaporates in form of steam but the dissolved solids are unable to evaporate. The steam rises to a cool surface, and once the steam cools down it condenses back into the liquid form.
Deionization
The Deionization process removes total dissolved solids through ion exchange. The process uses specially manufactured ion-exchange resins to exchange water ions with charged ions or dissolved solids. Deionization produces highly pure water that is very similar to distilled water. The advantage of deionization over distillation is that the process is quicker and does not result in scale build-up.
For homes, Reverse Osmosis (RO) is the most often used technique for tackling the problem of high TDS in water.
Conclusion
Whether the TDS level is a cause of worry or not depends on the kind of minerals, metals, and chemicals that make up total dissolved solids in your water supply. Unfortunately, this is not as easy as finding the TDS level as it requires more advanced testing.
TDS is not the only indicator of how pure or contaminated your drinking water is. TDS is only one of several indicators of the purity of water. Water may contain a whole lot of contaminants like mud, dust, rust, sand, bacteria, viruses, cysts, and more.
The water purification technology you use depends on the source and quality of the water. For more details on how to find the best water purifier for your home, you should check the water purifier buying guide.