What is TDS in water? Why measure total dissolved solids?

Reverse Osmosis Water Filter

Many people do not understand what TDS is in water and what total dissolved solids are present. The total dissolved solids content index can directly reflect whether your water quality is safe. Next, in this article, you can learn why you need to measure total dissolved solids and how to reduce TDS in water.

What is TDS in water?

TDS refers to the total amount of all solid substances dissolved in water. These solid substances can include inorganic salts, organic substances, and other chemicals dissolved in water. The concentration of TDS is usually expressed in ppm. Measuring TDS in water can help assess the purity and suitability of water quality. High concentrations of TDS may affect water's taste, appearance, and suitability. Therefore, understanding and monitoring the TDS concentration in water is essential to ensure the safety of drinking water.

What are common total dissolved solids?

Common total dissolved solids (TDS) include the following types of substances: calcium, magnesium, sodium, potassium, chlorine, zinc, aluminum, copper, arsenic, iron, fluoride, herbicides, sulfates, bicarbonates, nitrates, phosphates, pesticides, industrial wastewater

Where does TDS come from?

The sources of TDS are mainly natural and anthropogenic. Natural sources include groundwater, surface water, and precipitation, while anthropogenic sources include industrial wastewater, agricultural discharge, urban sewage, etc. The level of TDS directly affects the taste of water, the drinking water's safety, and the water's suitability.

Are total dissolved solids in water good or bad?

Whether total dissolved solids in water are good or bad depends on its TDS content and the purpose of the water body.

Good aspects:

  • Provide essential minerals: The right amount of TDS contains minerals such as calcium, magnesium, potassium, etc. that are beneficial to the human body and can supplement the needs of the human body.
  • Improve taste: The right amount of minerals will make the water taste better and more "mineral water".
  • Promote health: Some minerals are beneficial to human health, for example, calcium is important for bone health, and magnesium helps relieve muscle cramps.

Bad aspects:

  • Affect taste: Too high TDS content will cause the water to taste bitter, astringent, salty, or even metallic, affecting the taste.
  • Affect water pipes and equipment: Excessive TDS content will cause scale deposition, affecting the service life of water pipes and electrical equipment.
  • Harm to health: Excessive TDS content may cause diseases such as diarrhea and kidney stones.
  • Affect agricultural production: Excessive TDS content will cause soil salinization and affect the growth of crops.

What is a good TDS reading for drinking water?

According to EPA secondary drinking water regulations, a good TDS reading for drinking water is recommended to be between 100 ppm and 500 ppm. TDS readings above the recommended range may affect the taste, appearance, and suitability of the water. However, water quality varies greatly from region to region, and tolerance for TDS varies. Therefore, any TDS reading above 1000ppm is unsafe.

What is a TDS meter?

A TDS meter, also known as a total dissolved solids meter, is an instrument used to measure the total dissolved solids content in water. Its principle is to use conductivity to measure the total dissolved solids in water, including dissolved inorganic and organic substances, such as salts, minerals, organic compounds, etc. TDS meters are mainly used in water treatment, environmental monitoring, food processing, and other fields.

Working principle of a TDS meter

The working principle of a TDS meter is to determine the dissolved solids content in water by measuring the conductivity of ions or molecules in water. When the amount of dissolved substances in water increases, the conductivity of water will also increase. The TDS meter calculates the content of dissolved solids by measuring the conductivity in water.

The working method of a TDS meter

Prepare the sample: Pour the water sample to be tested into a measuring container, usually a glass or plastic cup.

Calibrate the instrument: Place the TDS meter in a standard calibration solution, and adjust it according to the conductivity of the standard solution and the value displayed by the TDS meter.

Measuring samples: Insert the TDS meter into the water sample in the measuring container, wait for a while until the reading is stable, and read the value displayed by the TDS meter to get the total dissolved solids content in the sample.

Clean the instrument: Use pure water to clean the electrodes of the TDS meter to avoid cross-contamination.

Generally speaking, TDS water quality charts usually show the classification of water quality for different ranges of TDS concentration. The following is the general trend of a common TDS water quality chart:

TDS water quality chart

  • 0-50 mg/L: high-quality water quality, very pure.
  • 50-150 mg/L: good water quality, suitable for drinking.
  • 150-300 mg/L: fair water quality, still drinkable, but may have some slight taste.
  • 300-600 mg/L: average water quality, may have a noticeable taste or slight precipitation.
  • 600-900 mg/L: poor water quality, may have a noticeable taste and precipitation.
  • 900 mg/L and above poor water quality, not suitable for drinking.

Why measure total dissolved solids?

Measuring total dissolved solids is very important. By measuring the TDS of water, we can better understand the water quality, so that you can take appropriate measures to solve water quality problems and ensure the health of drinking water.

Evaluating water quality safety

TDS is one of the important indicators for evaluating water quality. The total dissolved solids content in water can be understood through parameters. High TDS content indicates that the water contains too many minerals and salts. Therefore, water with high TDS content is unsafe and it is recommended not to drink it.

Taste and smell

Water with too high total dissolved solids content may have a very unpleasant odor. So, how to improve the taste of water with too high total dissolved solids content? It is recommended to use the ITEHIL reverse osmosis water filtration system to improve it because ITEHIL uses PP cotton + activated carbon + reverse osmosis membrane filter element to remove odor in water.

Learn More: What is a reverse osmosis system

Health and Safety

Drinking high TDS water is unhealthy because high TDS water may contain heavy metals, such as lead, mercury, arsenic, etc., and heavy metals will directly affect health. Therefore, it is recommended to use a reverse osmosis water filtration system to filter heavy metals contained in water.

Cleaning and Maintenance

Generally speaking, water filtration systems can reduce the total dissolved solids content, but high TDS water can easily cause scaling inside the water filtration system, which may affect the life and performance of the equipment. Therefore, regular testing of TDS will help your water filtration system to work properly. At the same time, your water filtration system also needs regular cleaning and maintenance to make it easier to use the water filtration system next time.

What causes excessive TDS in drinking water?

Geology and soil composition

Groundwater usually flows through rock and soil layers with high salt content. These salts and minerals dissolve in the water, increasing the TDS content in the water. Especially in saline-alkali areas, groundwater is affected by saline-alkali soil and has a high TDS content.

Human pollution

Human activities such as industrial wastewater, agricultural discharge, fertilizer and pesticide residues, and household wastewater can cause harmful substances to enter the water body, increase the TDS content in the water, and affect the water quality.

Groundwater level changes

When the groundwater level drops, the groundwater is in contact with the soil and rock formations for a longer time, which makes it easier to dissolve more salts and minerals, resulting in higher TDS content.

Water treatment processes

Some water treatment processes, such as over-softening and reverse osmosis filtration, may strip minerals from the water, making the water rich in TDS.

Pipeline leaks and pollution

Corrosion, leaks, or pollution in old pipes may cause external harmful substances to enter the water and increase the TDS content.

Changes in the natural environment

Changes in the natural environment, such as climate change, changes in precipitation, and river siltation, may lead to changes in the TDS content in water bodies.

Earthquakes and natural disasters

Natural disasters such as earthquakes and floods may cause damage to the soil and rock formations in the water source, causing the dissolution of gravel, salts, and other substances in the water to increase the TDS content.

How to reduce TDS in water

Reverse Osmosis

Reverse osmosis is a membrane separation process in which the feed water is compressed along the membrane flow surface. Pure water passes through the membrane and is collected, while concentrated water, containing dissolved and undissolved substances that do not flow through the water tank membrane, is discharged into the sewer. Reverse osmosis membrane technology is a highly efficient water purification technology that can remove most dissolved solids.

Learn More: How Does Reverse Osmosis Water Filter Work?

Ion exchange

When passing through the ion exchange column, the cations in the water and the anions in the water are exchanged with the H+ ions of the cation resin and the OH- ions of the anion resin in the exchange column, thereby achieving the purpose of desalination. Using ion exchange technology, the ions in the water are exchanged, thereby reducing the TDS content.

Water distillation

Distillation is a water treatment method that uses the different boiling points of each component in a mixed liquid or liquid-solid system to evaporate the low-boiling component and then condense to separate the entire component. It is a unit operation process that combines the two unit operations of evaporation and condensation. Its advantage is that it does not require the use of solvents other than the system components, ensuring that no new impurities are introduced, thereby removing most of the dissolved solids.

Activated carbon adsorption

A water treatment method that uses the physical adsorption, chemical adsorption, oxidation, catalytic oxidation, and reduction properties of activated carbon to remove pollutants from water. Activated carbon can adsorb organic matter, chlorine, etc. in water, thereby reducing the TDS content.

The above is all about total dissolved solids or how to improve water quality. I hope it will be helpful to you!


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