Total Dissolved Solids (TDS): Problems and Solutions


The measure of Total Dissolved Solids, also known as TDS, is a measurement of the combined total of the inorganic and organic substances dissolved in a given water source. Read on to learn more about TDS, and how its measurement can help you better understand your water quality.

What are Total Dissolved Solids?

TDS in drinking water are composed primarily of minerals, salts, and organic matter. TDS levels can be an indicator of overall water quality. However, it is important to remember that TDS is not itself a water contaminant; only a measurement of the amount of dissolved material in water.

Common inorganic salts that can be found in water include: calcium, magnesium, potassium, sodium, carbonates, nitrates, bicarbonates, chlorides and sulfates.

TDS are a leading cause of turbidity and sediment in water, and if left unfiltered may lead to other contamination.

Where do TDS come from?

TDS in drinking water are a product of both the natural environment and human activities. Environmental sources include salt deposits, mineral springs, and carbonate deposits. Non-environmental factors include agricultural and urban run-off, water treatment chemicals, and industrial and wastewater discharges.

Note: TDS is a measure of substances in a given water sample and is not a contaminant on its own.

Why measure TDS levels?

A TDS test can be used to determine the general quality of the water. A high TDS level is an indicator of potential concerns. More specific water tests are available that will provide a more comprehensive summary of what specific contaminants may be found in a 

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What are the risks of high TDS?

A high TDS measure alone is not a health hazard. The Environmental Protection Agency (EPA) considers TDS a secondary standard, or voluntary guideline, not a legal standard such as those set for contaminants considered harmful. The risks of TDS are mainly considered to be aesthetic, or an issue of color, taste, and smell. High concentrations of TDS can also have technical effects, leaving scale deposits, staining household fixtures, and corroding plumbing.

A high concentration of TDS may also indicate the presence of harmful contaminants, such as iron, manganese, sulfate, bromide, and arsenic, especially if TDS are the result of pollution.

What is the acceptable TDS level in drinking water?

TDS is measured in milligrams per unit volume of water (mg/L), or as a ratio of parts per million, or ""ppm"". For drinking water, the maximum concentration level set by EPA is 500 mg/L. TDS levels exceeding 1000 mg/L are considered unfit for human consumption.

While high TDS levels are of concern, a very low concentration of TDS results in flat tasting water. This is due to a lower mineral content, which many consumers consider undesirable.

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