The Meaning of Total Dissolved Solids (TDS) in water

Understanding total dissolved solids (TDS) is an important step in evaluating your drinking water. Total Dissolved Solids (TDS) refers to the combined amount of dissolved minerals, salts, metals, and organic substances present in water. While some dissolved solids are naturally beneficial, excessively high or low TDS levels can affect the taste, quality, and usability of your water.

At Acuario, we believe TDS should be considered alongside other water quality indicators, as it does not tell you everything about whether your water is safe to drink.

What Does Total Dissolved Solids Mean?

Total dissolved solids refers to the concentration of dissolved substances that remain in water after solids have dissolved completely. These substances are so small that they cannot be removed by a simple sediment filter.

Common dissolved solids include:

• Calcium
• Magnesium
• Sodium
• Potassium
• Bicarbonates
• Chlorides
• Sulfates
• Nitrates
• Trace metals

Some of these minerals occur naturally as water passes through rocks and soil, while others may come from municipal treatment, agricultural runoff, industrial activity, or aging plumbing.

How Is TDS Measured?

Total Dissolved Solids are measured in parts per million (ppm) or milligrams per litre (mg/L). A TDS meter estimates the concentration of dissolved ions by measuring the electrical conductivity of the water.

Although a TDS meter provides a quick indication of mineral content, it cannot identify which dissolved substances are present. Two water samples with the same TDS reading may have completely different water quality depending on the source of those dissolved solids.

What Is a Good TDS Level?

There is no single “perfect” TDS level, but these general guidelines are commonly used:

High TDS does not automatically mean water is unsafe, and low TDS does not always mean it is healthier. The type of dissolved solids is often more important than the total amount.

Does High TDS Mean Contaminated Water?

Not necessarily.

A high TDS reading may simply indicate naturally occurring minerals such as calcium and magnesium, which contribute to healthy drinking water. However, elevated TDS can also result from unwanted substances including sodium, nitrates, heavy metals, or industrial contaminants.

Likewise, water with a very low TDS reading may still contain bacteria, viruses, pesticides, or chemicals that a TDS meter cannot detect.

For this reason, TDS should always be evaluated alongside comprehensive water testing.

Should You Test Your Water?

If you notice changes in taste, odor, scaling, staining, or water quality, testing your water is the best way to understand what’s present.

A TDS reading provides useful information about the overall mineral content of your water, but it should not be used as the only measure of water safety. Comprehensive water analysis can identify specific contaminants and help determine the most appropriate treatment solution for your home or business.