Total Dissolved Solids (TDS) measure all inorganic and organic substances dissolved in water, present in molecular, ionized, or micro-granular forms. Understanding TDS levels is important for assessing water quality and its suitability for various uses.
Understanding Total Dissolved Solids
Water, often called the universal solvent, readily dissolves various materials it encounters. TDS includes minerals, salts, metals, and organic matter. Common examples include calcium, magnesium, sodium, potassium, bicarbonates, chlorides, sulfates, and nitrates.
TDS in water originates from a variety of sources. Natural processes, such as water flowing over and through rocks and soil, dissolve minerals. Human activities also contribute through agricultural runoff, industrial discharges, urban runoff, and chemicals used in water treatment. Plumbing materials within homes can also add to the water’s dissolved solid content.
The presence of dissolved solids impacts water quality. High TDS levels can affect water taste, making it bitter, salty, or metallic. Conversely, very low TDS can taste flat or insipid due to the absence of dissolved minerals. Beyond taste, elevated TDS can lead to scale buildup in pipes, water heaters, and household appliances, potentially shortening their lifespan and reducing efficiency. TDS levels are also a consideration for specialized applications like maintaining aquariums or managing hydroponic systems, where specific ranges are necessary for aquatic life or plant health.
Measuring Total Dissolved Solids
Total Dissolved Solids can be measured through several methods. For most individuals, a handheld TDS meter offers a convenient and rapid way to assess water quality. These meters operate by measuring the electrical conductivity of water. Dissolved inorganic substances, such as salts and minerals, carry an electrical charge, allowing water to conduct electricity. The meter converts this conductivity measurement into a TDS value, typically expressed in parts per million (ppm) or milligrams per liter (mg/L), as these units are interchangeable.
Using a handheld TDS meter is straightforward. First, calibrate the meter according to manufacturer’s instructions for accuracy. Next, immerse the electrodes into the water sample, ensuring they are fully submerged without touching the container’s sides or bottom. Allow a few seconds for the reading to stabilize on the digital display. The displayed number represents the estimated TDS level. This method is popular due to its affordability, speed, and ease of use, providing an immediate reading of the water’s dissolved solid concentration.
The gravimetric method, primarily used in laboratories, offers a more precise way to determine TDS. This process involves evaporating a known volume of filtered water in a pre-weighed dish. After evaporation, the remaining solid residue is weighed. This direct measurement provides the most accurate TDS value. However, it is labor-intensive and time-consuming, making it impractical for routine home use.
Interpreting Your TDS Readings
Interpreting your TDS reading is important, as the ideal level varies depending on the water’s intended use. TDS levels in natural water sources range from less than 30 mg/L to several thousand mg/L. For drinking water, palatability links to TDS levels. Water with TDS below 300 mg/L tastes excellent. Levels between 300 and 600 mg/L are good, balancing mineral content and purity. The World Health Organization suggests water becomes unpalatable above 600 mg/L, and levels exceeding 1000 mg/L are poor quality or unacceptable due to taste. The U.S. Environmental Protection Agency recommends a maximum aesthetic guideline of 500 ppm for drinking water.
For specific applications, different TDS ranges are desired. In hydroponics, where plants receive nutrients through water, the ideal TDS range varies based on plant species and growth stage. For many hydroponic crops, 800 to 1500 ppm is suitable; young plants require lower levels, and mature plants tolerate higher concentrations. For household appliances, high TDS, particularly from hardness minerals like calcium and magnesium, can lead to scale buildup.
If your water’s TDS reading is high or low, further investigation may be warranted. While a high TDS reading does not automatically indicate unsafe water, it can suggest dissolved substances affecting taste, appearance, or leading to appliance issues. If specific contaminants are a concern, professional water testing can identify the exact composition of dissolved solids. For aesthetic or appliance-related issues, water treatment methods like reverse osmosis or distillation can effectively reduce TDS levels.