Total dissolved solids (TDS) refers to the amount of minerals, metals, organic material and salts that are dissolved in a certain water volume that is expressed in mg/L. It is directly associated with the quality and purity of water, particularly in water purification systems.

Total dissolved solids may be suspended in forms such as:

• Molecular
• Ionized
• Micro-granular (colloidal sol)

The levels of total dissolved solids affect all that lives in, drinks or uses water. Thus, it needs to be measured to ensure the quality of drinking water and the performance in industrial settings involving pipes, valves and other equipment.