Total dissolved solids (TDS) are the amount of organic and inorganic materials, such as metals, minerals, and ions, dissolved in a particular volume of water. When a solvent, such as water, encounters soluble material, particles of the material are absorbed into the water. TDS in water can come from just about anywhere, including minerals in springs from a water source, chemicals used to treat the water supply from sewage systems, runoff from road salts and yard chemicals or fertilizers, even the plumbing in your home.

Testing your water using a TDS meter is the easiest way to measure for total dissolved solids. Some filtration systems are equipped with a TDS meter to monitor the levels periodically.

TDS meter is a small hand-held device used to indicate the Total Dissolved Solids in a solution, usually water. Since dissolved ionized solids, such as salts and minerals, increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that reading.

Total dissolved solids (TDS) is measured as a volume of water with the unit milligrams per liter (mg/L), otherwise known as parts per million (ppm). According to the EPA secondary drinking water regulations, 500 ppm is the recommended maximum amount of TDS for your drinking water. Anything measurement higher than 1000 ppm is an unsafe level of TDS. If your TDS reading exceeds 2000 ppm, then a filtration system may be unable to handle it.