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Total Dissolved Solids

What is Total Dissolved Solids (TDS)?

TDS is used as a general indicator of water quality.

As the name describes, TDS tests measure the amount of all dissolved solids in the water. These solids are primarily minerals/salts, but can also include organic matter.

Where does TDS come from?

The amount of TDS in the water depends on where the water comes from.

Water that passes through soils high in soluble salts or minerals have higher TDS levels. Also, higher TDS levels occur when water receives agricultural or urban run-off.

Symbol for Minerals
Symbol for Organic Elements
Symbol for Salts

How does TDS affect my health?

Federal guidelines (i.e. non-mandatory standards) recommend that TDS levels do not exceed 500 parts per million (ppm).

There are no known health risks associated with TDS. Instead, people have done health research on individual constituents that make up TDS, such as nitrate, calcium, and organic matter.

TDS standards are set for "aesthetic" purposes, like taste and odor, not health purposes. People generally rate water as tasting "excellent" when TDS is around 300 ppm.

Q: What did Tucson's water tasting
survey data show?

Girl Drinking Water


Southwest Environmental Health Sciences Center
University of Arizona College of Pharmacy, Room 244
PO Box 210207, Tucson, AZ, USA 85721-0207

Funded by NIEHS grant # ES06694

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Last update: November 10, 2009
Page Content: Stephanie Nardei
Webmaster: Stephanie Nardei