What Is TDS in Water?

TDS stands for total dissolved solids, and the EPA’s secondary drinking water standard for it is 500 mg/L. Secondary standards cover 15 contaminants and are non-mandatory guidelines to help public water systems manage drinking water for aesthetic considerations such as taste, color and odor, and the EPA says these contaminants are not considered to present a risk to human health at the secondary level.

Above 500 mg/L, the EPA lists hardness, deposits, colored water, staining and a salty taste as the noticeable effects of total dissolved solids. It says secondary contaminants above their standards may make water appear cloudy or colored or taste or smell bad, and that federal regulations do not require public water systems to monitor or treat for them, though state health agencies and water systems often decide to.

For removal, the EPA says non-conventional treatments like distillation, reverse osmosis and electrodialysis are effective for removing total dissolved solids and other inorganic substances, though they are fairly expensive. To find out about your water, it suggests identifying your public water system, asking which secondary contaminants it monitors and whether the water meets the secondary standards, and asking for a copy of the monitoring results.

Sources checked September 15, 2026. Every point below links the page it came from.

The sources behind this answer

  • Regulatory filingThe EPA says its National Secondary Drinking Water Standards set non-mandatory water quality standards for 15 contaminants, as guidelines for aesthetic considerations such as taste, color and odor. US EPA ↗
  • Government sourceThe EPA says the contaminants with secondary standards are not considered to present a risk to human health at the secondary maximum contaminant level. US EPA ↗
  • Regulatory filingThe EPA’s secondary maximum contaminant level for total dissolved solids is 500 mg/L, with hardness, deposits, colored water, staining and a salty taste listed as noticeable effects above it. US EPA ↗
  • Regulatory filingThe EPA says federal regulations do not require state health agencies and public water systems to monitor and treat for secondary contaminants, although they often decide to. US EPA ↗
  • Government sourceThe EPA says distillation, reverse osmosis and electrodialysis are effective for removing chloride, total dissolved solids and other inorganic substances, but are fairly expensive technologies. US EPA ↗
  • Government sourceThe EPA suggests people concerned about secondary contaminants identify their public water system, ask which secondary contaminants it monitors, and ask for a copy of the monitoring results. US EPA ↗

Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.

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