How to Test Total Dissolved Solids in Well Water
Total dissolved solids measure the combined minerals and salts in your water. Testing helps explain taste issues, though TDS alone is not a safety test.
Quick Answer
Total dissolved solids (TDS) is the combined amount of minerals, salts, and metals dissolved in your water. The EPA secondary (aesthetic) guideline is 500 mg/L. High TDS can cause a salty, metallic, or bitter taste, but a TDS number alone does not tell you whether specific contaminants are safe.
What TDS can and cannot tell you
TDS is a bulk measurement of everything dissolved in the water, from harmless calcium to substances you would want to limit. A high reading signals that something is elevated, but it does not identify what. A low TDS reading does not mean the water is safe, since some harmful contaminants are dangerous at levels too small to move a TDS meter.
A TDS meter is only a screen
How to test TDS
- 1Use a calibrated TDS meter for a quick at-home estimate, or a laboratory for an accurate measurement.
- 2Compare the result to the 500 mg/L secondary guideline.
- 3If TDS is high or the taste is off, order a full lab panel to find the specific contributors.
- 4Treat the cause, not just the symptom, based on the detailed results.
Think of TDS as a starting clue. If it is elevated, the next step is a detailed laboratory panel to find out which minerals or contaminants are responsible.
Frequently asked questions
- Does low TDS mean my water is safe to drink?
- No. TDS does not measure bacteria or trace contaminants like arsenic and lead. A low TDS reading cannot confirm safety; only a laboratory health panel can.
Sources & references
- Secondary Drinking Water Standards: Guidance for Nuisance Chemicals — US EPA, accessed October 29, 2026
- Well Testing — CDC, accessed October 29, 2026
This guide is documentary research and general information, not a laboratory analysis or professional assessment of your specific well. See our disclaimer.