BrewWater
What is total dissolved solids (TDS) in water?
- total dissolved solids (TDS) in water
- Total dissolved solids is the combined mass of all dissolved substances in water — minerals, salts and organic matter — reported in milligrams per litre.
Short answer
Total dissolved solids is the combined mass of everything dissolved in water, reported in milligrams per litre. It counts minerals, salts and organics together, so it describes how much is present rather than what. Brewing targets one hundred and fifty, accepting seventy-five to two hundred and fifty.
| Measure | Value | Unit | Source |
|---|---|---|---|
| Target total dissolved solids for brewing water | 150 | mg/L | Specialty Coffee Association of America · verified |
| Acceptable total dissolved solids range for brewing water | 75–250 | mg/L | Specialty Coffee Association of America · verified |
Is TDS the same as hardness?
No, and conflating them is the most common mistake in this subject. Hardness counts only the polyvalent cations, predominantly calcium and magnesium. Total dissolved solids counts those plus sodium, chloride, sulfate and everything else in solution. Water can sit perfectly inside the TDS range and still be far outside the hardness range.
Why do two meters disagree about the same water?
Most handheld meters do not measure dissolved solids at all. They measure electrical conductivity and multiply by a conversion factor to estimate TDS. The brewing standard footnotes that its figures assume a 4-4-2 conversion, so a meter using a different factor will report a different number for identical water.
Can TDS be too low?
Yes. Extraction needs dissolved mineral content to work with, and water stripped of it produces a thin, hollow cup. The World Health Organization notes separately that demineralised water tastes flat, which is why producers of demineralised bottled water add minerals back before selling it.