In a tasting conducting by the Technical Standards Committee of the SCAA, coffee was brewed with different levels of TDS in order to determine if significant flavor differences existed and how much difference actually existed. The tasting was blind and was designed to isolate TDS as the key variable. The same coffee, grind and brewer were used and the same standard combination of minerals was used. The only difference between samples was the concentration of those minerals in the brewing water.
Three samples were prepared: one with 45 mg/L TDS, one with 150 mg/L TDS and one with 450 mg/L TDS. The coffee that was brewed with 150 mg/L water was chosen as far superior by all who judged the samples.
| Cupping Taste Test | Dissolved Solids in Water | Tasting Judging |
| 1 | 45 mg/L | Little body; tart taste |
| 2 | 150 mg/L | Rich, piquant, rounded taste |
| 3 | 450 mg/L | Imbalance of acidity and body, aroma off, harsher finish |
Based on these results, a second tasting was conducted using 125 mg/L, 150 mg/L and 175 mg/L samples. The goal of the second tasting was to determine if even slight variations in water quality would have an effect on flavor and extraction. These minor changes in TDS were unanimously discernable by the judging panel. Acid and body balances were perceived to be off at both 125 mg/L and 175 mg/L TDS, and the 150 mg/L brew was rated as superior.
