Make sense of brewing water.

Measure the starting water first

Choose stock additions to reach a hardness/alkalinity target, or blend two potable waters to reduce mineral concentrations. Use measured GH and alkalinity in mg/L as CaCO₃; pH and a TDS meter cannot substitute for these two measurements. Retest the finished mixture. Starting composition, stock purity and measurement uncertainty limit the prediction.

Stock mode solves both mineral balances at the final volume, including the displacement of starting water by the stocks. For 1 L, starting at GH 30/KH 20 and targeting GH 80/KH 40, use about 52.21 ml hardness stock, 21.47 ml buffer stock and 926.32 ml starting water. Simply subtracting starting values would incorrectly ignore that dilution. In blend mode, equal volumes of GH 200/KH 100 water and GH 0/KH 0 water predict GH 100/KH 50. You cannot independently change their hardness-to-alkalinity relationship by dilution alone.

Read a bottle mineral label

The label mode converts stated calcium and magnesium to hardness using their molar masses, and bicarbonate to alkalinity using equivalent weights. It assumes bicarbonate dominates the alkalinity. Do not enter a number labeled “alkalinity as CaCO₃” into the bicarbonate field. A missing ion is unknown; the defaults are illustrative zeros, not a claim about a bottle. Label averages are starting estimates; confirm GH/KH with a suitable test. Copy the estimates into mixing mode when appropriate.

Prepare the two stocks precisely

In separate clean, labeled containers, dissolve 2.4626 g food-grade magnesium sulfate heptahydrate (MgSO₄·7H₂O) and top up with suitable potable demineralized water to a final 1 L; dissolve 1.6787 g food-grade sodium bicarbonate (NaHCO₃) and similarly top up to a final 1 L. These stocks supply approximately 1,000 mg/L CaCO₃-equivalent hardness or alkalinity respectively. Use an appropriately precise scale and dosing equipment; do not use bath salts or substitute ingredient forms. The tool rejects nonzero stock doses below 1 ml. They are concentrates, not drinking water.

These calculations assume additive volumes and those stock concentrations. Existing calcium remains in the starting-water portion; the hardness stock adds magnesium only. No dissolved-solids total, pH, potability or taste score is inferred. Make small clean batches, label ingredients and preparation dates, follow food-handling instructions and avoid contamination.

Recipe and mixing-method reference: Barista Hustle water recipes. Our simultaneous target solver is mass-balance arithmetic; it does not endorse one target as ideal.