BrewWater
What is total alkalinity in water?
- total alkalinity in water
- Total alkalinity is the capacity of water to neutralise acid without its pH falling, conventionally expressed as milligrams per litre of calcium carbonate equivalent.
Short answer
Total alkalinity measures how much acid water can neutralise before its pH falls, reported as milligrams per litre of calcium carbonate equivalent. In brewing it buffers the acids coffee releases, so low alkalinity tastes sharp and sour while high alkalinity flattens acidity. The published target is forty.
| Measure | Value | Unit | Source |
|---|---|---|---|
| Target total alkalinity for brewing water | 40 | mg/L as CaCO3 | Specialty Coffee Association of America · verified |
| Bicarbonate content of sodium bicarbonate by mass | 72.63 | % by mass | IUPAC Commission on Isotopic Abundances and Atomic Weights · verified |
Why is alkalinity expressed as calcium carbonate?
The buffering is actually done by bicarbonate, but the convention is to report the equivalent mass of calcium carbonate instead. That adds a conversion step whenever you dose bicarbonate deliberately: one mole of bicarbonate buffers as half a mole of calcium carbonate, so forty milligrams per litre as calcium carbonate is about forty-nine milligrams per litre of actual bicarbonate.
What happens when alkalinity is too low?
With little buffering, the acids coffee releases during extraction move the pH freely and the cup reads sharp and sour. This is the usual complaint about brewing with distilled or reverse osmosis water straight, and it is a separate problem from the corrosion risk that the same water carries.
What happens when alkalinity is too high?
High alkalinity neutralises the acidity that gives coffee its brightness, so the cup flattens out and reads dull or chalky. Because carbonate alkalinity is also what precipitates as scale when heated, high alkalinity is simultaneously a flavour problem and a machine problem.