Water is part of the recipe

Before changing the leaves, try the water

Water can change a tea’s colour and perceived bitterness.^[1][2] Our suggestion: before dismissing a tea—or extending the steep to find a missing flavour—compare it in another water.

Research across six Chinese tea categories found that the higher-pH, higher-mineral waters tested generally produced darker infusions with lower sensory scores. Green tea was particularly sensitive.^[1] Those results do not establish one perfect water for every tea: several properties changed together, and Rou Gui deserves its own tasting.

Read beyond the mineralisation number

Dissolved-solids measurements depend on the method used.^[3] For that reason, we preserve the label’s wording—TDS, total mineralisation or dry residue—and its measurement basis rather than treating every total as interchangeable.

A conductivity-based TDS reading is an estimate; it does not measure the concentration of each mineral.^[4] Use the bottle label or producer’s analysis for bicarbonate, calcium and magnesium. We recommend recording the source and analysis date alongside the values, and checking the current bottle when you buy.

• Mineralisation: keep the declared value, unit and measurement basis.
• Bicarbonate, calcium and magnesium: record each separately in mg/L.
• Alkalinity and hardness are different measurements.^[5] Preserve “as CaCO₃” when that is how they are reported.

Bicarbonate changes the balance

Bicarbonate contributes to alkalinity: water’s capacity to neutralise acids. The starting pH on a bottle does not tell you how strongly the water will resist a change in pH.^[8]

In controlled green-tea experiments, alkaline conditions promoted browning and changes in catechins remaining in the infusion.^[6] A 2026 sensory study also found that bicarbonate changed aroma, brightness and taste, with results depending on concentration and tea type.^[7] Its numerical thresholds describe those experiments; they are not universal pass-or-fail limits for bottled water.

Calcium and magnesium are part of a mixture

Calcium and magnesium contribute to water hardness.^[9] Tea polyphenols can form a surface film with ions from the water; the water composition and tea variety affect its properties.^[10]

Our reading of these findings: they do not justify a simple promise that magnesium adds sweetness or calcium spoils tea. We suggest comparing the complete water profile and the resulting cup rather than assigning a flavour to one mineral or transferring a coffee-water formula directly to tea.

Our suggested starting range

For a first comparison, we suggest still, unflavoured drinking water with roughly 30–150 mg/L declared TDS or dry residue, preferably below about 50 mg/L bicarbonate when that value is available. This is our editorial starting range, not a scientifically established optimum. Record calcium and magnesium without treating either as a flavour score.

Waters outside this range can make a cup you prefer. Very low-mineral water can work well too, but it does not necessarily make a gentler infusion: a controlled study found greater bitterness in green tea brewed with more purified water.^[11] More extraction and more enjoyment are different aims.

Our suggested comparison

Brew equal leaf weights in two comparable vessels, with the same water volume, temperature and timing. Change only the water. Taste both as they cool, comparing aroma, body, bitterness, drying sensation and finish. Repeat with another tea before making a general judgement.

“Wrong water” means water that works poorly for the cup you want. Muted aroma or a persistent drying sensation gives you a reason to compare, not a diagnosis of one mineral. Once you find a water you enjoy, keep it consistent while learning the tea.

On a tea page, a recorded water profile identifies the water associated with the recipe. We label proposed pairings as proposals; a bottled-water analysis by itself does not mean we have tasted that tea with it.