Water for Tea — Temperature and Quality

Tea is approximately 99% water by weight. Water quality and temperature are the two variables most beginners neglect and most experienced drinkers obsess over. A fine tea brewed in the wrong water produces a flat, harsh, or lifeless cup; average tea brewed in good water at the right temperature often exceeds expectations.

Lǔ Yǔ (陆羽), the Táng dynasty tea sage, wrote in the Chá Jīng (茶经, 780 CE): "Mountain spring water is best; river water next; well water worst." The same principle holds today — natural filtration through rock and mineral layers produces the ideal brewing water.

What TDS level is best for tea?

TDS (Total Dissolved Solids) measures mineral content in mg/L. The sweet spot for tea is 50–150 mg/L:

• Below 50 mg/L (distilled, RO-filtered without remineralisation): flat, lifeless brew — minerals carry flavour compounds and affect extraction chemistry
• 50–150 mg/L: optimal range; clean, complete extraction
• 150–200 mg/L: acceptable; flavour begins to show some dulling
• Above 200 mg/L: hardness dulls aroma; produces flat or chalky taste
• Above 300 mg/L: calcium and magnesium interfere with polyphenol extraction; tannins become harsh

Practical recommendations (in order of preference):

1. Still mineral water with TDS 80–150 mg/L (check the label)
2. Filtered tap water (activated carbon removes chlorine)
3. Tap water left open 30+ minutes (allows chlorine to dissipate)
4. Avoid: distilled, RO without remineralisation, tap water TDS > 300 mg/L

Chlorine note: Most European tap water contains residual chlorine. Chlorine kills volatile aromatic compounds — it will noticeably degrade a fine green or white tea. Carbon filter or 30-minute open-air rest eliminates it.

Historically, Huì Quán (惠泉) spring water from Wúxī, Jiāngsū — with a TDS of approximately 120 mg/L — was considered the ideal water for tiě guānyīn. The 8th-century classification by Lǔ Yǔ placed it in the top tier of Chinese spring waters.

TL;DR: TDS 80–150 mg/L is the target. Filter out chlorine. Avoid distilled (too low) and hard water (too high). A variable-temperature kettle + filtered tap water at the right TDS = practical optimum for home brewing.

Temperature by tea type

Water temperature controls which compounds are extracted and at what rate. Lower temperatures suppress bitter catechins and preserve volatile aromatics; higher temperatures extract everything more rapidly.

If-then rule: If brewing rock oolong below 95°C → flat, woody result with no mineral character. If brewing green tea above 85°C → harsh, bitter, aromatic compounds destroyed.

Measuring without a thermometer: Boil water fully, then cool. 100°C → 80°C takes roughly 3–4 minutes in an open vessel; 100°C → 70°C takes 6–8 minutes. A variable-temperature kettle is the highest-ROI tea equipment purchase.

The boiling question

The boiling stages: Watching a traditional kettle, distinct bubble stages appear before full boil:

• Shrimp eyes (虾眼 xiā yǎn): tiny bubbles forming at bottom, ~70°C
• Crab eyes (蟹眼 xiè yǎn): larger bubbles, ~80°C
• Fish eyes (鱼眼 yú yǎn): clusters rising, ~85°C
• Full rolling boil: 100°C at sea level

These stages align approximately with target brewing temperatures for different tea types — useful if using a traditional kettle without temperature display.

Re-boiling: Repeatedly boiled water concentrates dissolved minerals and loses dissolved oxygen. Traditional Chinese tea culture considers repeatedly-reboiled "dead water" (死水 sǐshuǐ) inferior for fine teas. For daily use the effect is minimal; for delicate green and white teas, use freshly drawn and freshly boiled water.

Altitude

Water boils at approximately 1°C lower per 300 m of altitude elevation. Practical implications:

• 1,500 m → water boils at ~95°C
• 3,000 m → water boils at ~90°C

If brewing pǔ'ěr or roasted oolongs requiring 100°C at altitude → a pressurised kettle is the only solution. At sea level or moderate elevation (< 1,000 m), altitude is irrelevant.

Related

• Gōngfū Brewing Guide
• Gàiwǎn
• How to Store Tea

FAQ

What TDS should water for tea be? 50–150 mg/L is the ideal range. Below 50 (distilled, RO-filtered) = flat and lifeless. Above 200 = dulls aroma and introduces chalky harshness. Check bottled mineral water labels; most European spring waters fall in the 80–200 mg/L range.

Does tap water affect tea quality? Yes — primarily through chlorine, which destroys volatile aromatics. Filter with activated carbon or leave in an open container for 30+ minutes before boiling. In very hard water areas (TDS > 300 mg/L), a carbon filter or blending with low-mineral water helps significantly.

What temperature should I use for green tea? 75–80°C. Above 85°C destroys the volatile aromatic compounds responsible for green tea's character and increases extraction of bitter catechins from tender buds. Use a variable-temperature kettle or let boiled water cool for 3–4 minutes before pouring.

What are shrimp eyes and fish eyes in tea? These are traditional Chinese terms for bubble stages before full boil: shrimp eyes (~70°C), crab eyes (~80°C), fish eyes (~85°C). They provide approximate temperature guidance when brewing with a traditional kettle without a temperature display.

Why does tea taste different at high altitude? Water boils at lower temperatures as elevation increases — approximately 1°C lower per 300 m. At 1,500 m, water only reaches ~95°C, which is insufficient for teas requiring a full boil. A pressurised kettle solves this for high-altitude brewing.