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.

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 (沸泉, fèiquán): 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

Which bottled water brands work well for tea in Europe? Volvic (TDS ~109 mg/L) is widely available and works well for most teas. Evian (TDS ~357 mg/L) is too high — it dulls lighter green and white teas noticeably. Buxton (~280 mg/L) is borderline. San Pellegrino (~1,000 mg/L) is too hard for any fine tea. For delicate teas, low-mineral waters like Spa Reine (~27 mg/L) or Volvic work best; for roasted oolongs and pǔ'ěr, slightly higher mineral content (100–150 mg/L) adds body without flattening. Check labels for TDS or "dry residue at 180°C."

Does a Brita filter make tap water good enough for tea? Yes for chlorine removal — activated carbon filters eliminate chlorine effectively, which is the primary concern for fine teas. The limitation: Brita's ion-exchange resin softens hard water only moderately and has a short-lived effect. In soft-water areas (TDS < 200 mg/L), Brita-filtered water works well. In very hard water areas (TDS > 300 mg/L), Brita alone is insufficient — supplement by blending with low-TDS bottled water or use a reverse osmosis filter with remineralisation.

Does the kettle material affect the water? Measurably, yes — though the effect varies. Cast iron kettles (铁壶, tiěhú) and clay/silver kettles (银壶, yínhú; 陶壶, táohú) soften the water's mouthfeel slightly and reduce perceived astringency; this is documented in traditional Chinese and Japanese tea literature. Stainless steel is neutral — no effect. Plastic kettles can leach subtle flavour compounds, particularly when new; this diminishes with use. For fine teas, stainless steel or glass is the practical choice if you don't use a traditional kettle.

What should I do if I only have hard tap water? Two practical approaches: (1) blend hard tap water with low-TDS bottled water in roughly 1:1 ratio — this cuts hardness by half without going to zero minerals; (2) use a carbon filter to remove chlorine, then accept some flavour dulling — hard water brews are still enjoyable, just less refined. Avoid: adding lemon juice to "soften" (this only acidifies, it doesn't reduce mineral content). For regular fine-tea brewing in a hard water area, a small reverse osmosis unit with a remineralisation cartridge is the long-term investment.

Does water temperature matter for cold brewing? Cold brewing (冷泡, lěng pào) is specifically defined by using cold or room-temperature water — no heating at all. Temperature matters in a different way: colder water (fridge, ~4°C) produces a slower, sweeter extraction over 6–8 hours, preferentially pulling amino acids over catechins. Room temperature (~20°C) extracts faster and produces slightly more body. Both work; fridge extraction gives the cleanest, sweetest result for green and white teas.