What is the ideal TDS for specialty coffee?

The Specialty Coffee Association (SCA) recommends a target Total Dissolved Solids (TDS) of 150 ppm (acceptable range: 75 to 250 ppm) with zero chlorine and a neutral pH of 7.0.

What is the difference between GH and KH in coffee water?

General Hardness (GH) measures dissolved calcium and magnesium ions which bind to flavor compounds and pull them from coffee grounds. Carbonate Hardness (KH or Alkalinity) measures bicarbonate ions which act as a chemical buffer to neutralize acids.

Why shouldn't I brew with pure distilled or RO water?

Water with 0 TDS lacks the mineral ions (calcium and magnesium) needed to bond with the aromatic coffee compounds, resulting in flat, sour, hollow, and drastically underextracted coffee.

The Brew App • Advanced Water Science

Coffee Water Chemistry & Extraction Yield Guide

Your brewed cup is 98.5% water. Discover how magnesium, calcium, and bicarbonate alkalinity dictate your extraction yield, cup clarity, and brightness.

1. The SCA Water Standard Target Specification

The Specialty Coffee Association defines exact physical and chemical metrics required to extract balanced solubles from roast coffee beans without corrosion or scale buildup.

Target TDS

150 PPM

Range: 75 – 250 PPM

General Hardness (GH)

68 PPM

CaCO3 equivalent (50-175)

Alkalinity (KH)

40 PPM

Buffer CaCO3 (target 40)

Target pH

7.0

Range: 6.5 – 7.5

2. Mineral Breakdown: What Each Ion Does

Magnesium (Mg²⁺): Has high charge density that bonds aggressively with oxygen-rich organic acids and aroma volatiles. Crucial for pulling crisp floral and citrus notes in washed African lots.
Calcium (Ca²⁺): Bonds moderately with heavier aromatic compounds, emphasizing body, creamy mouthfeel, and chocolate/caramel sweetness.
Bicarbonate Buffer (HCO₃⁻): Neutralizes excess hydrogen ions. Too little buffer makes the cup sour and harsh; too much buffer flattens acidity and makes coffee taste dull and chalky.

3. Formulated Water Recipes

Light Roast Brightness (Filter / V60)

Optimized for delicate washed Ethiopians, Kenyans, and Geishas with high fruit clarity.

Lotus Drops (per 1L): 4 drops Magnesium • 1 drop Calcium • 1 drop Bicarbonate • 0 drops Potassium

Balanced Daily Cup (SCA Benchmark)

All-rounder profile suited for medium roasts, South American washed coffees, and blends.

Lotus Drops (per 1L): 3 drops Magnesium • 2 drops Calcium • 2 drops Bicarbonate • 1 drop Potassium

Sweet & Heavy Espresso (High Extraction)

High buffer and high calcium for thick crema, muted sharp bitterness, and prolonged finish.

Lotus Drops (per 1L): 2 drops Magnesium • 4 drops Calcium • 3 drops Bicarbonate • 1 drop Potassium

4. Off-The-Shelf Bottled Waters Evaluated Against SCA Standards

If you prefer buying ready-to-brew water from the grocery store without mixing mineral drops, these commercial bottled waters have been laboratory-tested and evaluated against the SCA target window:

Crystal Geyser Alpine Spring Water (Mt. Shasta, CA) Specialty Gold Standard

115 PPM TDS • 50 GH • 52 KH • pH 7.2. The #1 recommended grocery store water in US specialty coffee. Ready to pour straight into your kettle with zero remineralization.

Volvic Natural Spring Water (Puy de Dôme, France) European Barista Benchmark

130 PPM TDS • 62 GH • 58 KH • pH 7.0. Filtered through volcanic rock with 31.7 mg/L natural silica for velvety mouthfeel and sparkling cup clarity.

Evian Natural Spring Water (Évian-les-Bains, France) Requires 50/50 Dilution

357 PPM TDS undiluted (too hard). Mix 50/50 with steam-distilled water to yield an exceptional 178 PPM brew water at low cost.

Poland Spring 100% Natural Spring Water (Maine, USA) Soft / Nordic Light

50 PPM TDS • 26 GH • 20 KH • pH 6.8. Naturally very soft water that allows intense floral and berry acidity to shine through without bicarbonate neutralization.