Our head roaster explores the water parameters that matter most for coffee and tea, explains the chemistry behind them, and shares practical tips for optimising your water at home.

Water makes up 98-99% of your final cup. Water isn’t just a neutral medium; it’s an active participant in extraction. Its mineral content and chemical makeup can enhance or suppress flavour, alter body and texture, and even shift perceived acidity.

Key Parameters

Water is much more than just H2O. Most drinking water contains a range of minerals and organic compounds, in varying levels depending on where you live and the source of your water. These dissolved substances influence everything from solubility to flavour perception.

To understand how water chemistry impacts flavour, we’ll focus on two critical metrics: general hardness and alkalinity.

General Hardness (GH)

This represents the total concentration of cations (positively charged ions) present; for coffee and tea, this is primarily Calcium and Magnesium.

• Calcium (Ca²⁺) and Magnesium (Mg²⁺) act as co-solvents in the extraction of flavour compounds, particularly acids, oils and aromatic molecules.

• These cations can enhance flavour clarity and body when present at optimal levels.

• However, excess hardness can leave your brew with a chalky texture and a flat, muddied taste.

Ideal range for coffee: 50-175 ppm

Ideal range for tea: 40-80 ppm

Alkalinity (KH), aka Carbonate Hardness

Alkalinity, or carbonate hardness, is a measure of the water’s ability to neutralise acids. In brewing, this is primarily from bicarbonate ions (HCO₃⁻).

• Bicarbonate acts as a pH buffer, neutralising acids extracted during brewing.

• High alkalinity dampens acidity, leading to a flatter flavour profile.

• Low alkalinity allows the expression of brighter, fruitier, or more floral notes—but may also result in an unbalanced or sour taste if not carefully managed.

Ideal range for tea: 20-60 ppm as CaCO₃, preferably towards the lower end, especially for green or white teas.

Water Standards for Brewing

For coffee, the Specialty Coffee Association (SCA) recommends:

pH: 6.5-7.5

TDS: 150-175 ppm

General Hardness: 50-175 ppm

Alkalinity: 40-75 ppm as CaCO₃

Clarity Clear colour, no chlorine or bad smell

For tea, the Tea Association of the USA recommends:

pH: 6-8

TDS: 50-150 ppm

General Hardness: 40-80 ppm*

Alkalinity: 20-60 ppm as CaCO₃

*Most tea experts recommend the softer end of this range. One study found mountain spring water (20ppm) produced the best results for tea.

Testing Your Water Quality

To improve your brewing, it’s essential to know what’s in your water. Many water companies provide a water quality report, which usually includes the hardness levels in your area. If not, you can use water hardness test strips (commonly used for ponds or aquariums) to check your water’s hardness. For ultimate precision, consider sending a water sample to a third-party laboratory for analysis.

Improving Your Brewing Water

1. Tap Water 

If you’re lucky, your tap water might already be in the sweet spot for brewing. Some areas have naturally optimal water for brewing coffee and tea, which can be elevated using an active carbon stick to remove impurities.

2. Filtered Water

Most carbon-based filters remove impurities, but they don’t change the mineral content of the water significantly. If your area has moderately hard water, an on exchange filter might help. These soften your water to an optimal level, with some products also re-mineralising with magnesium to enhance flavour.

3. Bottled Water

Bottled water is a quick and convenient option, but it can get expensive and have a significant environmental impact. If you go this route, avoid mineral waters that are too high in calcium and magnesium. Instead, look for low-mineral or filtered waters, which often provide a more consistent base for brewing.

4. DIY Water Recipes

If you’re the adventurous type, you can take control of your water by buying distilled water and adding minerals yourself. Recipes for creating brewing water can be found online, and they let you tailor the mineral content to exactly what you want for your brew. This can be a cost-effective and precise solution.

Water may be the most overlooked aspect of brewing, but it’s just as important as the beans or leaves themselves. By understanding your water’s composition and making some simple adjustments, you can elevate your coffee and tea to new heights.