How Water Quality Affects the Taste of Tea and Coffee

Why Water Is More Than Just a Vehicle

Water makes up roughly 98–99% of a finished cup of tea or coffee. Yet most people spend far more time selecting their beans or leaves than thinking about the water carrying those flavors. The chemistry of your water determines how effectively aromatic oils, acids, and compounds are drawn out during brewing — and which ones end up in your cup.

Flavor extraction is a chemical process. Mineral ions in water act as carriers, latching onto soluble compounds in ground coffee or steeped tea leaves. When that mineral balance is off — either too sparse or too concentrated — extraction becomes uneven. The result is a cup that tastes noticeably thin, bitter, or just wrong in a way that's hard to pinpoint.

Water is also the factor most home brewers overlook when troubleshooting flavor. If you've dialed in your grind size and steep time but the cup still disappoints, your water may be the culprit. See our guide to common cold brew mistakes for a closer look at how water interacts with extraction variables.

The Role of Minerals: Hardness, Softness, and TDS

The two minerals most relevant to brewing are calcium and magnesium. Magnesium is particularly effective at extracting the aromatic compounds responsible for coffee's fruity and floral notes. Calcium plays a supporting role in extraction but, in excess, can make water taste chalky and interfere with the crispness of brewed tea.

Hard water — water with high mineral content, typically above 200 ppm TDS — often over-extracts, pulling bitter or astringent compounds that would otherwise remain in the grounds or leaves. It can also leave scale deposits in kettles and machines over time.

Soft water — very low in minerals, below roughly 50 ppm TDS — tends to under-extract, producing a flat, watery cup with little depth. Completely demineralized water, such as distilled water, performs worst of all: without mineral ions to facilitate bonding, even the best coffee or tea will taste lifeless.

For most brewers, a moderate mineral level in the 75–150 ppm TDS range produces the most balanced extraction — a figure supported by Specialty Coffee Association guidelines.

Chlorine, Chloramine, and Off-Flavors

Municipal water treatment in the US commonly uses chlorine or chloramine (a chlorine-ammonia compound) to make tap water safe to drink. These disinfectants do their job, but they also interact chemically with compounds in tea and coffee, producing off-flavors that range from a faint medicinal quality to a noticeably flat or plasticky taste.

Chloramine is more stable than chlorine and does not dissipate simply by leaving water to sit — it requires active filtration to remove. A carbon block or activated carbon filter, such as those found in standard pitcher filters or under-sink units, is effective at reducing both chlorine and chloramine before brewing.

If your tap water tastes or smells noticeably of chlorine, that same characteristic will carry into your brew. Running tap water through even a basic carbon filter is one of the most impactful, low-cost improvements a home brewer can make.

pH and Its Effect on Flavor Chemistry

Water's pH — its position on the acidic-to-alkaline scale — affects how certain flavor compounds dissolve and are perceived on the palate. Neutral water sits at pH 7.0. Most US tap water falls between 6.5 and 8.5, depending on source and treatment.

In coffee, the bright, fruity acidity that many specialty roasts are prized for comes from organic acids released during extraction. Alkaline water (pH above ~7.5) neutralizes some of these acids, suppressing the very brightness that makes those roasts interesting. The result can taste flat or one-dimensional.

Tea is similarly sensitive. Green and white teas — which are delicate and lower in tannins — are particularly affected by high-pH water, which can turn their color and dull their subtle flavors. Explore how tea processing affects flavor compounds to better understand why certain teas demand more careful water selection than others.

Tap, Filtered, and Bottled: A Practical Comparison

Understanding the differences between common water sources helps you make a confident everyday choice:

• Unfiltered tap water varies enormously by location. In some regions it brews surprisingly well; in others, chloramine and high hardness make it noticeably inferior. It's worth tasting your tap water on its own before assuming it's the problem — or assuming it's fine.
• Carbon-filtered tap water removes chlorine and chloramine and is the most practical upgrade for most households. It preserves the natural mineral content of your local water while eliminating the compounds most likely to introduce off-flavors. Results are consistent and cost-effective.
• Bottled water can range from excellent to counterproductive, depending on mineral content. Some brands are very soft, others are high in sodium. Checking the TDS figure on the label — or the brand's water quality report — gives you useful guidance before committing to a specific product.
• Filtered water systems (reverse osmosis, for example) can strip water too aggressively, removing beneficial minerals along with contaminants. If you use reverse osmosis water, adding a small amount of mineral content back in — through a remineralization filter cartridge — can restore brewing performance.

Water quality is just one variable in the overall brewing equation. Temperature also plays a meaningful role in how flavor compounds are extracted and how they're perceived in the final cup.