Water makes up more than 98% of a pour-over and about 90% of an espresso. The specialty coffee industry pays more attention to coffee origin and roast. However, as a underestimated variable, water will destroy a cup of coffee even though you choose the best coffee beans.

Why Water Is Underestimated Variable in Specialty Coffee

Water Is a Participant in Coffee Extraction

In 2014, Christopher Hendon, a computational chemistry professor at the University of Oregon, and Maxwell Colonna-Dashwood, the then UK Coffee Champion, co-authored Water for Coffee, systematically revealing how water chemistry shapes extraction. They found:

Calcium and magnesium ions are natural extractants. They bind to organic acids, sugars and aromatic compounds in coffee grounds and blend into the liquid. Magnesium is especially efficient at extracting fruity acids, which is why water with balanced magnesium often makes coffee taste brighter.

Bicarbonate is an acid buffer. Too much alkalinity reduces acidity, leading to a flat taste while too little leaves acidity sharp and unbalanced.

Pure water extracts worst of all. With no minerals to participate, flavor turns bland. Therefore, in the condition of same beans, same grind size, same water temperature, when the water is changed, the flavor of coffee will be totally different.

What Does the SCA Water Standard Recommend ?

The Specialty Coffee Association (SCA) sets clear, measurable targets for brew water. The chart is as below:

Parameter	SCA Recommended Range	Target Value	Impact of Deviation
Total Dissolved Solids (TDS)	75–250 mg/L	~150 mg/L	Too low → watery, flat taste; Too high → bitter, muddy
Total Hardness (Ca & Mg)	50–175 mg/L (as CaCO₃)	~68 mg/L	Too low → under-extraction; Too high → scaling, over-extraction
Alkalinity (Bicarbonate)	40–75 mg/L (as CaCO₃)	~40 mg/L	Too high → acidity suppressed; Too low → sharp acidity
pH	6.5–7.5	7.0	Too acidic or too alkaline → unbalanced
Residual Chlorine	0 mg/L	0	Any presence → chemical off-flavors

This standard is based on extensive cupping trials and industry validation. It is the recognized reference to evaluate water in specialty coffee.

Why Is Water Quality the Blind Spot for Coffee Businesses ?

◉For coffee chains: Water varies enormously between city branches. The same recipe can taste bright in a soft-water city and bitter in a hard-water one. It will be a challenge for some stores with a promise "same cup every time".

◉For coffee roasters: The curve a roaster perfects often differs between the cupping water and the customer's actual brew water. Giving clients water advice is becoming a mark of differentiated service.

◉For coffee equipment brands: Hard water scales metal lines and shortens equipment life.

◉For premium kitchenware brands: Certain metal materials can subtly affect flavor in specific water conditions. That's a variable that cannot be ignored in product design and after-sales maintenance.

3 Steps Help You Control Water Quality

Here are 3 steps for you to control water, including measuring your baseline, filtering, and choosing inert brewing gear. Each step removes one variable from the cup.

1. Testing: Use a TDS pen and hardness test strips to learn your water baseline. Most city tap-water quality reports are also publicly available.

2. Filter: Activated-carbon filters remove chlorine and odors; reverse-osmosis (RO) systems precisely control TDS.

3. Material Choosing: The material of coffee maker is also important. Ceramic is extremely chemically inert. It does not react with water minerals and does not release metal ions. So the coffee maker itself never changes the water's chemistry, whether you use softened or remineralized water.

Why Does Brewing Tools Material Matter for Water ?

Once water is dialed in, coffee maker should not become a new variable. Premium ceramic is chemically inert. Using ceramic coffee makers plays an important role in everyday brewing.

Using ceramic French press and ceramic pour-over coffee maker is a ideal choice for home barista or coffee business. Whether you brew at home or run a coffee chain or specialty brand, that stability matters.