Water Quality Calculator

Evaluate your water's suitability for coffee brewing. Input TDS (total dissolved solids), pH, and mineral content to see how your water compares to SCA standards. Get recommendations for water treatment if needed.

Calculator

SCA Target vs Your Water

Too Hard?

Mix with distilled water or use a carbon filter. High mineral content mutes brightness.

Too Soft?

Add mineral drops (Third Wave Water, Lotus) to distilled or RO water for balanced extraction.

High Alkalinity?

Alkalinity buffers acidity, making bright coffees taste flat. Target 40-70 ppm KH.

How to Use

  1. 1
    Test or enter your source water

    Use a TDS meter or test strips to measure your tap water's mineral content, or enter approximate values if you know your municipal water report. Target minerals include calcium hardness, magnesium, sodium, and bicarbonate — each affects extraction and flavor differently.

  2. 2
    Compare to SCA water quality standards

    The SCA specifies target water for coffee brewing: total hardness 50-175 ppm, total dissolved solids 75-250 ppm, pH 6.5-7.5, and zero chlorine or chloramine. Review how your source water compares and which parameters fall outside the target range.

  3. 3
    Adjust your water chemistry

    Apply the recommended adjustments — typically either diluting hard water with distilled water or adding mineral concentrates to very soft water. For most home brewers, using a filtered water source near 75-150 ppm TDS produces excellent results without complex mineral additions.

About

The Water Calculator applies the SCA's Water Quality Handbook standards to help you understand and optimize the most abundant ingredient in your cup. Water's mineral composition is not neutral — it actively participates in the extraction chemistry that determines which flavor compounds dissolve from your grounds into solution and how they are perceived. Getting water right is often the highest-leverage improvement available to home brewers working with quality beans and a good grinder.

The key minerals in brewing water each play specific roles. Magnesium ions are particularly effective at facilitating extraction of coffee's aromatic compounds and enhancing brightness and clarity. Calcium ions support body and sweetness perception. Bicarbonate alkalinity buffers the brew's pH and is the primary cause of flat, muted flavor in hard water areas — it neutralizes coffee's natural organic acids that carry fruit and brightness. Sodium at low levels can enhance perceived sweetness. Understanding these roles helps you diagnose water-related flavor problems that improved beans or brewing technique cannot fix.

For most home brewers, the practical solution is straightforward: use a good carbon filter to eliminate chlorine and chloramines, and check that your filtered water TDS falls between 75 and 200 ppm. This alone eliminates the most common water-related flavor problems. Enthusiasts wanting to go further can explore Third Wave Water mineral concentrates or build water from scratch using distilled water plus measured mineral additions — an approach used by competition baristas worldwide who need to replicate exact water chemistry regardless of location.

FAQ

Why does water quality matter for coffee flavor?
Water makes up 98-99% of your brewed coffee, making it by far the most dominant ingredient in the cup. Its mineral composition directly affects extraction chemistry — minerals provide the ionic strength needed to dissolve coffee's flavor compounds from the grounds into solution. Calcium and magnesium ions are particularly important: they act as bridges between coffee's soluble aromatics and the water molecules carrying them, improving extraction of desirable compounds. Bicarbonate (alkalinity) buffers pH and significantly affects perceived acidity — high bicarbonate water neutralizes coffee's natural acids, flattening flavor and reducing brightness. The SCA Water Quality Handbook defines specific targets for each parameter based on their extraction effects.
What does the SCA recommend for brewing water?
The SCA's water quality standard for brewing recommends: total dissolved solids (TDS) of 150 ppm as a target (acceptable range 75-250 ppm); total hardness of 68 ppm CaCO3 as a target (acceptable range 17-85 ppm); calcium hardness of 51-68 ppm; bicarbonate alkalinity of 40 ppm as a target; sodium below 10 ppm; chlorine and chloramine at zero; pH between 6.5 and 7.5. These parameters represent decades of sensory panel research identifying the mineral levels that best facilitate complete, balanced extraction. Very soft water (under 50 ppm TDS) extracts unevenly, often producing flat or hollow flavors. Very hard water extracts poorly and tastes chalky.
Does chlorine in tap water affect coffee flavor?
Yes — chlorine and chloramines added to municipal water for disinfection react with coffee's aromatic compounds, producing chlorophenols and other off-flavor compounds that taste medicinal, antiseptic, or plastic-like. Even at low concentrations (standard municipal levels are 0.2-4 ppm), chlorine causes detectable flavor degradation in brewed coffee. Chlorine off-gasses relatively quickly — leaving tap water standing for 30 minutes in an uncovered container removes most free chlorine. Chloramine (increasingly common in municipal treatment) does not off-gas easily and requires a carbon filter to remove. A basic carbon filter (Brita or similar) is the minimum water treatment recommended for coffee brewing, as it removes chlorine, chloramine, and some heavy metals without removing beneficial minerals.
Is distilled water good for brewing coffee?
No — distilled water (zero TDS, zero minerals) produces poor coffee. Without dissolved minerals, water lacks the ionic strength to effectively extract coffee's soluble flavor compounds. Distilled water extracts selectively and incompletely, often producing hollow, flat brews with under-extracted characteristics despite normal extraction time. The SCA's water standard explicitly requires a minimum TDS of 75 ppm for this reason. However, distilled water is useful as a starting material for building custom brewing water — you add precise amounts of magnesium sulfate, calcium chloride, and baking soda in measured quantities to achieve target mineral profiles. This approach is popular among advanced home brewers who want the control of building water from scratch.
What is Rao/Maxwell or Third Wave Water approach to water preparation?
Several coffee professionals and researchers have developed recipes for building ideal brewing water from scratch using mineral salts added to distilled or reverse osmosis (RO) water. The approach popularized by companies like Third Wave Water uses a concentrate of food-grade calcium chloride, magnesium sulfate (Epsom salt), and baking soda in specific ratios, dissolved in distilled water to hit the SCA target parameters precisely. The advantage is perfect repeatability regardless of source water — you know exactly what mineral composition you are brewing with. Advanced formulas separate calcium from magnesium to tune for sweetness vs. acidity: magnesium tends to enhance brightness and acidity perception; calcium tends to enhance body and sweetness. The 'Rao/Maxwell Brewing Water' formula, published by Scott Rao, specifically optimizes the magnesium-to-calcium ratio for specialty filter coffee applications.