What the SCA Standard Covers
The Specialty Coffee Association publishes water quality standards as part of its broader brewing standards. These guidelines define the chemical characteristics of water that produce the best extraction results and the most balanced flavor when brewing coffee. The standard is not law — it is a consensus recommendation developed by coffee scientists and industry professionals based on decades of sensory evaluation and extraction research.
The SCA water standard exists because water quality is the single largest variable in coffee brewing that most people never think about. Two cups brewed with identical coffee, identical grind, identical ratio, and identical technique will taste completely different if one uses soft mountain spring water and the other uses hard municipal water loaded with chlorine and bicarbonate. The standard gives roasters, cafes, competition baristas, and home brewers a shared reference point.
The SCA Target Values
The SCA water quality standard specifies the following parameters:
Total Dissolved Solids (TDS)
- Target: 150 mg/L (ppm)
- Acceptable range: 75-250 mg/L
- TDS measures the total concentration of all dissolved minerals, salts, and organic matter in water. It is measured with an inexpensive conductivity meter often sold as a “TDS meter.” Water at the low end of the range (75 ppm) will extract differently than water at the high end (250 ppm), so the target of 150 ppm represents the sweet spot where extraction efficiency is high but not excessive.
Calcium Hardness
- Target: 68 mg/L as CaCO3 (approximately 4 grains)
- Acceptable range: 17-85 mg/L as CaCO3 (1-5 grains)
- Calcium hardness measures the concentration of calcium and, by some definitions, magnesium dissolved in the water. These divalent cations are the primary extraction agents — they bond with flavor compounds in coffee and carry them into solution. Too little hardness means weak extraction. Too much means aggressive extraction and potential scale buildup in equipment.
Total Alkalinity
- Target: 40 mg/L as CaCO3
- Acceptable range: at or near 40 mg/L
- Alkalinity measures the buffering capacity of water — its ability to resist changes in pH when acids are added. In coffee brewing, organic acids from the coffee itself lower the pH of the brew. Adequate alkalinity prevents the brew from becoming excessively acidic and sour. However, excessive alkalinity neutralizes too much acidity, producing a flat, dull cup.
pH
- Target: 7.0
- Acceptable range: 6.5-7.5
- The pH of brewing water should be close to neutral. Water that is too acidic (below 6.5) can produce metallic or sour flavors even before it contacts coffee. Water that is too alkaline (above 7.5) tends to flatten flavor.
Sodium
- Target: 10 mg/L
- Acceptable range: at or near 10 mg/L
- Small amounts of sodium can enhance sweetness perception, similar to how a pinch of salt improves food. Excess sodium introduces a salty or mineral taste. Municipal water with high sodium levels from water softening systems is a common problem.
Odor and Appearance
- Clean, fresh, odor-free
- No chlorine or chloramine taste or smell
- Clear with no visible particulates
- These are baseline requirements. Water that smells or tastes of chlorine, sulfur, or anything else will taint the coffee regardless of its mineral content.
How to Test Your Water
Testing your water against SCA standards requires different tools depending on how precise you want to be:
TDS meter ($10-20). This handheld device measures total dissolved solids by electrical conductivity. It gives you a single number in ppm. Dip it in your water, wait for the reading to stabilize, and compare to the 75-250 ppm range. TDS meters are accurate enough for practical purposes but cannot tell you the specific composition of those dissolved solids.
Test strips ($10-15 for a pack). Pool and aquarium test strips measure pH, total hardness, and sometimes alkalinity. They are less precise than laboratory methods but sufficient for identifying whether your water is in the right ballpark. Look for strips that test GH (general hardness), KH (carbonate hardness/alkalinity), and pH.
Drop test kits ($15-30). Aquarium drop test kits for GH and KH provide more accurate readings than strips. You add drops of reagent to a water sample and count how many drops it takes for a color change. Each drop represents a known increment of hardness or alkalinity.
Laboratory analysis ($20-50). Your municipal water utility publishes an annual water quality report (Consumer Confidence Report in the United States) that includes most of the parameters the SCA specifies. You can also send a sample to a water testing laboratory like Ward Laboratories for a comprehensive mineral analysis. This is the most accurate option and useful as a baseline measurement.
Refractometer (for TDS of brewed coffee). Note that a coffee refractometer measures the TDS of brewed coffee, not of the water itself. It is a different measurement used for calculating extraction yield. Do not confuse the two.
What the Numbers Mean in Practice
Understanding the standard requires connecting the numbers to what happens during extraction.
Low TDS water (below 75 ppm) is “hungry” water — it has significant capacity to dissolve compounds but may extract too aggressively, pulling undesirable flavors along with desirable ones. Distilled water (0 ppm) tastes flat and tends to produce harsh, astringent brews. However, very soft water with some mineral content (40-70 ppm) can produce extraordinarily clean and bright cups with certain light-roasted coffees.
High TDS water (above 250 ppm) is already carrying a heavy mineral load and has less capacity to dissolve coffee compounds. Extraction will be muted, and the water’s own mineral taste may interfere with coffee flavors. Extremely hard water also causes rapid scale buildup in kettles and espresso machines.
Water in the target range (around 150 ppm) balances extraction efficiency with flavor neutrality. The minerals present are enough to drive extraction but not so concentrated that they dominate the taste.
Alkalinity at 40 ppm provides just enough buffering to round off the sharpest edges of coffee acidity without flattening it. This is perhaps the most flavor-critical parameter. Alkalinity that is too high (above 80-100 ppm) will make every coffee taste dull and lifeless. Alkalinity that is too low (below 20 ppm) will let through all the organic acids unmodulated, which can be either brilliant or punishing depending on the coffee.
Chlorine and Chloramine
Municipal water treatment adds chlorine or chloramine to kill bacteria. Both are devastating to coffee flavor even at concentrations too low to consciously detect in plain water. Chlorine produces a sharp, chemical, swimming-pool taste. Chloramine is more subtle but creates a rubbery or medicinal off-note.
Chlorine is relatively easy to remove. It will dissipate if water is left in an open container for 24 hours. It is also removed effectively by activated carbon filters (Brita, Pur, refrigerator filters, and the carbon stages of under-sink systems).
Chloramine is more persistent. It does not evaporate and requires catalytic carbon or longer contact time with standard carbon filters to remove. Many municipalities have switched from chlorine to chloramine because it persists longer in the distribution system. Check your local water report to know which disinfectant your utility uses.
A simple carbon filter — even an inexpensive pitcher filter — addresses chlorine effectively and is the minimum recommendation for anyone brewing coffee with municipal tap water. If your utility uses chloramine, you may need a higher-quality carbon block filter or a dedicated chloramine reduction filter.
Limitations of the Standard
The SCA standard is a useful guideline, not a universal prescription. Several limitations are worth noting:
It treats hardness as a single number. The standard specifies calcium hardness but does not distinguish between calcium and magnesium, which behave differently during extraction. Research by Christopher Hendon and others has shown that magnesium extracts certain flavor compounds more effectively than calcium. The standard predates this more nuanced understanding.
It does not specify hardness-to-alkalinity ratio. The relationship between hardness and alkalinity matters as much as the absolute values. Water with 80 ppm hardness and 40 ppm alkalinity will brew very differently from water with 80 ppm hardness and 80 ppm alkalinity, even though both are within the acceptable range.
It is optimized for a middle ground. The standard works well for medium-roasted coffees but may not be ideal for every brewing scenario. Very light Nordic-style roasts often perform better with softer, lower-alkalinity water that preserves their delicate acidity. Very dark roasts may benefit from higher alkalinity to temper bitterness.
It does not account for brew method. Espresso, immersion, and percolation methods interact with water chemistry differently. The standard was primarily developed in the context of drip/percolation brewing.
Despite these limitations, the SCA water quality standard remains the most widely referenced baseline in specialty coffee. If your water falls within the recommended ranges and is free of chlorine and off-flavors, it will produce good coffee with most brewing methods and most coffees. From that baseline, you can refine further using custom water recipes if you want to optimize for a specific coffee, roast level, or brewing method.
Practical Steps for Compliance
For most home brewers, achieving SCA-compliant water follows one of two paths:
Path 1: Filter and test. If your municipal water is in the 100-200 ppm TDS range with moderate hardness and reasonable alkalinity, a carbon filter to remove chlorine/chloramine may be all you need. Test your filtered water with a TDS meter and test strips to confirm it falls within range.
Path 2: Build from scratch. If your tap water is far outside the recommended ranges — very hard, very soft, or very alkaline — building your own water from distilled or RO base with mineral concentrates is more reliable than trying to adjust problematic tap water. This approach guarantees compliance and consistency regardless of municipal water variability.
Competition baristas almost universally use custom-built water, both for consistency and for the ability to fine-tune mineral content to a specific coffee. For daily home brewing, either path works well. The important thing is knowing what is in your water and ensuring it is free of off-flavors.