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What Are the SCA Water Standards?
The Specialty Coffee Association tested what water makes the best coffee and defined specific mineral ranges. Too few minerals and your water can't pull enough flavor from the grounds. Too many and it over-extracts, bringing bitterness and chalkiness into your cup. The SCA standards are the sweet spot in between.
| Parameter | SCA Range | Target | What It Does to Your Cup |
|---|---|---|---|
| GH | 17–85 ppm CaCO₃ | 68 | Pulls flavor from the grounds. Too low → thin, sour coffee. Too high → bitter, chalky. |
| KH | 30–50 ppm CaCO₃ | 40 | Controls acidity. Too low → sharp, sour. Too high → flat, dull. |
| Sodium | 0–10 mg/L | 0 | Above 10 mg/L you start tasting salt or metal. |
| pH | 6.5–7.5 | 7.0 | Shifts how bright or mellow your coffee tastes. |
| TDS | 75–250 ppm | 150 | Total minerals in the water. Low = weak extraction. High = harsh cup. |
Why Does Water Matter for Coffee?
Your coffee is 98% water. The minerals in that water are what actually pull flavor out of the grounds — without them, you get a weak, sour cup no matter how good the beans are. With too many, you get bitterness and chalk. The SCA tested this extensively and found the range where extraction is balanced and coffee tastes its best.
Calcium and magnesium (measured as Hardness, or GH) do the heavy lifting — they grab onto flavor compounds during brewing and carry them into your cup. Alkalinity (KH) controls the acidity: it's what makes the difference between a bright, juicy cup and a flat, dull one. Sodium is fine in small amounts, but above 10 mg/L it adds a salty or metallic edge.
You can have a $25 single-origin and a dialed-in recipe, and it'll still taste off if the water is wrong. Fixing your water is one of the biggest improvements you can make — often more impactful than upgrading your grinder.
How to Fix Your Water
The approach is straightforward: start with distilled or reverse-osmosis (RO) water as a clean base, then add small amounts of minerals to hit the SCA targets. You only need three compounds, all available at a grocery store or online.
| What to Add | You Know It As | How It Works |
|---|---|---|
| NaHCO₃ | Baking soda | Raises alkalinity. Keeps your coffee from tasting too sharp or sour. |
| CaCl₂ | Calcium chloride | Adds calcium for better extraction. Brings body and sweetness to the cup. |
| MgSO₄ | Epsom salt | Adds magnesium for extraction. Works alongside calcium for a balanced cup. |
A precision kitchen scale makes this easy. Most people prepare a concentrated solution — dissolve the minerals in 1 liter of distilled water, then add a measured amount to each brew. Once you have the recipe dialed in, it takes seconds.
Frequently Asked Questions
Where do I find my water's mineral data?
Bottled water lists it right on the label. For tap water, check your local utility's annual water quality report — most are online. You can also pick up a home test kit for more precise readings. You're looking for calcium, magnesium, bicarbonate, sodium, and TDS.
Can I use tap water for specialty coffee?
Sometimes. Some tap water is naturally within SCA range — test yours first. If it's close, a small tweak is all you need. If it's very hard or very soft, it's easier to start with filtered or RO water and build from there.
What's the difference between GH and KH?
GH (General Hardness) is calcium and magnesium — the minerals that pull flavor out of your coffee. KH (Alkalinity) is bicarbonates — they control how acidic or flat your cup tastes. Both matter, but they affect your coffee in different ways.
Do I need to adjust my water for espresso too?
Even more so. Espresso amplifies everything — higher pressure, higher concentration. Bad water makes harsh or flat shots, and hard water scales your machine over time. The same SCA ranges apply.
How often should I test my water?
Tap water: every few months, since mineral content shifts with the seasons. Bottled water: once is enough — the composition stays consistent. Building your own water from RO? The recipe is your test.
Last updated: 2026-04-13