MINERALS AND COFFEE
Why Water Makes or Breaks Your Filter Coffee — And What to Do About It
You bought good coffee. You dialled in your grind. You nailed your pour. And somehow the cup still doesn't taste the way it should.
Nine times out of ten, the answer is water.
Coffee is 98% water. Which means the water you use isn't just a vehicle for your coffee — it is your coffee. The minerals dissolved in it interact with every compound in the bean, determining what gets extracted, what gets left behind, and ultimately what ends up on your palate.
Most people never think about this. The ones who do make noticeably better coffee.
Here's everything you need to know.
WHY TAP WATER IS OFTEN THE PROBLEM
Adelaide tap water is heavily chlorinated and often high in sodium — neither of which are friends to specialty coffee. Chlorine suppresses delicate aromatics and can give your cup a flat, slightly chemical quality. High sodium dulls sweetness and mutes the kind of nuanced flavour notes you're paying for in a quality single origin.
This doesn't mean tap water is unusable — but it does mean that if you're brewing a $30 bag of specialty coffee with straight tap water, you're leaving a lot in the filter.
The simplest upgrade is filtered water. A basic carbon filter jug removes chlorine and most of the off-flavours immediately. For most home brewers, this alone makes a meaningful difference.
But if you want to go deeper — and understand why your coffee tastes the way it does — you need to understand minerals.
THE MINERALS THAT MATTER
Water isn't just H₂O. Depending on its source, it contains varying levels of dissolved minerals, each of which interacts differently with coffee.
Magnesium (Mg²⁺) Magnesium is the most important mineral for filter coffee extraction. It has a strong affinity for the aromatic compounds and organic acids that give specialty coffee its character — florals, fruit notes, brightness. Higher magnesium levels produce more vibrant, expressive cups. This is why magnesium bicarbonate is the foundation of most specialty coffee water recipes.
Calcium (Ca²⁺) Calcium contributes body and mouthfeel. Where magnesium lifts and brightens, calcium rounds and fills. Too much calcium can make a cup feel heavy or chalky, but the right amount adds a satisfying weight that balances brightness beautifully.
Bicarbonates (HCO₃⁻) Bicarbonates act as a buffer — they neutralise acidity in the cup. A small amount of bicarbonate smooths harsh edges and adds sweetness. Too much and you start suppressing the very acidity that makes a bright, clean filter coffee so exciting. For delicate coffees like our Yellow Gesha or Wush Wush, keeping bicarbonate levels low lets the natural fruit and floral notes speak clearly.
Sodium (Na⁺) A very small amount of sodium enhances sweetness — but sodium is the mineral most likely to already be present in excess in your tap water. Too much sodium suppresses florals and creates a flat, one-dimensional cup. For coffees with delicate aromatics, keep sodium to an absolute minimum.
Sulfates (SO₄²⁻) Sulfates sharpen acidity and add definition to flavour. Useful in small amounts for coffees where you want bright, crisp acidity — but too much can make a cup feel dry or astringent.
WHAT IS TDS AND WHY DOES IT MATTER
TDS stands for Total Dissolved Solids — it measures the total concentration of all minerals in your water, expressed in parts per million (ppm) or milligrams per litre (mg/L).
The Specialty Coffee Association recommends a target TDS of 75–150 ppm for brewing water, with 150 ppm as a practical sweet spot for most filter coffee.
Water that's too low in TDS (below 50 ppm) — like distilled or heavily filtered water — is actually too pure. It extracts aggressively and unevenly, producing hollow, harsh cups. Water that's too high (above 250 ppm) over-buffers the coffee and produces flat, muted results.
You can measure your water's TDS with a simple TDS meter — they cost around $15–20 online and give you an instant reading.
BUILDING YOUR OWN BREW WATER
If you want full control, you can build your own water from scratch using mineral concentrates added to distilled or reverse-osmosis water. This sounds complicated but is actually very straightforward.
The simplest starting point is Lotus Water — a concentrate system that lets you add precise amounts of magnesium bicarbonate, calcium chloride and potassium bicarbonate to a base of distilled water. Target:
TDS: 80–150 ppm
Magnesium: 20–30 mg/L — your primary extraction mineral
Calcium: 40–70 mg/L — body and mouthfeel
Bicarbonate (KH): 40–60 mg/L — buffer without suppressing acidity
Sodium: as low as possible — under 10 mg/L
For our Ombligon Floral Symphony and Yellow Gesha, we lean toward the lower end of bicarbonate to keep the florals lifted and unmasked. For fuller-bodied coffees like our Guji Boku, a little more calcium adds to the natural richness.
THE SIMPLE VERSION
If building your own water sounds like too much, here's the practical shortcut most specialty coffee lovers use:
Volvic still mineral water is one of the best off-the-shelf options for filter coffee. Its mineral profile sits very close to ideal brewing water — low sodium, moderate magnesium, clean and balanced. You can find it at most supermarkets.
Alternatively, BRITA filtered tap water removes the worst offenders (chlorine, excess sodium) and gets you most of the way there without any extra steps.
THE TAKEAWAY
Great coffee starts long before the grind. The water you choose either unlocks what's in the bean or gets in its way.
Start with filtered water. Get a TDS meter if you're curious. And if you really want to taste what your coffee is capable of — try building your brew water once. The difference will surprise you.
At Auro we taste every coffee with water dialled specifically for that bean. It's one of the reasons our market customers tell us our coffee tastes different at home — and now you know exactly how to fix that.
Coffee is joy, mindful and a love language.
— Krish & Prathima, Auro Speciality Coffee
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