I learned that water matters by carrying an AeroPress Go almost everywhere.
Since 2022, I have brewed coffee in Brooklyn, Manhattan, Queens, Delhi, Agra, Jaipur, Vijayawada, and hotel rooms across India. I was usually carrying the same brewer and grinder. The coffee changed, of course, but so did the water. After enough trips, I could no longer pretend that water was merely the invisible part of the recipe.
The practical lesson is not that every beginner needs mineral sachets and a chemistry course. It is simpler: if the water tastes wrong, the coffee can taste wrong too. If you are uncertain, compare it against another safe drinking water before buying more coffee equipment.
Water advice changes when you brew in India
A lot of coffee advice online begins with a Western assumption: tap water is already considered drinking water, and the question is whether to soften, filter, or remineralise it for better coffee.
That is not the assumption in most Indian homes I know.
My family installed a water filter in Delhi in the late 1990s after my sister became ill. Since then, a purifier has simply been part of the kitchen. Friends and relatives use RO systems, UV purifiers, other household filters, or packaged water. We generally do not begin by asking whether tap water is ideal for coffee. We begin by asking whether it is safe and pleasant to drink at all.
This distinction matters. Coffee optimisation comes after drinking-water safety. A TDS meter, a pleasant taste, or a successful brew cannot establish that water is microbiologically or chemically safe. Use water already considered safe to drink and follow local public-health guidance.
When I moved to New York, drinking directly from the tap was normal. I lived in an old Brooklyn building and did not feel comfortable relying on the building's plumbing, so I installed a filter. My roommate initially thought it was unnecessary. When we eventually changed the visibly used filter, he was glad it had been there. That appearance was not a laboratory water test, but the experience made both of us more conscious of what sat between the municipal supply and our glasses.
What I tasted in Brooklyn, Manhattan, and Delhi
The filtered water in my Brooklyn flat made acceptable coffee, but I remember it tasting somewhat harsher. At my design studio in Manhattan, the filtered water produced coffee that seemed sweeter to me. I was not running a controlled experiment then, so I cannot tell you which mineral caused what. I can only say that the same brewing habits did not produce exactly the same cup everywhere.
The clearest example happened more recently in Delhi. Our home purifier stopped working properly. The drinking water began tasting strange, and my coffee changed with it. I bought a 10-litre container of Bisleri for brewing, repeated my normal routine, and the coffee immediately tasted like itself again.
That experience settled the beginner question for me. Before buying a new grinder or blaming a bag of coffee, make sure the water has not changed.
Season, source, building plumbing, and purifier maintenance can all alter the water arriving at an Indian coffee station. A recipe that worked last month can taste different after a supply change or a neglected filter. If several familiar coffees suddenly become unpleasant at once, water deserves a place on the troubleshooting list alongside freshness, grind, ratio, and water temperature.
What TDS tells you, and what it does not
At home, our untreated supply has measured roughly 190–200 parts per million on a basic TDS meter, while the purified water has sometimes measured around 15–20 ppm. A purifier technician suggested adding some minerals back. Those are readings from one household and one consumer meter, not targets I recommend for everybody.
TDS means total dissolved solids. The World Health Organization's fact sheet explains that this total can include calcium, magnesium, sodium, potassium, bicarbonates, chlorides, and sulphates. WHO does not set a health-based guideline value for TDS alone, although very high or very low concentrations can affect how acceptable water tastes.
The important phrase is “total.” A small conductivity-based TDS meter estimates how much dissolved material is present. It does not tell you exactly what that material is. It does not separately report hardness and alkalinity, identify chlorine, or prove that the water is safe.
Two waters can therefore show a similar TDS number and behave differently in coffee because their dissolved minerals are different. TDS is useful for noticing that your purifier output has changed or for comparing broad differences between water sources. It is not a coffee recipe.
Why the minerals still matter
Water is not flavourless in daily life. Dissolved minerals influence what drinking water tastes like, and they can change how acidity, sweetness, bitterness, and texture are perceived in coffee.
Two broad ideas are useful without turning the kitchen into a laboratory:
- General hardness is associated mainly with dissolved calcium and magnesium.
- Alkalinity describes the water's ability to resist changes in acidity and is often strongly influenced by bicarbonate.
High alkalinity can mute some of the lively acidity people seek in a light, fruit-forward coffee. Hardness and mineral composition can also alter the sensory result, while excessive scale-forming minerals matter to kettles and espresso machines.
The chemistry is still more nuanced than many confident internet recipes suggest. A widely discussed 2014 paper on dissolved cations and coffee modelled how ions including magnesium and calcium could interact with coffee compounds. More recent coffee research and debate continue to examine whether minerals primarily change extraction itself, perception in the finished drink, or both. For a home brewer, the honest conclusion is not “magnesium always makes coffee fruitier.” It is that mineral identity and alkalinity matter, while one TDS number cannot explain the cup.
This is also why I would not convert someone else's mineral preference into a universal recommendation. The Coffee Chronicler's five coffee-water mistakes and Lance Hedrick's water chemistry deep dive both make a useful point: different roast styles, brewing methods, and palates may benefit from different water. Their detailed recipes are for people who want to pursue the subject further, not prerequisites for making good coffee at home.
Can very low-TDS RO water make coffee taste flat?
It can produce a cup that tastes flat, sharp, or otherwise different, but I would not diagnose a coffee from the TDS number alone.
Our low-reading filtered water usually makes coffee I enjoy. Bisleri has also worked well for me. I have not felt compelled to remineralise every brew, and I cannot honestly claim that a particular ppm target would improve it. Another household with a different purifier, source water, and coffee might reach a different conclusion.
If your coffee consistently tastes empty despite fresh beans and a sensible recipe, comparing the RO water with another safe drinking water is worthwhile. If the second cup is clearly better across repeated comparisons, then you have evidence that water treatment or remineralisation may be useful. If both cups taste equally good, do not invent a problem because a video told you one should exist.
Pour-over and espresso do not create the same water problem
I notice water differences more easily in pour-over than in espresso. A V60 or AeroPress-style black coffee is comparatively dilute and exposed; there is nowhere for an unusual water taste to hide. Espresso is concentrated, and I often drink it with milk, so differences have been less obvious to me.
That is my sensory experience, not a rule that espresso is less affected by water.
Espresso adds an equipment problem. Water repeatedly heated inside a machine can cause scale or, at the other extreme, contribute to corrosion depending on its chemistry and the machine. The Specialty Coffee Association's discussion of water, acidity, and different extraction methods distinguishes sensory goals from the practical requirements of filter and espresso systems.
Do not pour distilled or improvised DIY water into an expensive espresso machine merely because a recipe worked for somebody online. Follow the manufacturer's water guidance, understand the warranty implications, and consider qualified service advice. My home espresso guide covers the rest of the workflow without pretending water is the only variable.
Do beginners need mineral sachets?
Usually, no.
If your safe filtered water tastes clean and your coffee tastes good, keep brewing. Learn to control dose, ratio, grind, time, and temperature first. Grinding fresh will usually teach a beginner more than copying an advanced mineral recipe without understanding it.
Consider going deeper when:
- several familiar coffees taste consistently dull, harsh, or strangely sour;
- your coffee tastes substantially better at a cafe even after you reproduce its recipe;
- your purifier strips the water heavily and repeated comparisons favour another water;
- scale is accumulating quickly in a kettle or espresso machine;
- you enjoy controlled tasting and genuinely want water chemistry to become part of the hobby.
Even then, start with evidence. Try a packaged water, obtain a reliable water report, test hardness and alkalinity rather than TDS alone, or ask the roaster what water they used. Do not begin by buying five mineral concentrates.
A two-water test worth doing
This is the simplest useful water experiment I know.
- Choose one familiar coffee and one repeatable recipe.
- Use your normal safe filtered drinking water for cup A.
- Use a different safe packaged or filtered drinking water for cup B.
- Keep coffee dose, grind, water quantity, temperature, brewer, pouring, and brew time as similar as possible.
- Let both cups cool to the same comfortable temperature.
- Taste them side by side without trying to guess specific flavour notes.
Ask simpler questions:
- Is one cup sweeter?
- Is one brighter or more muted?
- Does either taste metallic, salty, chalky, harsh, or hollow?
- Which would I rather finish?
The comparison matters more than whether Bisleri, Aquafina, or your household purifier wins. Packaged-water composition can also vary, and buying plastic bottles for every brew creates cost and waste. I use bottled water as a troubleshooting control or travel fallback, not as a universal coffee standard.
Record both brews in Brew Tracker if you want to repeat the test. Change only the water. Otherwise you will not know whether water, grind, or temperature produced the difference.
My practical recommendation for an Indian beginner
Use safe drinking water that tastes clean. Maintain the purifier you already have. If coffee suddenly changes, taste the water by itself and check whether the filter, supply, or season has changed.
If you still have doubts, buy one container of packaged drinking water and run a side-by-side brew. That is cheaper and more informative than immediately replacing a grinder or ordering coffee-water minerals.
If there is no meaningful difference, continue with the water you have. If the bottled-water cup repeatedly wins, investigate your purifier and local water before attempting remineralisation. If an espresso machine is involved, follow its water requirements rather than improvising.
Water can make or break coffee, but it does not need to become another form of equipment anxiety. Judge the water available where you live, compare it honestly, and stop adjusting when the cup tastes good.