Why Does Water Change the Taste of Tea? A Practical Guide to Better Brewing Water

There is a particular kind of disappointing tea session that took me a while to understand.

The leaves are familiar. The gaiwan is familiar. I use the same amount of tea, the same temperature and roughly the same timings. Yet the cup feels muted. The aroma seems smaller. A sweetness I remember clearly has almost disappeared.

My first instinct used to be to change the brewing.

Quite often, the real difference was the water.

Water is easy to overlook because it looks neutral. In the cup, it is anything but. Its mineral content, hardness, alkalinity and treatment can change how tea extracts and how we perceive aroma, texture, brightness and astringency.

I do not think this needs to become another part of tea that requires laboratory equipment. But if a tea tastes inexplicably different from one place to another, water is one of the first things I now consider.

Why water matters so much

Brewing tea is an extraction. Hot water moves soluble compounds from the leaf into the liquor, and the composition of that water influences the process.

Calcium and magnesium are the minerals most commonly associated with water hardness. Bicarbonate contributes to alkalinity. Chlorine or chloramine may also be present in treated mains water. None of these automatically makes water unsafe or unpleasant to drink, but their concentration can alter what happens when that water meets tea.

Very hard, alkaline water can make delicate teas seem flatter or less aromatic and can contribute to a film on the surface of the liquor. At the other extreme, heavily purified or distilled water can produce a cup that feels thin or oddly empty.

The useful answer, as with so much in tea, tends to be somewhere in the middle.

Hard water is not simply “bad water”

I am wary of telling anyone that their tap water is wrong.

Hard water is simply water containing a relatively high concentration of dissolved calcium and magnesium. Across much of southern and eastern England, that is completely normal.

For everyday drinking, you may be perfectly happy with it. Tea, however, can make the differences more obvious, particularly when I am brewing something aromatic and relatively subtle.

With harder water I often notice the cup becoming less transparent in character. Florals can feel quieter. High notes are harder to separate. Sometimes the tea seems heavier without actually having more satisfying body.

That does not mean every robust tea suddenly becomes undrinkable. It means the water has become another brewing variable.

Can water be too soft?

Yes, and this is where the simple advice to “use the purest water possible” becomes unhelpful.

Distilled water and very heavily purified reverse-osmosis water contain almost no dissolved minerals. They may sound ideal because there is nothing to interfere with the tea, but in practice the resulting cup can feel thin, hollow or strangely sharp.

A modest amount of mineral content can help give a brew structure and a more satisfying mouthfeel.

I therefore do not chase zero on a TDS meter. If I use reverse-osmosis water, I prefer it remineralised rather than completely stripped.

What does TDS actually tell you?

TDS means total dissolved solids. A small handheld meter estimates the overall concentration of dissolved material in water, usually expressed in parts per million or milligrams per litre.

It is useful, but limited.

A reading of 100 ppm does not tell you whether those dissolved solids are mostly calcium, magnesium, bicarbonate, sodium or something else. Two waters with the same TDS can therefore brew tea differently.

As a broad starting point, moderately soft water with relatively low mineralisation is often easier to brew fine tea with than very hard water. Current tea-water guides commonly suggest somewhere around 50–150 mg/L TDS as a practical range rather than a universal target.

I treat that number as orientation, not a recipe.

Filtered tap water is often the easiest improvement

Before buying specialist water or trying to build a mineral profile from salts, I would start with the simplest experiment available.

Brew the same tea with your normal tap water and with filtered water.

A carbon-based filter can reduce chlorine-related tastes and odours, while some domestic filter systems also reduce part of the hardness. The precise effect depends on the filter and on the water entering it.

If the filtered cup is clearer, sweeter or more aromatic to you, you have learnt something useful about your own water without turning tea into chemistry homework.

If there is almost no difference, that is useful too.

The tea I use to test water

When I want to compare water, I choose a tea I already know rather than an unfamiliar one.

An aromatic oolong is particularly revealing for me because I can pay attention to fragrance, texture and the finish across several infusions. Our 2025 Taiwanese Milk Oolong is one tea I can use for this sort of comparison because I know what I expect from its texture and naturally creamy character.

The point is not that this particular tea requires one special water. The point is familiarity. If I know the tea, changes caused by the water are easier to recognise.

A simple three-water experiment

If you are curious, try this once. You do not need to repeat it every time you make tea.

Prepare three waters:

• your normal tap water;
• filtered tap water;
• a still, relatively low-mineral spring water.

Use the same tea, the same leaf-to-water ratio, the same vessels and the same brewing temperature. I would keep the infusions short enough that bitterness does not dominate the comparison.

Then ignore the labels for a moment and taste.

Which cup smells most clearly? Which has the best texture? Where is the sweetness easiest to notice? Does one finish more cleanly? Does one feel oddly thin or heavy?

I find this much more useful than trying to decide intellectually which water ought to win.

Do different teas prefer different water?

They can respond differently.

Delicate green and white teas often expose hard or strongly alkaline water quickly because subtle aromas and brightness are easily muted. Highly aromatic oolongs can also make water differences obvious.

More robust red teas, Shu Pu’er and some darker teas may be more forgiving, although that does not mean water stops mattering.

I would resist creating a separate numerical water recipe for every tea unless that kind of experimentation genuinely interests you. For everyday brewing, finding one moderately soft, clean-tasting water that works well across your collection is far more useful.

What about bottled water?

Bottled water is not automatically better.

Some mineral waters are extremely mineral-rich and can be worse for delicate tea than your tap water. If I buy water specifically for brewing, I look for a still water with relatively modest mineralisation rather than assuming that “mineral water” means suitable tea water.

I also prefer filtration where practical because it avoids turning a daily tea habit into a pile of plastic bottles.

And the kettle?

If you live in a hard-water area, limescale in the kettle is another clue that minerals are present in substantial amounts.

Descaling the kettle is sensible maintenance, but it does not magically turn the water you subsequently add into soft water. The scale is evidence of the water chemistry, not the cause of it.

I keep the kettle clean because I want as few unwanted flavours in the session as possible.

Change the water before blaming the tea

This is probably the most useful lesson water has taught me.

If a tea I know suddenly seems dull, I do not immediately add more leaf, raise the temperature or stretch the infusion. Those changes can easily push a tea harder while leaving the underlying problem untouched.

I ask what changed.

Sometimes it is the tea. Sometimes it is me. Sometimes it is the water.

A good tea session does not need perfectly engineered water. It needs water that gets out of the way enough for the leaf to speak clearly.

Once I found water that worked reliably for the teas I drink, I mostly stopped thinking about it.

Which, in a way, is exactly what I want from water.