TDS in water: what it is and why it matters

Anyone who has held a bottle of premium water and read the label carefully has encountered three letters that recur across the segment: TDS, followed by a number in milligrams per liter. The figure appears on Norwegian waters that cost USD 60 per bottle, on Italian waters that accompany tasting menus in Milan, on lists of fine waters served in ultra-premium hotels in the Emirates. But rarely does anyone explain what it means.

This piece is a reference on TDS, written for those who want to understand the concept without going through a technical course. The number itself is simple. What it reveals — about the water and about its origin — is not.

What TDS measures

TDS stands for total dissolved solids. It measures, in milligrams per liter, the concentration of everything dissolved in the water as minerals and salts: calcium, magnesium, sodium, potassium, bicarbonates, sulfates, chlorides, and trace elements.

The measurement is international. Laboratories in any country test TDS by the same method and produce comparable results. When a label declares TDS of 8 mg/L, that number means exactly the same thing in São Paulo, Tokyo, or Oslo.

Distilled water has zero TDS — nothing is dissolved in it. Seawater sits around 35,000 mg/L. Everything anyone drinks falls somewhere between those two extremes. But the genuinely relevant range for bottled drinking water runs from about 5 mg/L (rare waters of atmospheric or glacial origin) to about 2,500 mg/L (mineral waters of extreme mineralization).

Where common waters sit

For reference, some real numbers.

Most Brazilian mineral waters sold in supermarkets sit between 50 and 200 mg/L. São Lourenço, Minalba, Crystal, Bonafont — all in that range. It is the territory the Brazilian consumer knows without knowing.

Italian Acqua Panna sits around 140 mg/L. French Evian, around 357 mg/L. Fiji, from the Pacific, around 210 mg/L. Norwegian Voss, around 22 mg/L. Italian San Pellegrino, sparkling, exceeds 1,100 mg/L.

And at the opposite end, atmospheric waters captured from air humidity before any contact with soil register TDS between 5 and 12 mg/L. AWA, captured from the Amazon rainforest, sits at 6 mg/L. Svalbarði, from Norway, at 8.

These numbers tell distinct geological stories. Water that spends years passing through rock comes out mineralized. Water that never touched soil comes out almost mineral-free.

The international scale

The Fine Water Society, the segment's international authority, classifies waters into five categories by TDS. The scale is the reference for water menus in fine dining around the world.

Super Low sits below 50 mg/L. Waters in this range have neutral flavor, imperceptible mineral weight, the function of absolute purity. AWA and Svalbarði belong here. Voss as well. These are waters for accompanying delicate dishes or for harmonizing with wines and spirits where mineral interference would intrude.

Low sits between 50 and 250 mg/L. Mineralization is perceptible but soft. It covers most popular premium waters. Fiji, Acqua Panna, Brazilian brands like Prata and Lindoia.

Medium sits between 250 and 800 mg/L. Clear mineral flavor. Evian, Perrier. They work with denser dishes, aged cheeses, red meat.

High sits between 800 and 1,500 mg/L. Pronounced mineral flavor. San Pellegrino is the reference. It accompanies full-bodied dishes, red wines, blue cheeses.

Very High exceeds 1,500 mg/L. A niche category. Intense, almost medicinal mineral flavor. German and French waters like Gerolsteiner and Contrex. Limited consumption frequency, clear digestive role.

Each category has a function. TDS does not classify good versus bad — it classifies by terrain of use.

Why TDS matters on the palate

Mineral in water has weight. Weight in the mouth, weight on the palate, weight on the perception of what comes next.

Drinking Super Low TDS water is a cleaner experience than most people know. No mineral weight, no residual taste, no interference. Certified water sommeliers describe this quality as absence. Not absence in the sense of emptiness — absence in the sense of non-interference. The palate stays neutral, ready for the next flavor.

Water with medium or high TDS, by contrast, leaves a mark. There is a mineral residual that shifts the perception of the dish, the wine, the coffee that follows. In an everyday meal, this does not matter. In a tasting menu where each course is built on a specific sensory balance, it matters a great deal.

The practical rule international sommeliers use: the TDS of the water should be comparable to or lower than the profile of the dish and the wine. Delicate dishes call for low TDS. Dense dishes tolerate medium TDS. Never the reverse — high-mineral water alongside raw fish or ceviche is operational interference.

Why TDS matters in pairing

In houses with a structured water menu, TDS works as the primary selection filter. The choice is not "still or sparkling" — it is between mineralization ranges.

Single malt whisky calls for Super Low water — any added mineral content blurs the spirit's nuances. Dry sparkling wine accepts Low or Medium. Full-bodied red wine pairs well with Medium. Specialty coffee, particularly subtle varieties like Geisha, calls for Super Low before and after to clear the palate without altering the coffee's perception.

The logic is no different from wine-and-food pairing — it is the same logic, applied to the mineral content of the water.

High TDS isn't bad, low TDS isn't good

This is the most common misconception about TDS. The number does not classify quality. It classifies terrain of use.

Water with high TDS carries minerals. Calcium, magnesium, bicarbonate in quantities that effectively contribute to daily mineral intake. For those who appreciate mineral weight, it is the preferred water. For certain dishes, it is the right water.

Water with low TDS does not carry minerals. This is not a negative — it simply means mineralization needs to come from another source in the diet. People who eat varied diets typically get sufficient minerals from food. For those who seek palate purity, Super Low water is the reference.

Each range has its audience, its function, its context. The right question is never "which TDS is best." It is "what am I going to use it for."

When TDS tells the story of origin

This is where the technical number becomes narrative.

Waters with very high TDS typically come from deep aquifers in mineral-rich terrain — basaltic, calcareous, volcanic formations. The water travels through that rock for decades or centuries before being captured. The TDS tells that journey.

Waters with medium TDS come from surface sources or shallow aquifers in less mineralized terrain. Most Brazilian table waters.

Waters with low TDS (Low, in the 50 to 250 mg/L range) typically come from sources in geologically neutral terrain — granite, quartz, regions with poorly mineralized soils.

And waters with Super Low TDS tell a specific story: little contact with rock, or none. Glacial waters from recent melt. Atmospheric waters captured from air before touching soil. Waters from sources in extremely neutral terrain, rare.

AWA, captured from humidity released by the Amazon rainforest, has TDS of 6 mg/L for the same structural reason that Svalbarði has 8: complete absence of contact with soil during the formation of the water. The number confirms the origin.

Final notes

Knowing the TDS of the water you drink is a small gesture of gastronomic literacy. It does not change everyday drinking — filtered tap water still solves hydration. But it changes the relationship with fine waters, with premium hospitality menus, with the category as a whole.

Those who understand TDS read any bottled water label better. They identify in seconds whether the water on the table is Super Low, Medium, or High. They assess coherence between declared origin and technical data. They notice when a brand communicates origin without communicating TDS — and what that may mean.

The number is simple. The reading, after some time, becomes reflex.