What is TDS?
TDS stands for Total Dissolved Solids.
"Dissolved solids" are inorganic substances - minerals, salts, metals, cations (positively charged ions), anions (negatively charged ions) - dissolved in water.
The very highest TDS levels for mineral water are in the area of 3,000 milligrams per liter.
The lowest possible TDS is 0, the pure water compound of two hydrogen atoms bound to one oxygen atom. There is no is naturally occurring 0 TDS mineral water; 0 TDS water is "distilled water."
Milligrams per liter, abbreviated as "mg/l," is also synonymous with Parts Per Million, abbreviated as "ppm."
What are the different properties of High TDS and Low TDS mineral waters?
Higher TDS waters have a heavier taste and a much more prominent "mouthfeel," a term used by water connoisseurs to describe the overall sensory impression. The mouthfeel may include slight saltiness where there is an appreciable Sodium content in the water.
Lower TDS waters, particularly those with the very lowest TDS, have virtually no taste, and "express" an airy or light mouthfeel. Consumers describe the lowest TDS waters as tasting clean, with even a hint of sweetness.
Natural waters are like snowflakes - no two are exactly the same. Unlike processed waters that are de-bacterialized, homogenized, filtered, polished, and subjected to other procedures that ensure bottled products with 100% identical chemistry, natural waters are organic and behave like organic substances. Samplings over time of the same natural mineral water from the same point of effluence show small deviations in chemistry. This occurs because the water is "alive" and is affected by the geology, climate, and other environmental and terrestrial factors.
High TDS waters have a great variety of interesting chemistries. Some are heavy in Sodium, or Bicarbonate, or Chloride, or Sulphate. Others contain relatively high amounts of substances such as Calcium, Potassium, Magnesium, and Silica. There is usually not much fluoride, iron, or strontium, except in very unusual waters. There are FDA regulations about the allowable limits of certain minerals in natural (unprocessed) mineral water.
Low TDS waters are chemical microcosms of the High TDS waters. While the total mineralization is low, the relative distribution of suspended elements can vary greatly. In combination with the pH (see below) the presence or absence of certain elements will affect the taste of the water.
How do I decide whether it's better to drink a High TDS water or a Low TDS water?
Armed with the knowledge from the preceding FAQ, your choices relate to your specific requirements. It depends on what is most important to you or your guests - often, water lovers consume more than one brand for different purposes. In the COMPATIBILITY GUIDE TO WATERS & FOODS section of the web site, you will find useful guidelines when culinary considerations are your primary objective. For simple hydration, you may settle on a favorite Low TDS water, often in PET plastic packaging, as an ideal choice. And for many, water selection is dictated by benefits of a particular chemistry. For example, waters that are high in Calcium are good for people who suffer from, or seek to prevent, diseases relating to calcium deficiency. There's no right or wrong about TDS - it's all about choice and purpose.
What is "pH?"
pH is a term used in basic chemistry - it is literally an acronym for "potential of hydrogen." Without getting into scientific talk, pH can simply be thought of as a measurement of acidity and alkalinity. The full range of pH values is from 0 to 14. 7.0 is perfectly neutral. pH under 7.0 indicates acidity, and the lower the pH the more acidic the substance. pH greater than 7 indicates alkalinity (also referred to as a "base").
To give you an idea of the entire range, milk is slightly acidic at around 6.5, and seawater is alklinic to the tune of 8.5. Vinegar is more acidic at 3.0 and battery acid has a highly acidic pH of 1.0. Milk of Magnesia is alkalinic registering a 10.5 pH, and lye has a highly alkalinic pH of 13.
The maximum range of pH values in mineral waters is from just over 5.0 on the most acidic end of the scale, to around 9.5 on the most alkalinic side. Perrier is an example of a strongly acidic mineral water (pH of 5.5), and Trinity is one of the most alkalinic (pH of 9.6).
pH level most definitely creates a taste. An acidic pH produces a sour taste and tends to be apparent at once - sometimes referred to as a "front taste," whereas alkalinity presents itself as bitterness, and is more of an "aftertaste."
Is the water quality affected depending whether it is bottled in Glass, or in PET plastic?
You'll get some strong arguments on this question, but Aqua Maestro believes the honest answer is yes. Fortunately, for the most part, the difference is either so slight, or the water is consumed so quickly, that it does not make any practical difference. But there are notable exceptions.
First, an explanation of the oft-maligned PET. While PET is never the choice of connoisseurs when glass is available, it must be emphasized that there is nothing unsafe about drinking from PET. "PET," which stands for polyethylene terephthalate, is a plastic resin and a form of polyester (for the scientists: it is a polymer formed by combining two monomers called modified ethylene glycol and purified terephthalic acid). PET is a standard compound for containerizing food and beverage products because of its durable, non-reactive properties. For all practical purposes, nobody can or will ever get sick by consuming something that came out of a PET package.
Glass bottles come mainly in green and clear. Specialty colorings of cobalt blue and red are also seen - generally, any other color of glass is an application to the glass surface rather than being fired into the glass. Green glass and clear glass, as commodities, are similarly priced, but it is more expensive to manufacture cobalt blue glass and red glass. All bottled water glass meets the NSF Standard 53 requirements accredited by ANSI (The American National Standards Institute).
So - then what's the difference between mineral water in glass and mineral water in PET? There are two differences, one rather subjective, the other one very obvious. Although there are double-blind tests to the contrary, it is impossible for us at Aqua Maestro to ignore the body of opinion that a slight plastic taste somehow permeates the taste of water in PET. For still waters - waters that are not carbonated - the anecdotal complaints are fewer. And perversely, the taste of bottle tap waters and processed waters might even benefit from any such permeation. But with carbonated mineral waters, the complaints about the taste of plastic are more abundant; and then the second problem - the bigger obvious problem - arises. Carbonated mineral water in PET goes flat in a matter of months. Aqua Maestro tries, wherever it can, to avoid, buying carbonated waters in PET, because we know from first-hand experience about their short shelf life. Occasionally we have no choice because of availability, but we always opt for the glass when buying sparkling or naturally carbonated waters.