If your water has a moderate to high total dissolved solids content, it can affect the taste. Taste is very subjective and the ability to taste varies widely from person to person. However, the higher the TDS level, particularly when it reaches over 500 ppm (the recommended USEPA aesthetic guideline), the more likely people are to purify the water.
So how can water with high TDS be undesirable or harmful? It may taste bitter, salty, or metallic and may have unpleasant odors. High TDS water is also less thirst quenching. High TDS interferes with the taste of foods and beverages, and makes them less desirable to consume. Some of the individual mineral salts that make up TDS pose a variety of health hazards. The most problematic are Nitrates, Sodium, Sulfates, Barium, Cadmium, Copper, and Fluoride.
If a person drinks 2 pints of water a day, his or her body will have processed 4500 gallons of water over a 70-year span. Imagine if the water is not totally pure, these 4500 gallons will include 200-300 pounds of rock that the body cannot utilize! Most will be eliminated through excretory channels. But some of this will stay in the body, causing stiffness in the joints, hardening of the arteries, kidney stones, gall stones and blockages of arteries, microscopic capillaries and other passages in which liquids flow through our entire body.
The EPA Secondary Regulations advise a maximum contamination level (MCL) of 500mg/liter (500 parts per million (ppm)) for TDS. Numerous water supplies exceed this level. When TDS levels exceed 1000mg/L, it is generally considered unfit for human consumption. A high level of TDS is an indicator of potential concerns, and warrants further investigation. Most often, high levels of TDS are caused by the presence of potassium, chlorides and sodium. These ions have little or no short-term effects, but toxic ions (lead arsenic, cadmium, nitrate and others) may also be dissolved in the water.
Where do Dissolved Solids come from, after all? Some dissolved solids come from organic sources such as leaves, silt, plankton, and industrial waste, and sewage. Other sources come from runoff from urban areas, road salts used on street during the winter, and fertilizers and pesticides used on lawns and farms.
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Dissolved solids also come from inorganic materials such as rocks and air that may contain calcium bicarbonate, nitrogen, iron phosphorous, sulfur, and other minerals. Many of these materials form salts, which are compounds that contain both metal and nonmetal. Salts usually dissolve in water forming ions. Ions are particles that have a positive or negative charge. Water may also pick up metals such as lead or copper as they travel through pipes used to distribute water to consumers. You should note that the efficacy of water purifications systems in removing total dissolved solids will be reduced over time, so it is highly recommended to monitor the quality of a filter or membrane and replace them when required.
What are the different properties of High TDS and Low TDS mineral water? Higher TDS water has 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 water, particularly those with the very lowest TDS, has virtually no taste, and "expresses" an airy or light mouthfeel. Consumers describe the lowest TDS waters as tasting clean, with even a hint of sweetness. Natural water is like snowflakes - no two are exactly the same. Unlike processed water that is de-bacterized, homogenized, filtered, polished, and subjected to other procedures that ensure bottled products with 100% identical chemistry, natural water is organic and behaves 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 geology, climate, and other environmental and terrestrial factors.
High TDS water has a great variety of interesting chemistries. Some are heavy in Sodium, Bicarbonate, 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 water. 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 water.
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.
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