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Bottled water must be tested and meet regulatory standards before it can be sold in the U.S. Most bottled water comes from a ground water source, where water quality varies less from day to day and typically less vulnerable to contamination than water from surface sources. However, ground water can still contain naturally high amounts of certain contaminants, including radioactive elements, arsenic, and nitrates, or be vulnerable to contamination from human activities, such as industrial waste, faulty septic systems, and underground gas or chemical tanks.
Moreover, some bottled water comes from surface water sources. Bottled water from a surface source or plant may have a more consistent taste than tap water. Public water system that use surface water sources typically receives additional treatment, such as filtration and disinfection. If bottled water is fluoridated due to the source of the public water system or naturally occurring fluoride, it must indicate so on the label.
The key difference in taste between tap water and bottled water is due to how the water is disinfected. Tap water may be disinfected with chlorine, chloramines, ozone, or ultraviolet light to kill disease-causing germs. Water systems use this disinfectant chlorine and chloramines because they are effective and inexpensive, and they continue to disinfect as water travels through pipes to homes and businesses. Bottled water that is disinfected is typically disinfected using ozone or other technologies such as ultraviolet light or chlorine dioxide. Bottlers prefer ozone, though it is more expensive than chlorine, it does not leave a taste. And, bottlers do not need to worry about maintaining disinfectant in water sealed in a container. Untreated water, whether from a bottle or from a tap, will have the characteristic taste of its source.
- Distillation- water is boiled, and the steam is condensed to remove salts, metals, minerals, asbestos, particles, and some organic materials. Microbes are killed, including Cryptosporidium.
- Micron Filtration- water is filtered through screens with microscopic holes. The smaller the filter holes, the more contaminants the filter can remove. Good filters can remove most chemical contaminants and microbes. Filter holes are measured in microns. (The period at the end of this sentence is 500 microns.) When considering filter size, look for an absolute (the largest hole), not nominal (the average hole) rating. An absolute one-micron filter is needed to remove Cryptosporidium.
- Ozonation- water is disinfected using ozone, which kills most microbes, depending on the dosage applied.
- Reverse Osmosis- water is forced under pressure to pass through a membrane, leaving contaminants behind. This process removes all microbes, minerals, color, turbidity, organic and inorganic chemicals.
- Ultraviolet (UV) light- water is passed through UV light, which kills most microbes, depending on the dosage applied.
Bottle water producers must operate their plants in accordance with FDA’s good manufacturing practices to ensure that their bottled water products are safe and produced under safe and sanitary conditions. If you would like to know in detail what is in your bottled water, you can contact the brand of the bottle water directly, ask for its latest testing results, and compare these results with EPA’s tap water standards or FDA’s bottled water standards to determine its quality.