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A water ionizer (also known as a alkaline ionizer) is a home appliance which claims to raise the pH of drinking water via ionization; in order to achieve a variety of health benefits. Such claims contradict laws of chemistry and physiology and are unfounded.
The machines originally became popular in Japan and other Far Eastern countries before becoming available in the U.S. and Europe.
Despite being described as 'water ionizors' the machines are designed to work as water electrolysers. This is an electrochemical process in which water is split to form hydrogen and oxygen by an electric current. The overall chemical reaction is shown below:
During this process the water near the anode is acidic while the water near the cathode is alkaline. Water ionisers work by simply syphoning off the water near the cathode. This contains increased levels of hydroxide (OH−) and would be expected to have a higher pH (i.e. be more alkaline). The effectiveness of the process is debatable, as electrolysis requires significant amounts of time and power; hence the amount of hydroxide that could be generated in a fast moving stream of water (i.e. a running tap) would be minimal at best.
Water ionizors are often marketed on the basis of health claims; normally focused on their ability to make water more alkaline. A wide variety of benefits have been claimed, including the ability to slow ageing, prevent disease and even offer protection from nuclear fallout. There is no empirical evidence to support these claims, nor the claims that drinking ionized water will have a noticeable effect on the body. Drinking ionized water would not be expected to alter the body's pH, due to acid-base homeostasis.