A water ionizer (also known as an alkaline ionizer) is a household appliance that increases the pH of drinking water using electrolysis to separate the incoming water stream into acidic and alkaline water. The alkaline stream of treated water is referred to as alkaline water. The second stream is considered waste and flushed down the sink.

Proponents claim that consuming alkaline water results in a variety of health benefits, making it similar to the alternative health practice of alkaline eating.

The Meditech Europe water ionizer One is a very nice looking device with all the specifications that belong in a top quality ionizer.

The specifications:

Although described as ‘water ionizers’, the machines are designed to work as water electrolysers. This is an electrochemical process in which water is split into hydrogen and oxygen using an electric current. The whole chemical reaction is shown below:

2 H2O(l) → 2 H2(g) + O2(g)
During this process, the water near the anode is acidic while the water near the cathode is alkaline.

2 H2O + 2e- → H2 + 2 OH- (at the cathode)
2 H2O → 4e- + O2 + 4 H+ (at the anode)
Water ionizers work by simply sucking out the water near the cathode. Water drawn from the cathode side contains elevated levels of hydroxide (OH-) and is likely to have a higher pH (i.e. be more alkaline), while water drawn near the anode has elevated levels of H+, making it acidic. The acidic water is said to be useful for household disinfection.

The effectiveness of the process is disputed because electrolysis requires significant amounts of time and energy; therefore, the amount of hydroxide that could be generated in a fast-moving stream of water, such as a running faucet, would be minimal at best. In addition, the process of reversing the reaction requires much less energy, so if the area between the alkaline and acidic water is at least semipermeable, the water will undergo another reaction leaving only neutral water. The second reaction is shown below:

H+ + OH- → H2O