A carbonator or soda maker usually consists of a holder with a replaceable gas cartridge that contains 300–500 g of carbon dioxide, depending on the model. The water is poured into pressure stable bottles and screwed into the pressure-tight holder. With a button push the gas is injected into the water through a piping and valve system. The carbon dioxide content is regulated by the duration of the injection. Any overpressure generated in the water container is released if it becomes too high.