NOVELTY - The water electrolysis installation comprises a hydrogen pressure-reduction removal apparatus (12) for reducing pressure in hydrogen-water separator to remove the gas contained in the water, pressurization force feeding pump (14) for pressurizing water and supplying the water to water container (1), and water cycle pump (16) which circulates the water pressurized by a water pump through oxygen-water separator.    USE - For electrolyzing and storing water in the form of hydrogen and oxygen.    ADVANTAGE - The water electrolysis installation is compact and prevents the contact and reaction of oxygen and hydrogen. The ON-OFF frequency of each structure apparatus is decreased, thus the installation is durable.    DETAILED DESCRIPTION - The water electrolysis installation comprises a hydrogen pressure-reduction removal apparatus for reducing the pressure in hydrogen-water separator to remove the gas contained in the water, pressurization force feeding pump for pressurizing the water after pressure-reduction removal and for supplying the pressurized water to water container and a water cycle pump which circulates the water pressurized by a water pump through oxygen-water separator. Water in a water container is pressurized and supplied to water electrolysis stack (3) by water supply pump (2). The water electrolysis stack decomposes one portion of water to hydrogen gas and oxygen gas. Water containing hydrogen is separated to water and hydrogen gas by hydrogen-water separator (4) and oxygen-water separator (5) separates water containing oxygen. The pressurized gases are stored in each storage tank (7,8).    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram of the water electrolysis installation.    Water container (1)    Water supply pump (2)    Water electrolysis stack (3)    Hydrogen-water separator (4)    Oxygen-water separator (5)    Storage tanks (7,8)    Hydrogen pressure-reduction removal apparatus (12)    Pressurization force feeding pump (14)    Water cycle pump (16)