Abstract: Apparatus and a method for upgrading low pressure steam or brine, such as from a geothermal well, to prepare the steam or brine for any one of a number of uses, such as for conversion to pure, high pressure, high temperature steam for driving turbines. The system operates in a degasification phase in which a small amount of superheated steam is applied to the brine to scrub the same to cause the removal of concentrated gases therefrom. The degasified product is then pumped to a high pressure, heated countercurrently, and directed through a demineralized phase to remove the salts and solids in a liquid phase and convert the bulk of the water into pure, high pressure saturated steam. The steam output from the demineralizing phase can then be used to produce useful work, such as driving a turbine. In addition to forming saturated steam from geothermal brine, the system can be used to form pure saturated steam from impure water from any suitable source.