This paper presents the copper oxidation and flowing out characteristics inside copper pipe line, which is a candidate for future cooling water pipe line, with various species of dissolved gases in cooling water. The result reveals that copper oxidation rate in air saturated ultrapure water is much faster than other conditions, whereas its rate in hydrogenated ultrapure water is not differentiated from that in de-Aerated ultrapure water. However, the amount of copper flowed out from the pipe surface is drastically reduced by using hydrogenated ultrapure water. The data indicate that copper in neutral pH solution with the oxidation reduction potential (ORP) value of 400 mV such as hydrogenated ultrapure water is perfectly stable for surface oxidation. As a cooling water has many kinds of advantages: it is not necessary to use chemicals as anti-corrosive agents; there is no cooling efficiency degradation by oxidation inside pipe line surface, and a "maintenance-free system" can be realised. A newly developed cooling system using hydrogenated ultrapure water is applicable to other industry facilities as well as semiconductor fabrication with major benefits in terms of the "industrial cost" and "the environmental issues".