We have developed the pure water and functional water system for household use that provides pure water by RO and saves water consumption by producing mild alkaline and acidic water with electrolysis of rejected water from RO. Pure water shows excellent abilities in scale inhibition and reducing the amount of detergent in laundry washing. Natural detergent, less than a half of standard amount, has still demonstrates sufficient cleaning ability when it has used with pure water, which suggests the decrease of burdens on the environment. Alkaline and acidic water has shown effective decomposition of alkaline degradable agrichemical and sufficient sterilization abilities, respectively.