PURPOSE: To remove adsorbed materials easily without damaging porous membranes of water treating devices for obtaining pure water or germ-free water by washing the membranes by using alcohols.
CONSTITUTION: The porous membranes of water treating devices for obtaining pure water or germ-free water are formed of PE, PP, etc., and when the membranes are used in water treatment, lipophilic materials contained in trace amt. in raw water, for example, higher fatty acids, higher fatty acid esaters, and phthalic esters stick thereon. Such stuck materials are washed awya with alcohols. Methyl alcohol, ethyl alcohol, allyl alcohol, etc. are used as alcohols, and are used as 100% alcohol or ≥30% aq. solns.