High-end foreign-related business apartment. There are 25 floors in total. The water supply for customer rooms is provided by a variable frequency pump for high-floor water supply. Galvanized pipes are mainly used. After eight years of operation of the pipes and equipment, the inner walls of the pipes have become corroded. The bathtubs and kitchen faucets in the apartments have serious red water, and some mud is entrained. Sand, reddish brown rust stains are obvious in the pipes of the boiler water piping system.