It is difficult to breed parasites in tap water because it is disinfected with chlorine disinfectant, the disinfection time is relatively long-lasting, and it meets the national drinking water standards, but it is still not recommended to drink the cold tap water directly. Because most of the city’s tap water is still treated by a long time ago water treatment process, can not completely filter heavy metals and organic pollution, water pipes are also mostly iron pipes, there will be rust, iron ions will exceed the standard, it is recommended that high temperature disinfection before drinking. If the gastrointestinal tract is weak, drinking raw tap water at this time will cause diarrhea and other digestive symptoms, usually try not to drink raw water.