It is safe to drink tap water in Japan?

Answer 1

Yes, it is basically safe to drink. Tap water in Japan is treated with ozon or chloride. Amounts of chemicals used in treatement vary according to the quality of the water sources. Tap water in mountainous areas (ex. Nagano pref) where small amount of chemical is needed, is particularly famed for its "sweetness". The water gets tastier recently in Tokyo where use of chloride in treatement is mostly replaced with other method such as ozonization. In rare cases tap water can taste bad when the pipeline in the building gets rusty or the water tank of the building is badly maintained, for example the lid of the tank is moved open, letting everything from the sky to drop inside! In such cases boiling the water to have a cup of green tea might be a better option compared with just drink it directly from the tap, but just go find a bottle of water at a ubiquitous convenience store. For some (particularly elderly) people in the country, tap water is believed to cause an obscure long term health hasard due to chloride-derived carcinogenic compound such as tryhalomethane and other chemicals and buy drinking water at the supermarket where water treatment machines said to remove such chemicals are installed. However, at least accute hasard such as epidemics of infection or incidents of heavy metal poisoning is almost unheard of for 30yrs.