Why is it advised in some countries in South America, such as Perú or Bolivia to avoid tap water and ice to drink? Is there a problem with the water filtration system and what are the dangers of drinking tap water and ice there? I have also heard about not drinking tap water in the Philippines, Bangladesh, etc., but is this the same problem as in countries in South America? In developed countries the only tap water problem I have heard is the mineralisation may cause upset stomach, but not tap water other problems.