Nava was designed for use with potable water only. It will not remove harmful microbes, such as Giardia, which may be present in the tap water of some countries. We recommend only using Nava with potable tap water in the following areas: USA, Europe, Japan, Canada, Australia and New Zealand. Nevertheless we encourage you to ensure your water meets the equivalent or better of potable water in the U.S. for which the Nava was tested.