ISO 11731:2017 specifies culture methods for the isolation of Legionella and estimation of their numbers in water samples. These methods are applicable to all kinds of water samples including potable, industrial, waste and natural waters. These methods can be used for water related matrices, e.g. biofilms, sediments, etc. Not all Legionella species are culturable; therefore, the methods described in this document do not recover all species of Legionella.