This document specifies a test method and the minimum requirements for bactericidal activity of chemical disinfectant products intended to be used for treatment in aqueous systems against Legionella pneumophila that form a homogeneous, physically stable preparation when diluted with buffered ferrous hard water or hard water. Whenever Legionella pneumophila poses a risk to human health, this method is suitable for water used in cooling towers and water for general purposes, like spas, pools, showers and other uses. The method is not suitable for electro-chemical disinfection. The document applies to products used as a single application shock treatment in order to kill Legionella pneumophila. It is not suitable for the evaluation of those products that are dosed continuously into water systems to control the growth of Legionella pneumophila. NOTE 1 The method described is intended to determine the activity of commercial formulations or active substances under the conditions in which they are used. NOTE 2 This method corresponds to a phase 2 step 1 test. NOTE 3 This method does not take into account the fact that Legionella pneumophila is often found in cells of amoebae and/or biofilms and that thereby a product’s activity against the bacteria may be reduced. EN 14885 specifies in detail the relationship of the various tests to one another and to "use recommendation".