CSIDefender® Copper–silver ionization is a Legionella potable water treatment technology used for Legionella growth control and prevention. Larger commercial copper-silver ionization units such as CSIDefender® can be used for Legionella water treatment in either potable hot water distribution networks or point of entry applications. Legionella is a bacterium known to cause Legionnaires’ disease, a preventable form of severe pneumonia. Copper-silver ionization is recognized by the CDC, EPA and WHO. CSIDefender® is also commonly specified by consultant engineers for new construction projects and retrofits in existing facilities. C-ETL-UL, CSA, CE and NSF/ANSI61 on all wetted components.