Development of a standard for purifying storm water Many of the technical solutions for stormwater treatment available on the market are often marketed with reference to high purification potential and low maintenance needs. However, there have rarely been independent tests or evaluations that prove the actual performance of the technics. It is a complex decision for the end user to choose the right technology and/or manufacturer for a particular application and purpose, while ensuring long-term functionality. At present, there is no Swedish standard, but many clients of stormwater technology refer instead to the Swedish Water and Wastewater Association's publications or to their own example collections for stormwater measures and design criteria that should apply to construction. Other countries, like The United States, Germany and the United Kingdom national standards for testing and evaluating the degree of purification of prefabricated stormwater solutions exists since a number of years. Since 2018, RISE has worked for the development of a Swedish standard together with a number of actors in the industry and with financial support from the Swedish Environmental Protection Agency (Stenvall & Sörelius (2021), Klingberg & Kusoffsky (2021) and Dahlberg, etc. (2022)). In this project (November 2023), RISE, with the support of the Swedish Environmental Protection Agency, together with Luleå University of Technology and GS Water Forum, has further developed the Swedish proposal for a National standard. The plan is to further test the standard in a German test facility by spring 2024. In order to provide the greatest possible market advantage for manufacturers who test their products according to the standard, the Swedish proposal has taken the German original into account. This is to ensure, as far as possible, that a supplier/manufacturer who has tested its product according to the standard will be able to gain access to both the German and the Swedish market. The work has also been carried out with the support of the Swedish Institute for Standards (SIS) to pave the way for the establishment of a Swedish Standard (SS) in 2024. This process will be initiated after the proposed test method has been evaluated in Germany.