Most of current External Thermal Insulation Composite Systems (ETICS) is protected from microbial attack by use of biocides mostly in base or finish coat/paint however this protection is time limited. Leaching of these biocides is not controlled yet. There are various studies [1-5] examining possibilities of collecting and processing the wastewater, the others try to find out new bio-biocides without negative effects on the environment. Another point of view is regular maintenance of ETICS surface that is one of the most important factors of prevention of biocorrosion. The technology includes biocide decontamination processes, mechanical cleaning, rinsing of surface by a pressure cleaner and a preventive coating with a biocidal preparation. In this maintaining process, ambient environments are loaded with running water with detergents which are usually based on heavy metals. System designed to collect wastewater from the cleaned surface is currently considered as the most effective way to reduce unwanted effects of biocidal substances on the environment throughout the whole lifespan of ETICS.