The water management law (WHG) and the plant regulations of the German federal states stipulate boundary conditions which must be observed during work on plants handling substances which are hazardous to water, There are various possibilities for the implementation of the legal provisions, During maintenance and cleaning work on chemical plants, our aim must be to provide effective protection of our waterways and to ensure that the operating procedures are also efficient in economic terms, Procedures which have been tried and tested in practice are described, The annex gives a compilation and explanations of extracts from legal texts from the field of water legislation which are of relevance in carrying out such work.