Deutsche Bahn trains operate daily in regional and long-distance traffic and are exposed to various weather and environmental conditions. To ensure clear visibility for passengers and drivers at all times, the trains are regularly cleaned in washing plants. In most plants, the wash water is recycled. Up to 60 percent of the used water can be reused. In Berlin-Grünau, a new washing plant for the new S-Bahn Berlin trains was put into operation, which can even reuse up to 90 percent of the service water used.

In many locations, the wash water is also biologically treated using bacteria. Where possible, Deutsche Bahn also uses well or rainwater to conserve valuable drinking water. Additionally, nearly neutral cleaning agents are used in several DB washing plants. This reduces environmental impact and lowers the costs of water treatment.