You require a permit

• in the catchment area (Zone I) and in the narrower protection zone (Zone II) of water protection and source protection areas,
• on areas of harmful soil changes, suspected areas, contaminated sites and sites suspected of being contaminated within the meaning of the Federal Soil Protection Act and
• for rainwater from copper, zinc or lead-covered roofs that have not been coated or treated in a similar way.

The harmless decentralised disposal of rainwater does not require a permit in the following cases:

• Rainwater accumulates on the following areas:
  • Roof surfaces
    Exception: Roof surfaces in commercial areas and industrial areas as well as special areas withcomparable uses
  • paved property areas
    Exception:areas used for commercial, craft andindustrial purposes
  • public roads that serve as local roads for the development of residential areas and public roads outside the built-up area
    Exception: carriageways and car parks of roads with more than two lanes
  • restricted public paths and footpaths and cycle paths that are part of a public road
• They infiltrate the water into the groundwater over a large area or in troughs on vegetated ground at least 30 centimetres thick.
• The decentralised disposal of rainwater is provided for in building planning or building regulations.

You must report the unauthorised discharge of rainwater,

• if it comes from paved or built-up areas of more than 1,200 square metres and
• the water authority has not already become aware of the project in other procedures.

Exceptions are possible.