Facilities that handle substances hazardous to water (e.g., heating oil systems, gas stations, …) must be reported to the competent water authority and inspected by a qualified body, depending on their hazard potential, their configuration (above-ground, underground), and their location within a protected area (water protection zone, mineral spring protection zone, or floodplain). The legal basis for this is the Installation Ordinance (VAwS).

For example, above-ground heating oil systems with a storage capacity of more than 1 m³ must be inspected prior to commissioning, as well as periodically and upon decommissioning if located within a protected area; underground heating oil systems must generally be inspected prior to commissioning, periodically, and upon decommissioning. Systems in which other water-polluting substances are stored are subject to tiered inspection requirements, depending on the hazard level.

The inspections are conducted by accredited inspection bodies in accordance with § 22 VAwS and supervised by the competent water authorities.
Accredited inspection bodies may operate within the scope of their accreditation. Accreditations may be limited to specific inspection areas or be time-limited. Accreditations from other federal states are also valid in Hesse.

Accreditations from other member states of the European Union, a signatory state to the Agreement on the European Economic Area, or Switzerland are considered valid if their equivalence has been determined by the accrediting authority and published in the Official Gazette of the State of Hesse.