The atmospheric drain tank (ADT) normally drains to the _______.

The atmospheric drain tank (ADT) is primarily designed to collect condensate water from various systems aboard a vessel, often from the main or auxiliary condensers in a steam system. The condensate that accumulates in the ADT typically needs to be returned to the boiler or the system to maintain efficiency and ensure proper operation. Draining to the main and/or auxiliary condenser allows for the reuse of this valuable resource, helping to conserve water and maintain the thermal efficiency of the system by allowing condensate to be reintroduced into the cycle.

In contrast, options such as draining to a sewage treatment plant, overflow storage tank, or sea do not appropriately utilize the condensate and do not align with the operational purpose of an ADT, which is focused on maintaining system efficiency rather than disposal.