A safety apparatus (1) for a swimming pool (10) comprises at least two pressure switches (31,41) in use hydraulically connected in a same point (22) upstream of a pump (25) of a swimming pool water purification circuit, each pressure switch comprising a first (33,43) and a second (34,44) contact arranged to open or close when an emergency stop pressure (P<；sub>；a<；/sub>；) and a maximum operation pressure (P<；sub>；e<；/sub>；) is reached, respectively, and also comprises a logic unit (50) electrically connected to each pressure switch (31,41) and, in use, with a contactor (24) of the circulation pump (25), the logic unit (50) configured to compare the statuses of the second contacts (34,44) with each other, and for transferring a pump-stop/block electric signal (55) to the contactor (24) when a status of at least one pressure switch (31,41) it is detected which corresponds to a pressure lower than the emergency stop pressure (P<；sub>；a<；/sub>；), or when a condition is detected in which the status of the second contact (34) of one of the pressure switches (31) indicates a suction pressure lower than the maximum operation pressure (P<；sub>；e<；/sub>；), while the status (44) of the other pressure switch (41) indicates a suction pressure higher than the maximum operation pressure (P<；sub>；e<；/sub>；)； in this condition, an instrument out-of-service alarm signal is also generated. In an exemplary embodiment, a key device is provided, associated with a key confidentially entrusted to a subject, which serves allow switching on the pump even in the presence of such a condition.
