What device must be activated before opening the pool each day?

The device that must be activated before opening the pool each day is the test-buttons for ground current leakage. This is crucial for ensuring the safety of patrons who will be using the pool. Ground current leakage testing is a key safety measure that checks electrical systems in and around the pool area to prevent electrical shock hazards. By activating this device, staff can confirm that the electrical system is functioning correctly and safely before allowing anyone into the water.

Water filtration systems are essential for maintaining water quality, but they don't need to be tested in the same manner as ground current leakage devices. A back-up power generator, while important for maintaining operations in case of a power outage, is not typically a daily requirement before opening the pool. Swimming aids are also not related to safety checks and do not serve a preventative function for electrical hazards. Thus, the focus on ground current leakage testing underscores the importance of electrical safety in aquatic environments.