There is disclosed a system for cooling a water-cooled apparatus having a water inlet and a water outlet. The system has: a circuit in fluid communication with the water inlet and the water outlet, the circuit having a valve upstream of the water inlet connected to a source of water, and an outlet in fluid communication with a sewer; an air-cooled cooling unit in heat exchange relationship with water in the circuit; and a pump fluidly connected to the circuit; the system operable between a closed-loop configuration and an open configuration, the valve being closed and the pump circulating water between the water-cooled apparatus and the air-cooled cooling unit in the closed-loop configuration, and the valve being open and water in the circuit circulating from the source of water, through the water-cooled apparatus, and to the sewer in the open configuration.