Copper tank to hold water that must be filled up to the indicator line of the glass tube placed at the back of the Lucas Championnière sprayer. When the sprayer is plugged in, with the switch in the "ON" position, the water contained in the boiler will heat up and rise in temperature. A vacuum will be created by the Venturi effect, allowing the solution previously placed in the glass cup (on the "handle" side of the Lucas Championnière sprayer) to be sucked up and sprayed.