This man is filling the cans with distilled water. It is in these cans the ice is made. On the bottom of the tube you see held in its place in the can with braces is a valve, opening upward. When this valve is pressed against the bottom of the can it lets out enough water to fill the can almost to the top. When the water reaches a certain height it is stopped by a floating check valve. A floating check valve is one which has a hollow metal ball attached so that when the water in which it floats reaches a certain height it turns the valve and either shuts off the water or releases it, as desired.