I recently installed a toilet in the basement. the rough was done when I built the house 11 years ago. Whenever we use the first floor washing machine, when the tub empties, air bubbles come out of the basement toilet. The water level receeds to the point where it is even with the bottom of the bowl. Is this anything to worry about/ Can the problem be solved? Would some sort of vent on the drain hose for the washing machine solve it? Please help?