I am renovating a bathroom in a condo and the wall behind the toilet and sink is shared with the laundry room. When I removed the toilet and sink and took out the drywall I noticed the continuous flow trap seal primer from the washing machine is overflowing and running down the outside of the pipe any time the washer is on. I just learned about trap seal primers and have no clue how any of this works. Is it possible it is overflowing because the toilet and sink are out and their water flow cut off or should I be concerned about a clog below floor level?