Folks: I do maintenance on a couple commercial buildings. One is a 4 story building, 6 months old. One bathroom on the 4th floor is approximately 20 feet by 14 feet. It has two toilets in the corners and on the other wall 2 urinals and 2 sinks. What has happened is one toilet has started to malfunction by not flushing and draining when used. Instead of this toilet overflowing, there is a drain in the middle of the floor; and the crap and water comes up through the drain. This is causing a large area (25 sq. ft.) of this human waste. It has been scoped by a plumbing professional with no construction debris. Because this is the 3rd time it has happened, I have my concerns. Does anyone have an idea on what may be causing this?