In all my years of working in office buildings and attending concerts, I’ve never once seen a urinal overflow. This, despite the fact that most people apparently rarely flush the things, based on the bowl of lemonade I’m guaranteed to see every time I hit the loo.
Is there a technological reason for this? Is the urine drawn back into the pipes and held, or is there some other reason?
Perhaps I just haven’t been hanging out in the right men’s rooms.
Thoughts from our scientific flushers?
The drain on urinals either connects directly to the sewer line, or has an inline siphon trap like a regular flush toilet. In the first case, there’s nothing to stop fluid from going to the drain. In the second, the system operates like a flush toilet, once the liquid in the bowl, or the urinal gets high enough, the siphon operates, and the liquid is sent to the sewer.
Relatively new waterless/flushless urinals have an added cartridge with a liquid sealant to pass wattery waste and prevent bad odors from stagnant waste.
** Water Free or Flushless Urinals, Animated ** It also has the required trap.
Pretty much the same reason your kitchen sink doesn’t (usually) overflow. There’s a U-shaped trap in the urinal that keeps the water at a given level to block sewer gases and other nastiness from coming back up. Your sink has the same mechanism, however the water level is kept far below the drain where you don’t have to look at it. When the level gets high enough on your side of the urinal that it exceeds the height of the trap on the other side, some water will trickle through the pipe, keeping the level down. (I doubt you get a full siphon effect, though)
Or think about it this way… it doesn’t overflow from urine for the exact same reason that it doesn’t overflow when you flush it.