Is it OK to submerse trap outlets?
Trap outlets should not be submerged as a general rule. If submerged, there is the danger that a vacuum will form inside the trap or at the trap inlet when the equipment is shut down, causing water to be sucked back up. This is not a problem if only water is sucked up, but if particulate matter such as dirt or sand is also sucked up, it can result in problems. If for some reason the outlet must be submerged, make a small air-intake hole in the piping to prevent the formation of a vacuum.
