Alarms adaptable to common American 
bathtub cover plate configurations. Two different embodiments are illustrated. In a first embodiment, the alarm unit is designed to allow use with the three different mounting styles of cover plates used in the United States. The 
unit housing is preferably formed of plastic or 
metal with different colors and finishes and includes removable areas to allow use with a 
single center screw; dual screws or a center pivoting drain lever with dual screws. The various 
electronics components remain sealed inside the waterproof plastic or 
metal housing in all instances. In a second embodiment, a waterproof housing attaches to an adapter ring. The adapter ring is configured to cooperate with 
single center screw and dual screw variations. An alternative adapter ring can be used with European and newer American threaded overflow drains. In the first two embodiments there can be upper and lower sensor(s), preferably a pair of each, to provide initial and critical warnings. The warnings include audible warnings emitted by the alarm unit as well as transmitted signals for detection by remote devices.