it’s enough that one pad is covered with a water drop. there are small traces and if they are shorted with a water drop the device sends an alarm.
the sensor can be positioned relativeley flat on the ground. there is a hole for a screw. if you want to put it flat on the floor you just need to rewire it. the wires to the sensor are lead through holes for cable relief.
desolder them and pull the wires out of the holes and resolder on the top and you can put it flat on the ground.
i can take some pictures l8r