Golf Ball Test

Tile Tenting is when tile breaks loose from its base, sometimes it 2 pieces lift to look like a tent.  Other times the grout stays black weeks or months after it was wet.     

Take a golf ball or a wooden broom handle then tap on the floor.   Healthy tile sounds like a bat hitting a baseball.   A hollow sound indicates there is an air pocket between the tile and the floor, Tile failure.   Bacteria begins to grow in there and the problem will spread unless you perform a tile repair.