Mold and mildew love damp and wet areas, especially when there’s not a lot of light or air movement. A lot of leaks happen behind a wall, under the floor or in the ceiling where they go unnoticed for quite a long time. And these places are the perfect breeding ground for mold and mildew. If you notice mold or mildew growing on a non-shower wall in your house, this could be a telltale sign of a water leak. Turn off your water and call a plumber immediately to schedule a leak detection service.