I hear a drip inside my walls behind the main bathroom, however, the washer/dryer closet is directly behind that wall and the second bathroom is also. Where should I start? By the way the house is a 39 yo slab home. The laundry closet was redesigned aprox 1 yr ago at which time the washer/dryer lines were relocated. I really need the least expensive as well as least demo solution or starting point.