Fumes from dirty pipes can sometime come up and leave the house smelling like a sewer. Through interconnecting household piping systems, this foul smell can move from room to room until it fills the whole house. Another concern is the germs, molds, and bacteria that dirty pipes may harbor. Microorganisms are a grave health hazards and can cause a number of illnesses to your family. When you are preparing food, germs can go into the food, contaminating it. Thus, it is necessary to keep your pipes clean.