Septic systems or on-site wastewater disposal systems are underground wastewater treatment structures that use a combination of nature and technology to treat wastewater from household plumbing produced by bathrooms, kitchen drains, and laundry. A typical septic system has four main components: a pipe from the home, a septic tank, a drainfield, and the soil. Microbes in the soil digest or remove most contaminants from wastewater before it reaches ground water. The septic tank holds the wastewater long enough to allow solids to settle out and oil and grease to float to the surface. Tanks are designed to prevent sludge and scum from leaving the tank and traveling into the drainfield. Malfunctioning systems due to improper design and/or maintenance can release bacteria, viruses, and chemicals to ground water. Additionally, wastes disposed of improperly into septic systems can adversely impact operation of the system and contribute to ground water contamination. Septic systems are common in rural areas without centralized sewer systems.