How Septic Works
A residential septic system is an on-site wastewater treatment system used in homes not connected to a public sewer system, typically in rural or suburban areas.
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It functions by collecting wastewater from household plumbing, including toilets, sinks, showers, and laundry through a main drainage pipe that leads to a buried, watertight septic tank.
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The tank, usually made of concrete, fiberglass, or polyethylene, holds the wastewater long enough for physical and biological processes to occur.
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Inside the tank, wastewater separates into three distinct layers: solids settle at the bottom forming sludge, oils and grease float to the top creating a scum layer, and a middle layer of relatively clear liquid, known as effluent, remains.
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Baffles or a T-shaped outlet prevent sludge and scum from exiting the tank and entering the drain field.
The effluent then flows from the tank into a drain field, also known as a leach field or absorption field, which consists of perforated pipes laid in gravel-filled trenches.
The drain field is a shallow, covered excavation in unsaturated soil designed to slowly release the effluent into the ground.
As the effluent percolates through the soil, it undergoes further treatment through filtration, chemical reactions, and decomposition by soil microorganisms.
This natural process removes harmful pathogens, such as coliform bacteria and viruses, and reduces nutrients like nitrogen and phosphorus before the water reaches groundwater.