Septic systems use a digestion box that allows bacteria to decompose organic waste. The liquid waste flows to a drain field and slowly moves down into the groundwater. Failing systems can release bacteria, raw waste and household chemicals into groundwater. Even properly working systems add nitrate to groundwater. If the drain field becomes clogged, the “treated” sewage cannot percolate downward and it will pool on the surface of the ground. In the worst cases, the wastewater in the digestion tank may even back up into the house.

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