A septic tank is a watertight box that is build under the ground. It separates the liquids and solids, provides digestion of some organics and storage. It discharges partially filtered and clarified effluent to the drain-field for final treatment. Buildings with plumbing facilities, not connected with the city sewer system use the septic tanks to dispose the wastewater.  In the images bellow you’ll see a diagram that shows clearly every main detail of the septic tank, and schematic conventional septic tank elements.

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