It is a “watertight” container, usually made of concrete and buried somewhere in your yard. The septic tank separates the solids from the liquids. Most of the solids settle in the tank and will need to be removed periodically by hiring a licensed professional to clean the tank. Newer tanks contain a dividing wall, which separates the tank into two compartments. All tanks should have an inlet baffle and outlet baffle to keep the scum and sludge inside the tank. Learn more about standard septic systems.