What is a septic tank?

Septic tanks explained

Septic tanks are underground holding tanks for wastewater (liquid waste that can include toilet waste, dirty kitchen water and water from clothes washing machines).

They process the wastewater by separating liquids from solids. Wastewater enters the septic tank through an inlet pipe. It is deposited in the tank through a dip pipe.

As the wastewater builds up in the tank, heavier solids sink to the bottom of the tank, while lighter solids, including fats and oils, collect on the surface. This leaves liquid effluent in the middle.

Another dip pipe, usually located on the other side of the tank, then draws off the liquid effluent which is usually dispersed into the ground via a drainage field, leaving the scum and the sludge inside the tank.

At regular intervals, before the tank becomes too full, this waste must be pumped from the tank and taken by tanker to be disposed of at an authorised waste site.

Some septic tanks have just one chamber. Others are designed with two or, sometimes, three chambers to improve the filtration process.

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