Septic tanks are self-contained sewage depositories. In areas where municipal sewage systems don't reach, septic tanks are buried in the ground not far from a home's sewage outlet. A pipe drains all wastewater from the home to the septic tank, where human waste and other matter settle to the bottom of the tank while the grey and black water (terms that describe the types of waste water) filter through the tank and into a drain field. Septic tanks rely upon aerobic bacteria to break the waste down. Septic tanks and sewage systems similar to septic tanks have been around for a long time.

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Modern septic tanks are made of cement and drain into leach fields.

Cinder Block Cesspool

The cesspool came about after indoor plumbing. There needed to be a way to remove all the water being pumped into the home. A cesspool was a deep pit lined with cinder blocks. It had a natural bottom, and the waste and liquid were allowed to seep into soil out of the base and chinks in the cinder blocks. These cesspools were often dug so deep that they would contaminate the water table below, in turn making people sick. In the 1960s it became apparent that old cesspools had polluted our groundwater, causing changes in building codes to increase septic area requirements.

Brick Septic Tank

This version of a septic tank has a seepage pit instead of a drainage field. Both the tank and the pit are built of brick and mortar. Old brick septic tanks are rare because the brick breaks down over time. In such an instance, it is normally easier to install a newer model than to re-brick the former containment. Replacement of brick septic tanks was necessary sometimes after less than a decade of use, so entrepreneurs began looking for a more durable material for septic systems.

Steel Septic Tank

In the mid 1970s steel replaced brick septic tanks and ushered in the arrival of the drainage field. A septic drainage field is a trench with gravel in it and enclosing a pipe. The aerobic bacteria in the soil break down the waste, and the soil filters it out. Steel septic tanks turned out to be impractical because they rust when exposed to moisture. There is no way to keep a septic tank dry, so the inevitable happens: They crack and fail. Modern septic tanks are made of concrete, plastic or fiberglass.