Think of a septic system as a stomach buried in the ground. Its purpose is to digest and dispose of household wastes so they are no longer a threat to the environment.

Septic systems are really ingenious creations, doing the work of giant municipal waste disposal sites but in your backyard.

A well-designed system emits no odors, is safe and doesn’t require huge amounts of maintenance. It relies on processes in nature to do the work.

A septic system’s first task is to separate liquids from solids, and this process takes place in a giant tank buried in the ground and connected to the house. Tanks are typically made of cement, plastic or fiberglass and can hold several thousand gallons.

As the waste flows into the tank, the solids sink to the bottom and the liquids then flow to a second tank.

Task No. 1: Breaking down solids

The solids are broken down by anaerobic digestion, a process in which microorganisms contained in the waste naturally feed on the waste and convert it to carbon dioxide, hydrogen, ammonia and other non-toxic substances.

This process greatly reduced the volume of solid wastes, leaving behind a sludge composed of indigestible substances, much as a fire in a fireplace leaves behind ashes after a log is burned.

Over time this slug will build up, reducing the efficiency of the septic system. The owner then calls a septic maintenance company, which sends a specially equipped truck that sucks the waste from the tank.

That may be necessary only every few years, but if it’s not done the risk is that the wastes will overflow and contaminate the rest of the system, requiring extensive and costly repairs.

Task No. 2:  Disposing of liquids

When it comes to waste liquids, septic systems essentially rely on Mother Nature to process them.

The liquids are released from the second tank into a grid of pipes with holes in them laid out in a field some distance from the house. The liquids seep into the soil, which filters out or neutralizes most or all of any contaminants that remain, including coliform bacteria, the bacteria found in the human stomach that enables digestion.

Coliform bacteria can be a major health risk, and if untreated can lead to a raft of illnesses, so removing it especially critical.

The remaining liquid, now fully filtered, drains into ground water, where it feeds trees and plants.

For drainage field to do its job properly, it must be large enough to accommodate  the flow of waste water, and the soil must be porous enough to ensure proper filtration. Otherwise there’s a risk that the liquid will overwhelm the system, causing flooding, which can causes backups at the house.

Fields can run 100 feet or more in length, with the drainage pipes buried several feet below ground and typically spaced several feet apart.


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