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Customers often wonder how exactly a septic system works, so I thought I would shed a little light on the subject!

What is a Septic System?

Septic systems are underground wastewater treatment structures that collect, treat, and disperse wastewater that has been created by a home or business. Because waste is treated on-site, septic systems are commonly used in rural areas and other places without centralized sewer systems.

Septic systems use a combination of nature and proven technology to treat wastewater from household plumbing produced by bathrooms, kitchen drains, and laundry.

How Your Septic System Works

A typical septic system consists of a septic tank and a soil absorption field, also known as a drain field or leach field, with underground pipes that connect the entire system. You can see a diagram of a typical conventional system below.

diagram of a conventional septic system

The septic tank is a buried, watertight container that is usually made of concrete, polyethylene plastic, or fiberglass. Wastewater flows from the home or business through one main drain pipe into the tank, which holds the wastewater long enough for its contents to settle out in layers and partially decompose.

Inside the tank, solid waste settles out to the bottom to form sludge, while fat, grease, and other lipids float to the top to form a layer of scum. Bacteria and enzymes then digest most of the solid waste and break down the fat layer. Compartments inside the tank and T-shaped outlets called baffles prevent the sludge and scum from leaving the tank and traveling into the drain field area, while the watery middle layer (known as effluent) is free to flow out to the absorption field.

septic tank diagram

The drain field is a shallow, covered excavation made in unsaturated soil. Pretreated wastewater is discharged through piping onto porous surfaces that allow wastewater to filter though the soil, which accepts, treats, and disperses it before ultimately discharging to groundwater.

That’s really it! Of course, the specific technical requirements of your septic system can get a lot more complicated, depending on local environmental ordinances, composition of your soil, depth of those soil horizons, surrounding topography, the presence of additional structures, and your proximity to lakes, rivers, and watersheds. To see what I mean, check out the nine major types of septic systems.

A Word of Warning

Septic systems can be an economical and sustainable way to treat wastewater, but under the wrong circumstances, they can also contribute to groundwater and/or surface water contamination. This could result from any combination of factors including improper location of the components, poor design, faulty construction, incorrect operation, and poor maintenance.

For instance, if the drain field is overloaded with too much liquid, it can flood, causing sewage to flow to the surface or even create backups in toilets and sinks – all of which can lead to a serious environmental hazard in and around your home or place of business.

This is why it is so important to work with a qualified septic system professional when buying or building a home that will need a septic system. By creating the right septic system and keeping it in good working condition, you can save money, increase the value of your home, and feel good about helping the environment.

Above images courtesy of the EPA.

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