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From the Field

How a Septic System Works

By Ryan Chastain, Licensed Master Plumber Updated November 7, 2026

If your house is not on city sewer, a septic system quietly treats every flush and every drain. Here is how it works, and what goes wrong.

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Short answer: a septic system is a buried tank plus a drain field. The tank holds wastewater so solids settle out, and the clearer liquid then flows out into the soil.

  • What it is: a watertight tank and a field of buried pipes in the soil. No city sewer is involved.
  • Who it applies to: homes without a city sewer line, which includes many homes outside town limits in the North Georgia mountains.
  • Can wait: a drain that is a little slow, as long as nothing is backing up. Mention it to Ryan soon.
  • Call or text right away: sewage in a toilet, tub or shower, wet or smelly ground over the tank or field, or an alarm going off on a pump tank.

The two big parts: the tank and the drain field

Every conventional septic system has two main parts. The first is the septic tank, a buried, watertight container, usually made of concrete, fiberglass or plastic. The second is the drain field, also called the soil absorption field, a shallow dug area of buried pipes where the liquid soaks into the ground.

Everything that goes down your drains runs through one main pipe from the house into the tank. The tank is not a storage bin that fills up and stays full. Liquid comes in, and the same amount of liquid leaves, heading to the drain field.

What happens inside the tank

Wastewater sits in the tank long enough for the heavy solids to sink to the bottom. That layer is called sludge. Grease, oil and light solids float to the top and form a layer called scum. The middle layer is mostly liquid, and that liquid is what moves on to the drain field.

Natural bacteria in the tank break down some of the waste. They do not remove all of it. Over the years, sludge and scum slowly build up, which is why a tank needs to be checked and pumped by a septic pumping company on a schedule.

What the baffles do

Baffles are the walls, compartments or T-shaped fittings inside the tank at the inlet and outlet. Their job is simple. They keep sludge and scum from leaving the tank and flowing into your drain field. If an outlet baffle breaks or rots away, solids can slip out and clog the field, and a clogged drain field is a serious repair.

You cannot see baffles from the surface. A septic professional looks at them when the tank is open for pumping or an inspection.

Septic acting up?

Text Ryan a photo of the alarm, the wet ground or the drain. He is a licensed Master Plumber, and he answers his own phone, day or night.

Call (706) 669-5727 Text Ryan

The drain field: where the water finishes its trip

From the tank, the liquid flows through pipes into shallow trenches or chambers in the soil. The soil does the final cleaning. Microbes in the ground finish treating the water as it filters down. This only works if the soil is dry enough to take the water in, which is why a drain field needs to be kept free of driveways, heavy vehicles and extra water.

If a drain field gets more liquid than the soil can handle, it floods. The result can be sewage coming up in the yard or backing up into toilets and sinks.

What a pump tank is and why some homes have one

Not every yard is flat, and North Georgia has plenty of slopes. When the lay of the land or the soil calls for it, some systems add a pump tank, sometimes called a dose tank. It collects the liquid from the septic tank and sends it to the field in measured batches instead of a constant trickle. Spreading the flow out gives the soil time to absorb it.

A pump tank means a motor and floats that can wear out, and often an alarm. If you hear an alarm, read our page on a septic alarm going off. Systems with pumps or float switches are generally inspected more often than a simple gravity system.

How often a septic system needs attention

The EPA says to have a household septic system inspected at least every three years, and to have a household tank pumped every three to five years. The right timing depends on how many people live in the home, how much water you use, and the size of the tank.

A pro pumps the tank when the sludge and scum build up to a set level. One EPA marker is when sludge and scum make up more than 25 percent of the liquid depth in the tank. Keep every record, so the next person knows what was found.

Ryan does septic system repair and does not pump tanks, so for pumping you will call a septic pumping company. If an inspection shows something broken, that is where he comes in.

What makes a septic system fail

Most failures come from a few causes, and most are avoidable:

  • Too much water at once. The EPA notes that a single running toilet can add up to 200 gallons a day, and that doing all the laundry in one day can flood the drain field.
  • Solids and grease. Wipes, cooking grease and food scraps build up faster than the tank can handle. See what not to flush or pour down the drain on septic.
  • A tank that is never pumped. Once sludge reaches the outlet, solids head for the drain field.
  • Damage on top. Cars, trees and buildings over the drain field compact the soil or push roots into the pipes.
  • Failed parts. Broken baffles, cracked pipes, or a worn pump or float.

Signs your septic system needs help

Slow drains in every part of the house, gurgling sounds, a sewage smell, or very green, soggy grass over the field are all warning signs. If it is only one sink that is slow, it may be a simple clog. If every drain is slow at once, the problem is farther down the line. Our signs of a clogged main sewer line page covers the difference, and the sewage smell page covers odors.

A backup on a holiday weekend is no fun, and Ryan answers his own phone day and night. Text a photo of the alarm panel or the wet spot and he can tell you what to do next.

“The determination that Ryan displayed to get my septic system operational on a Sunday is just about unprecedented these days. Not afraid of hard work at a good price. Job two: Ryan installed a new bladder tank for my well. He showed up promptly and finished quickly at a better than fair price.”

Marty R., November 2024, Google review

Common Questions

Do all homes in North Georgia have septic?

No. Homes inside a city or county sewer service area use sewer. Many homes outside those areas use septic. Our guide on how to tell if you have septic or sewer shows you how to check.

How often should a septic tank be pumped?

The EPA says every three to five years for a household tank, with an inspection at least every three years. Your timing depends on tank size, household size and water use. A septic pumping company can tell you from what they see in the tank.

Does Ryan pump septic tanks?

No. Ryan repairs septic systems. For pumping, call a septic pumping company. If the tank, pipes or parts need repair, call or text Ryan for a free estimate.

What is the difference between the septic tank and the drain field?

The tank holds wastewater so solids settle and grease floats. The drain field is the buried pipework where the clear liquid soaks into the soil for final treatment.

Can I tell my septic system is failing before it backs up?

Often, yes. Slow drains in the whole house, gurgling, a sewage smell, and soggy ground over the tank or field are early signs. Call or text Ryan when you see them, before the backup.

Questions about your septic system?

Call or text Ryan. He is a licensed Master Plumber, and the estimate is free.

Call (706) 669-5727 Text Ryan