How Does a Septic Tank Work? The Pumping and Removal Process

Municipal sewage processing is a modern marvel: You simply flush the toilet, and everything disappears! The process is a little more complicated if you have a septic system. Exactly how does a septic tank work, and how do you maintain one? 

An informed septic tank user can make better decisions when faced with a septic system problem, so here we’ll answer your most pressing questions about septic tanks, how they work, and why they need regular professional attention. 

What Is a Septic Tank?

A septic tank is an underground, watertight container that's part of a larger wastewater treatment system called a septic system. Solids in wastewater settle in the tank, where bacteria break them down. Treated liquid discharges into a nearby drain field. Septic tanks are used in areas without access to public sewer systems. 

How deep are septic tanks buried?

A septic tank is buried four inches to four feet below ground, depending on the lowest point of your outgoing sewer line, local terrain, and the depth of the water table. 

Mechanics of a Septic System

Your septic tank is divided into four major parts:

• The sewer drain carries waste from your home to the septic tank.
• The septic tank collects the waste. Septic tanks are watertight and typically buried below ground. Normally, all you’ll see of the tank are the inspection pipe and access covers. 
• The effluent drain pipe carries partially treated water from the tank to the drain field where it is dispersed into the soil. 
• The drain field is a system of perforated pipes buried a few feet in the soil. 

How a Septic Tank Works: Step-by-Step

1. Wastewater enters the tank

Your home produces wastewater from toilets, showers, sinks, and washing machines. Your home’s plumbing directs wastewater to a main drainage pipe that moves wastewater into the septic tank.

2. Solids settle to the bottom of the tank

Solids in wastewater sink to the bottom of the tank. Oils and grease float to the top of the tank, with a layer of liquid separating the grease from the solids. Bacteria in the tank get to work, breaking down solid organic matter into a thick sludge. 

3. Partial water treatment occurs

As the bacteria get to work, the liquid water forms a partially treated effluent. 

4. Effluent Discharge

Once partially treated, the effluent leaves the septic tank through an outlet pipe and flows into the drain field.  

5. Effluent filters through the drain field. 

In the drain field, the effluent moves through perforated pipes and into surrounding gravel and soil, which provides natural filtration. Eventually, the filtered effluent reaches the groundwater table, where it returns to the water cycle. 

The Role of the Drain Field

The effluent that enters the drain field contains germs that pose a health hazard to humans and animals. The soil collects these impurities, and then systematically filters and kills them.

Signs of Septic System Problems

Septic tanks are complex systems and can malfunction. You may have a problem with your system if you encounter any of the following signs:

• Wastewater and sewage back up in toilets, sinks, showers, and tubs. 
• Slow drainage in tubs, showers, and sinks. 
• Gurgling sounds from drains or pipes. 
• Standing water or persistent damp spots near the septic tank or drain field. 
• Foul smells from the drain field, septic tank, or indoor drains. 
• Green, lush, and spongy grass or other vegetation over the septic tank or drain field, even in dry conditions.
• High levels of nitrates or coliform bacteria are detected in nearby water wells.
• Algal blooms in nearby ponds or lakes.

Many systems have built-in alarms that alert you to issues with your septic system.   

How to Care for Your Septic System

It is important not to flush kitchen grease, solid waste, or petroleum products into the septic system. These products inhibit bacteria’s ability to break down raw sewage. Enzymes or other retail chemical cleaners should not enter the septic system. Vehicles should not drive over the tank or drain field, as they can damage the system. 

You can grow grass and shallow-rooted plants over the drain field. However, avoid planting deep-rooted trees, as their roots can inhibit the natural processing of the effluent.

How do you know when your septic tank is full?

If you detect any of the signs mentioned above, you may need to have your septic tank emptied. Otherwise, a correctly installed septic system should be able to go two or three years before needing to be pumped. Select Roto-Rooter locations can pump the tank to remove the buildup of solids. However, this is not offered in all markets, and Roto-Rooter may refer you to a partner local pumping company. 

How long do septic tanks last?

A septic tank can last 20 to 40 years or more with proper care. 

When to Call a Professional

Contact a professional plumber if you detect signs of a septic sewer problem. Even minor septic tank issues need immediate attention, as they can quickly deteriorate into serious problems. As the septic tank is a sewage repository, it contains potentially dangerous germs and bacteria. Roto-Rooter plumbers have the training to work safely with septic tanks and have the professional equipment needed to fix problems quickly and empty full tanks. Contact us, and we’ll help keep your septic system working at peak efficiency!