What is a Septic Tank: Complete Guide

Last Updated On May 24, 2024

Updated on September 14, 2022



Reviewed by

What is a Septic Tank Complete Guide

Are you buying a house that uses a septic tank, and want to know how it works? Or, do you already use a septic tank on your property but need to better understand it? You’re in the right place!

A septic system offers an eco-friendly waste management option that is really quite amazing. 

In this PlumbingNav guide, we will cover:

  • What is a septic tank?
  • What is the difference between a septic tank and a leach field?
  • What are the pros and cons of having a septic tank?

What's In This Guide?

      What is a Septic Tank?

      A septic tank is a physical tank (or tanks) buried in a private yard. More than 60 million Americans use a septic system. Some people install septic tanks by choice, while other geographic areas only have the option of using septic systems. 

      A septic system gives homeowners the ability to manage their own water waste instead of relying on (and paying) the local municipality. Having a septic system also reduces your water and sewer bill significantly. Furthermore, septic systems are actually better for the environment.

      did you know what is a septic tank

      What is a Septic Tank Used for?

      A septic tank treats wastewater on-site through either gravity fed or a pump-based system. 

      All waste or “sewage” that flows down your toilets and drains makes its way to your main line pipe. This “effluent” travels outside your home and ends up in your septic tank. The contents separate into three layers:

      • Scum and sludge
      • Liquid waste
      • Solid waste

      How does a septic tank system work?

      A conventional septic tank system treats the contents in the tank in different ways. 

      Waste “breaks down” in your septic tank, and about 60% of the solids are removed from the effluent before it is released back into the environment. The liquid effluent flows through the outlet pipe into the soil absorption area, also known as the drainfield (also referred to as a leach field).

      Waste water then empties out into the septic field and into the surrounding soil. The soil contains filtration properties that remove the toxins from the waste. Think of this process as a natural filter before the water finds its way back into the groundwater.

      Natural enzymes and bacteria help dissolve the accumulated solids that remain in the septic tank. Waste is contained and “digested” here, as it can’t get through the outlet pipe to the drain field

      Aerobic bacteria require oxygen, while anaerobic bacteria do not require oxygen. So, the anaerobic bacteria break down the solids in the tank while the aerobic bacteria kill the harmful waste in the soil prior to it reaching groundwater status. This is the natural process found in nature, and it’s pretty amazing.

      The remaining sludge layer accumulates in the septic tank until it’s full and gets pumped out by a professional every 3 – 5 years. However, you can gain more distance in between pumpings when using the best septic treatment products

      You’ll need to first locate your lid in order to check levels. Septic risers make it easy to inspect and access the septic tank for cleaning. Without regular pumping, you may experience the improper function of toilets, gurgling noises, plumbing backflow, or a potential costly backup. This may not be covered by your homeowner’s insurance policy if neglect is present.

      See the following video to learn more about how a septic tank works:

      Here is a nice brochure about septic systems that you can download from the EPA.

      What is a Septic Tank Made of?

      You can find septic tanks made from precast concrete or plastic. Concrete septic tanks weigh a lot. Furthermore, concrete tanks can crack and leak due to improper installation or settling. Plastic septic tanks consist of one molding, meaning they have fewer seams where a leak can form. Furthermore, plastic septic tanks don’t weigh as much, making them easier to install. 

      How Long Does a Septic Tank Last?

      A septic tank can last over 40 years when properly maintained.

      Proper maintenance starts inside the home. Don’t flush anything but human waste and the right type of toilet paper down the toilet. Furthermore, homeowners should not dispose of certain items down the garbage disposal.

      Items you should not allow into your septic system include:

      • Coffee Grounds
      • Grease, oil, and fat 
      • Bones
      • Egg Shells 
      • Wet-Strength Towels
      • Glass
      • Cat litter
      • Soil 
      • Fibrous Vegetables (ex. celery)
      • Facial Tissue
      • Q-tips, Cotton Balls
      • Tampons
      • Sanitary Napkins
      • Dental Floss
      • Condoms
      • Disposable Diapers
      • Hair 
      • Bandages
      • Cigarette Filters
      • Fabric
      • Flushable wipes

      Septic Tank Size

      Septic tanks come in different sizes based on the amount of wastewater created by the size of the household. 

      What is the standard size of a septic tank?

      See the following general guidelines for the right septic tank size and drain field size based on the number of people in the household:

      • 2 residents – 1000 – 1500 gallon tank and 800 – 2500 sq. ft. drain field
      • 3 residents – 1000 – 2000 gallon tank and 1000 – 2880 sq. ft. drain field
      • 4 residents – 1250 – 2500 gallon tank and 1200 – 3200 sq. ft. drain field
      • 5 residents – 1500 – 3000 gallon tank and 1600 – 3400 sq. ft. drain field
      • 6 residents – 1750 – 3500 gallon tank and 2000 – 3800 sq. ft. drain field

      What is the Difference between a Septic Tank and a Leach Field?

      The “septic tank” refers to the actual tank in your septic system. This is the area you will check sludge levels, accessible beneath a cover.

      The “leach field” refers to the perforated pipes that transport liquid effluent waste to the absorption field in your yard. The soil then treats the wastewater before it returns to the groundwater, assuming it “percs.”

      What Does Soil Perc Mean?

      This stands for the “percolation” rate and is a test to determine the water absorption rate of the soil. Soil must meet a minimum “perc test” in order to be permit approved and issued for drain field installation, or during building improvements. (Check with your local county as this varies.)

      What is the Main Purpose of a Septic Tank?

      The septic tank stores and treats wastewater. Inside the tank, enzymes and bacteria eat at the solid waste. Liquid waste effluent goes out to the drain field where it is absorbed back into the earth.

      What is the Main Purpose of a Leach Field?

      The leach field absorbs liquid effluent waste, where the soil naturally filters the contaminants using anaerobic bacteria before it returns to the clean groundwater.

      What are the Pros and Cons of Having a Septic Tank?

      Pros of having a septic tank

      There are numerous pros to having a septic tank. 

      First, septic systems save money. Homeowners save money on their sewer bill since they don’t need to pay the city for waste treatment services. Furthermore, the city saves money since they don’t need to install and maintain large-scale waste management infrastructure, including pipes and the treatment center itself.

      Second, you don’t need to rely on the city’s water treatment program, allowing for a more off-the-grid lifestyle.

      Third, septic tanks reduce your carbon footprint by naturally removing pollution from wastewater, recharging groundwater, and replenishing aquifers without the use of energy required at city stations. 

      Cons of having a septic tank

      There are some cons to having a septic tank as well. 

      First, septic tank owners retain all responsibility for maintenance, repairs, and replacement. Homeowners must take on the responsibility for not placing improper items down the drain, such as grease and oil. 

      The homeowner must also perform regular septic tank inspections and treatments. 

      Finally, if the septic tank requires replacement, the cost falls on the homeowner.

      Homeowners must learn about their plumbing system in more detail than otherwise required in order to treat the system properly. However, there isn’t a lot to it! 

      Septic Tank FAQ’s 

      What is the main purpose of the septic tank?

      Septic tank systems perform wastewater treatment of domestic sewage using natural processes.

      What are the pros and cons of having a septic tank?

      Pros include:

      • Lower monthly expenses
      • Independence
      • Eco-friendly

      Cons include:

      • Required in some areas, limiting options
      • The homeowner takes on financial responsibility for the septic system
      • Intermediate plumbing knowledge required

      Can toilet paper be flushed with a septic tank?

      You can flush toilet paper down a septic tank safely. Septic system manufactured design tanks to dissolve toilet paper and other paper material. However, sanitary products and diapers should go in the garbage and not into the septic tank.

      Meet Your Plumbing Navigator

      Plumbing Navigator: plumbing advice

      About Plumbing Navigator

      We’re passionate about all things plumbing, and love sharing tips, “how-to”, and reviewing the latest products to help make your project a success!

      Learn More Plumbing Tips

      Want to tackle more plumbing projects? Check out these helpful guides!

      best water heater stand
      tankless water heater flush kit
      best mesh drain strainer
      Best Shower Drain Cover

      Got Plumbing Questions? Search For In-Depth Answers Below!

      About Plumbing Navigator

      We write about "all things plumbing," helping you navigate common questions, repairs, and the best plumbing products on the market.

      About Plumbing Navigator

      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

      Recently Published Guides