Conventional Gravity-Flow Septic System

Different types of septic systems exist to fit various soil and site conditions. A conventional gravity-flow septic system consists of three main components: a septic tank, the drainfield with its replacement area, and the surrounding soil. Understanding how these components work together is key to ensuring effective operation at the lowest cost possible.

What is a Septic Tank?

A septic tank is a large, buried container made out of concrete, fiberglass, or polyethylene that is used to treat and store wastewater from toilets, showers, kitchen sinks, and other household appliances. Wastewater flows into the tank and heavy solids settle to the bottom where bacterial action decomposes them. Oil and grease accumulate at the top of the tank and form a scum layer.

Septic tanks are typically two compartments with inlet and outlet tees that slow incoming sewage and prevent solids from entering the drainfield. To ensure optimal performance, they need to be pumped every 3-5 years depending on how much wastewater enters it.

Although some products claim to improve performance, they are usually not necessary or recommended as they can cause early soil clogging in the drainfield. The effluent leaving a septic tank still contains bacteria and pollutants so it must not be discharged onto the ground surface or into surface or groundwater as it is illegal.



The drainfield plays an important role for septic tanks. It is usually made up of a series of trenches or beds and contains perforated pipes that direct the wastewater slowly through either gravel-filled or gravelless trenches, and into the soil beneath. The exact size and type of system depends on the type of soil it’s installed in, as well as the amount of wastewater produced on a daily basis.

To ensure there is space to conduct repairs when needed, every new drainfield must be accompanied by a designated 100% replacement area which needs to remain free of any damage or encroachment.


The Soil

The soil is an important part of the septic system, providing filtration and treatment of the waste effluent from the tank. As effluent passes through the soil’s pore spaces it is chemically and biologically treated before entering either the groundwater or another restriction layer such as hardpan, bedrock, or clay soils. The best environment for treating this effluent is a well-drained soil that remains unsaturated with plenty of oxygen present in the lower layers several feet underneath the drainfield.

Septic Tank Failure Warning Signs

Are you worried that your septic system might be failing? Watch out for these warning signs: foul odors, sewage surfacing or wet spots in the drainfield area, plumbing or septic tank backups, slow draining fixtures, or gurgling sounds. If you notice any of these issues, contact your local health agency right away!

10 Tips for Taking Care of Your Septic Tank


  1. Accurate records should be kept of the location, size, and maintenance of your septic system. A simple diagram will do and can be obtained from the local health agency if necessary. Keeping track of maintenance done on the system is especially important, as these notes will be beneficial for future generations inhabiting your home or for when problems arise.
  2. To ensure your septic system is functioning well and avoiding early warning signs of possible breakdown, it’s important to regularly inspect your septic tank. This should be done at least once a year. Inspect the sludge and scum levels inside the septic tank to ensure that the layers of solids are not too high. Also check for any battered or tee fittings as well as both downslope and drainfield areas for any odors, wastewater, or sewage surfacing. Check monitored pipes to make sure liquid levels remain around 6 inches or lower. Keeping on top of regular maintenance checks can help you spot any potential problems quickly and prevent further damage from occurring.
  3. To avoid disastrous problems like clogging of the drainfield and sewage back-up into the home, it is recommended that you regularly pump out your septic tank. Especially if you are using a garbage disposal which increases the amount of solids entering the septic tank, more frequent pumping will be necessary. Don’t wait until you notice a problem – maintain your septic tank through routine pumping as necessary.
  4. It is important to never flush any materials that can be harmful for the septic tank down the toilet or drains. These materials include grease, cooking oils, newspaper, paper towels, rags, coffee grounds, feminine hygiene products, diapers, and flushable wipes. Furthermore, avoid introducing chemicals such as solvents, oils paint or pesticides into the system as they are all detrimental to its proper operation and may even pollute ground water. Finally, septic tank additives are not recommended, and no additional additives are needed for its proper functioning.
  5. Keeping runoff away from your septic system is important in order to maintain its proper functioning. To do this, ensure that water from surfaces like roofs, driveways, and patios are flowed away from the tank and drainfield. Additionally, make sure to slightly mound soils over your system to prevent flooding of the area with surface runoff.
  6. To keep your system in good condition, don’t let traffic such as vehicles, heavy equipment, or livestock near your drainfield or replacement area. The pressure can cause compaction of the soil and damage pipes. Additionally, if you plan to plant a garden, construct a building, or install a pool, be sure to first check for the location of your system and replacement area so that there are no surprises down the line.
  7. Ensure your septic system is landscaped properly by avoiding the use of impermeable materials, such as concrete or plastic, over the drainfield or replacement site. These materials can obstruct air supply to the soil, hinder access to the system for maintenance and repair, and reduce evaporation needed for effective treatment. The best cover material is grass.
  8. Under no circumstances should anyone ever enter a septic tank. Dangerous gases, such as poisonous oxygen-deprived fumes, can be extremely hazardous or even fatal in these confined spaces. Therefore, all maintenance to septic tanks should be carried out externally by professionals.
  9. If your septic system is experiencing any issues, it’s important to reach out to your local health agency for help. Many troubles can be resolved with minimal effort and expense, while other more serious issues may require a complete drainfield replacement.
  10. Practicing water conservation can extend the life of your drainfield and avoid costly repairs. To reduce your water use, look for water-saving devices, repair leaky faucets and plumbing fixtures, and reduce toilet reservoir volume or flow. You should also try to take shorter showers, bathe with partially filled tubs, and wash only full loads of dishes and laundry. All these simple changes can make a big difference in how much water you use!