Domestic sewage from toilets and wastewater from sinks, showers and washing machines flow into the septic tank. Heavier solid matter sinks to the bottom of the septic tank and forms sludge, while lighter materials like fats, oils and greases float to the top and form scum.

Effluent water exits the septic tank through perforated pipes into a constructed absorption or “leach” field. Bacteria in the leach field further break down any residual pollutants. Contact The Septic Guys for professional help.
A septic tank is a system for treating wastewater on your property, usually in rural areas where you’re not connected to the main sewage network. It’s made up of a series of components that collect and retain household sewage, remove wastewater pollutants, and return the treated effluent to your soil or environment via infiltration.
Wastewater from your toilets (called black water) and from your kitchen sinks, bathtubs, laundry machines, and dishwashers flows into the septic tank. Heavier solid matter sinks to the bottom of the tank and forms sludge, while lighter matters such as fats, oils, and greases float to the top and form scum. Anaerobic organisms in the septic tank break down these organic wastewater pollutants, converting them to inert matter. This process is very slow and can only be done by a combination of biological and mechanical processes.
When the septic tank is full, it will discharge into a perforated pipe that leads to an absorption field, also called a lateral field or drain field. The partially-treated wastewater flows into this area, where it’s absorbed into the soil and groundwater by microorganisms in the gravel and grass above.
Some septic tanks may also have an effluent filter, which is a device that reduces concentrations of organic materials, suspended solids, pathogens, and nutrients like phosphorus or nitrogen. If your septic tank has an effluent filter, it’ll need to be regularly cleaned, ideally when you have the tank desludged.
A septic system should always have a vent stack. It’s important to ensure that the system is properly vented so that gases can escape, which prevents them from contaminating the surrounding environment or causing problems with your home plumbing.
A septic system needs regular maintenance, including pumping and inspections. Pumping is important, because the septic tank fills up with sludge and scum over time, which can then leak out of the tank into the absorption field. This can be messy and costly, so you should have your septic tank pumped on a regular basis. It’s recommended to have your septic tank pumped twice over 2 or 4 years, with sludge level measurements taken so that you can determine how often your septic system needs to be pumped.
How Does a Septic Tank Work?
Wastewater from toilets (called black water) and drains from your kitchen, bathtub, sink, washing machine and dishwasher (called grey water) run through a main drainage pipe to your septic tank. Solid materials in the wastewater like hair, soap scum, fats and oils sink to the bottom of your septic tank and form sludge. Liquid wastewater passes through an effluent filter near the septic tank outlet and is pushed to your septic system’s drain field by gravity.
A baffle wall, sometimes called a partition wall or divider wall, directs the incoming raw sewage downward to the mid-level of your septic tank. This design keeps surface scum from entering the septic tank and reduces wastewater agitation, which makes it easier for solids to settle on the bottom of your septic tank.
As wastewater flows into your septic tank, bacteria inside the septic tank begin to break down these organic wastewater pollutants. Some of this breakdown occurs in the sludge layer at the bottom of your septic tank while other bacteria (anaerobic) in the scum layer at the top of your septic tank feed on fatty acids and other floating debris. The resulting liquid wastewater, called effluent, exits the septic tank into your septic system’s drain field where soil bacteria and sand filtration finish the treatment process.
If too much sludge or scum accumulates in your septic tank, it will overflow into the drainage field and cause the sewage to seep out onto the ground surface where it exposes people and pets to disease-causing organisms. This is why it’s important to have your septic tank pumped regularly.
You may have seen hardware stores selling septic tank additives that claim to provide additional bacterial activity or promote faster septic tank emptying. However, these bacterial spores need oxygen to grow and are typically used in conjunction with other tank cleaning products. Adding them on their own will only delay your septic tank pumping. You should also avoid flushing anything other than toilet paper and human waste into your septic tank. Items that you flush down the drain like handi-wipes, grease, oil, paper towel and feminine hygiene products can clog the pipes that lead from your septic tank to your septic system’s leach field.
What is a Septic System?
A septic system is an on-site wastewater treatment and disposal system used to manage waste from household plumbing like toilets, kitchen drains, laundry, and more. It uses natural processes and technology to purify wastewater and drive it into the soil for absorption. Almost one in five homes in the US is on its own septic tank instead of connected to the public sewer.
A Septic System contains a series of components including a septic tank, an absorption field or leach field, and a sand filter. A septic system must be located on a site with adequate depth and suitability of soil to effectively treat the wastewater.
Wastewater enters the septic tank through an inlet pipe and is kept there until bacteria decompose some of the waste materials. Heavy solids, such as feces and toilet paper, will settle to the bottom layer in the septic tank called sludge. Oils and grease float to the top and form a layer called scum. The liquid portion of the wastewater flows through a perforated outlet that should have a screen or filter to block large debris.
Once the septic tank is full, it is pumped out to the distribution box via the inlet and outlet pipes. The distribution box is a small, round or rectangular watertight container made of concrete or plastic that sits underground. It is connected to the outlet pipe on the septic tank on one end and a series of pipes leading to the drain field on the other end. The distribution box’s role is to receive the septic tank effluent and evenly distribute it into the pipes that disperse it in the drain field. Uniformly distributed wastewater ensures the drain field works effectively and prevents one area from becoming overloaded with sewage.
An effluent filter is a device that sifts out the remaining waste materials, allowing the bacterial process to finish breaking down harmful pollutants. A septic tank with an effluent filter requires regular cleaning. Depending on the size of your septic system and how much you use it, you may need to clean your effluent filter every time your septic tank is emptied (desludged). If not cleaned regularly, the filter could clog and allow sewage to enter the home or yard.
How do I Maintain a Septic System?
The wastewater that flows from your home’s toilets, showers and sinks goes down a drain and into the main pipe that leads to your septic tank. The septic tank is typically a large concrete box. Heavier solid waste sinks to the bottom of the tank to form sludge while oils and greases float to the top of the tank to form scum. Bacteria inside your septic system decompose the sludge and scum into inert matter that can pass through the outlet of the septic tank.
When the septic tank is full, it must be pumped out. You can extend the life of your septic tank and system by limiting what is poured into it, including kitchen, bath and laundry products.
It is also important to have your septic tank inspected by a professional and pumped out as needed. Your septic technician can check for baffles that may be missing or broken which can lead to clogs.
Keeping an accurate maintenance record for your septic tank, including dates of pumping and inspections is crucial. This will help you avoid problems, such as the awful odors that can occur from a failing septic system. This record will also come in handy if you decide to sell your home in the future as it can show prospective buyers what has been done to keep the septic system in good working order.
A properly functioning septic system can protect your family’s health and the environment. However, septic systems that are not well-maintained or are failing can contaminate nearby drinking water wells and surface water bodies. The pathogenic bacteria and viruses that septic systems can release into waterbodies can cause illness in humans and animals. Excess nutrients from septic systems can also lead to harmful algal blooms that use up oxygen in water, threatening fish and other aquatic life.
Some simple steps can greatly improve the condition of your septic system and prevent it from needing to be pumped or replaced. Do not flush items that do not break down, such as feminine hygiene products, paper towels, cigarette butts, dental floss and cat litter. These items can enter the septic tank and clog it or the lateral field and cause wastewater to seep into the groundwater.