All plumbing from a home with a septic system converges into a sizable underground container called a septic tank. This water-tight tank is buried in the soil with only inspection ports and access ports visible.
In the septic tank, bacteria break down solids in wastewater. This allows a percentage of the liquid to flow out into the soil absorption field.
What is a septic tank?
The septic tank is a watertight container usually made of concrete or fiberglass that holds wastewater from your home. Its purpose is to keep waste in a contained location until microorganisms can break it down and return clean water to the environment.
The tank is a buried, rectangular tank with an inlet wastewater pipe and an outlet drainage pipe. The inlet and outlet tees are positioned below the surface of the wastewater layer so that hydraulic pressure will push the wastewater through the inlet tee to the drain field when you flush or use water in your house. This is what keeps the solids in your septic tank in the sludge layer and prevents them from flowing out into your absorption field and damaging your system.
After wastewater enters the septic tank, weighty masses such as sewage, sludge, oil, and grease sink to the bottom of the tank, where they decompose. Less dense masses, such as scum, rise to the surface of the wastewater and come into contact with the bacteria that live in your septic tank. These microorganisms break down the scum and sludge into liquid effluent, which is the wastewater that exits your septic tank through the outlet pipe and travels to your septic drain field.
Once the wastewater leaves your septic tank, it moves through the inlet and outlet tees and into an absorption field or drain field, which is a series of trenches filled with washed gravel, stone or a gravelless product where the wastewater is biologically treated by the soil that surrounds it. It is important to plant grass and other shallow-rooted plants over the absorption field and keep trees, shrubs, and long-rooted grass away from it so that they do not grow into and clog your drain field pipes.
Some septic tanks have an inlet baffle, an outlet cover to limit the amount of waste entering the tank, and a distribution box and a grease trap. While not found on all systems, these items are an excellent way to prolong the life of your septic system and ensure that your wastewater is properly treated.
What is a drain field?
The liquid waste that leaves your septic tank (called effluent) travels to the drain field, also known as an absorption field or leach field. The soil in your drain field treats the wastewater by absorbing it and killing bacteria and microorganisms. When your septic system is functioning properly, the drain field removes all disease-causing solids from the sewage, making it safe for the environment.
When the wastewater enters the drain field, it travels through perforated pipes buried underneath the ground. The soil in the drain field filters and breaks down the sewage, further treating it as it percolates through the ground. Over time, the soil in your drain field eliminates most of the bacterial and chemical pollutants.
Once the sewage has been filtered through the perforated pipe network in the drain field, it will seep into a layer of gravel, where the final treatment occurs. Depending on the type of soil in your drain field, it may treat the wastewater by absorbing it into the ground or through evaporation into the air.
The soil in your drain field is essential to a properly functioning septic system because it absorbs and breaks down the organic waste from the septic tank and household plumbing fixtures. However, if there is too much wastewater in the drain field, it can overflow and cause a sewer backup.
This is why performing regular septic system maintenance is important and keeping the amount of waste you dump into your septic tank below its capacity. Too much waste will force the partially treated wastewater into your drain field and cause it to overflow, damaging the surrounding soil and clogging toilets and faucets.
Over time, the septic system components that work together to treat your wastewater can become damaged by tree roots, excessive weight on the septic tank and drainage field, improper soil grade, and other factors. If your septic system begins to fail, it is important to have it inspected and serviced to ensure the proper function of the septic tank, drain field, and distribution box.
What is a distribution box?
While most homeowners know to get their septic tank pumped every two to five years, there’s much more to a septic system than just the tank. A septic distribution box, also known as a d-box, is one of the most important parts of a septic system. Its job is to evenly distribute wastewater into a drain field.
Without a d-box, wastewater would flow straight from the septic tank into a drain field without any balancing or treatment. This would cause the drain field to become overloaded and clogged. Instead, the d-box, which looks like a concrete box with a lid, is fitted with perforated pipes that lead into the leach field. Its openings are often fitted with flow leveling devices that rotate to ensure that all leach field lines receive equal amounts of wastewater.
A septic distribution box is typically located between the septic tank and the drain field, although some systems use a septic tank bypass that does not have a distribution box. A septic tank distribution box can be made of fiberglass, plastic, or concrete and can vary in size depending on the number of drain fields and household sewage output. Ideally, a distribution box should be placed in a location where it is easy to access. It should also be buried at the same depth as the septic tank.
Several types of septic tank distribution boxes exist, including parallel and serial distribution systems. A parallel septic tank distribution system has multiple underground lines that carry sewage to the drain field. A serial septic tank distribution system involves a watertight pipe from the septic tank to the first trench, where it ponds until it reaches capacity. Then, it is delivered to the next trench, and so on.
If a septic tank or d-box is not properly installed or maintained, it can break down, leak, or even overflow into a leach field. To avoid this, it is recommended that a professional septic tank installation company be used. The septic tank and d-box will be inspected regularly for any repairs or replacements needed.
When should I pump my septic tank?
If you live in the country, away from municipal sewer systems, your septic system is how you take care of waste. It consists of the septic tank, drain field, and distribution box. These parts work together to filter your home’s wastewater and keep it from seeping into groundwater. Keeping your septic tank system working properly requires routine inspections and periodic pumping.
Your septic tank is a watertight container that’s usually buried underground. It’s typically made of fiberglass or concrete. The tank is sized to hold all the wastewater that enters your house from one or more main drainage pipes. As the waste is absorbed, solids sink to the bottom, forming a sludge layer. Oils and fats float to the top and form a scum layer. The top layer of water exits your leach field. The bottom sludge layer is decomposed by bacteria and eventually seeps into the soil. Your septic tank needs to be pumped when the sludge and scum layers are at or near the outlet port. A professional technician will use a special sensor to determine how full the tank is.
A septic tank should never be treated like a trash can. Only human poop and pee, toilet paper, and non-flushable cleaning and laundry products should go down the drain. Other materials can clog your septic tank or the absorption field. These include baby wipes, cleaning wipes, and moist towelettes; feminine hygiene products, including tampons and pads; household chemicals such as paint thinner, polyurethane, and pesticides; and solvents such as acetone and gasoline. These substances can kill the bacteria in your septic tank, poison the environment, and pollute groundwater.
Avoiding these items can prolong the life of your septic tank and help reduce the need for frequent pumping. It’s also a good idea to limit or eliminate the use of garbage disposal. Food waste can also fill the septic tank and cause a clog in the drain field.
Some people buy septic tank additives that claim to slow down the rate at which sludge and scum build-up. However, these additives aren’t necessary to keep your septic tank running well, and they don’t prevent the need for regular pumping.
