What is a septic tank and how does it work?

Septic systems fulfill a crucial function for many homes and businesses that are in rural areas and homes in towns that have not gone to city water/sewer. Many people are not knowledgeable as to how a system works, and let’s face, why would they? As long as it’s doing it’s job, that’s all most homeowners care about. While septic tanks are usually low-maintenance systems, they can become tricky and expensive if something goes wrong. A basic knowledge is important to anyone wishing to avoid issues and problems with their system.

WHAT IS A SEPTIC SYSTEM?

Septic systems are basically small scale sewage treatment systems that are used in areas not connected to a sewage system operated by the government or a private company. They are often used by homes and farms in rural areas where it is too costly to connect to city sewage mains. Septic systems work by pumping waste water from the bathrooms, kitchens and laundry facilities into effluent tanks, which process the waste and then dispenses it into a septic drain field.

WHAT IS A SEPTIC TANK?

A septic tank is an important part of the septic system. It is essentially a water tank that holds between 4000-7500 liters of waste water. These typically get buried underground and are connected to an inlet pipe on one end (for sewage to flow in) and a septic drain field or “leach fields” on the other end (for filtered waste water to flow out). Modern septic tanks usually have two chambers, separated from each other by a dividing wall that has openings midway between the top and bottom of the tank.

WHAT HAPPENS IN A SEPTIC TANK?

First, the waste water enters the first chamber of the tank. The solids settle to the bottom, and scum floats to the top. Some of the solids at the bottom will decompose and float into the water. The liquid will move from the first to the second chamber via the openings in the dividing wall, leaving the solids and scum in the first chamber. In the second chamber, more settlement occurs. The liquid is now almost clear from the settlement process and drains from the tank to the septic drain field (also know as a leach field or a seepage field).

WHAT IS A SEPTIC DRAIN FIELD?

Septic drain fields are made up of trenches containing perforated pipes and some sort of porous material (like gravel). This is then covered by a layer of soil, which prevents animals from making contact with the waste water. The waste water is dispersed through the perforated pipes and runs through the gravel, which further removes contaminants and impurities. The purified water is introduced back into the environment through the roots of plants and evaporation.

WHAT POWERS A SEPTIC SYSTEM?

A septic system can run entirely on gravity, if the conditions are right. If the topography is not conducive to a gravity-powered septic system, a pump can be introduced.

WHAT HAPPENS TO WASTE THAT DOESN’T DECOMPOSE?

Some of the contents of the effluent tank will not decompose; therefore it is important to empty the tank occasionally. If tanks are not pumped the septic tank can fill with undecomposed substances that will be pumped into the drainage field. This can result in environmental problems as well as expensive repairs. How often the tank needs to be pumped clean varies depending on its size, the number of people using it and the outside temperature. Because there are so many variables, there is no rule of thumb for how often the tanks should be pumped. Some need it every few years while others can go between 10-20 years without pumping.

SOME FACTS FROM DHEC ABOUT SEPTIC SYSTEMS IN SOUTH CAROLINA

South Carolina households generate nearly 3 billion gallons of sewage each year. About 60 percent of homes are served by public or community sewer systems. The rest — more than 1 million households — rely on septic tanks located on their property.

Well designed, well-maintained septic tank systems use nature — bacteria and soil — to break down and filter the waste we flush and rinse away. They can be the safest, most cost-efficient way to treat  waste water.

But a leaky, clogged or damaged septic system can:

• Contaminate your home’s drinking water well and make your family and neighbors sick with diarrhea, nausea, cramps and hepatitis
• Push untreated sewage to the surface of your yard and into ditches and creeks
• Cause sewage backups in your sinks, tub and toilet
• Pollute nearby ponds, lakes and rivers, exposing people and animals to viruses and eye and ear infections, and
• Can be expensive to repair.

If you are experiencing a back-up or want your tank inspected, call a plumber today.