When someone purchases a home that includes a septic tank and drainfield instead of a connection to a paid sewer system, they often have questions about the workings of the tank. Since the discussion of septic tanks is not always deemed appropriate over lunch with friends or coworkers, good questions can go unanswered. If you are the proud new owner of a home and the septic system that serves it, this information will offer you answers to questions you might not have been able to ask.
The septic tank
Septic tanks are constructed from many different materials, including metal, concrete, fiberglass, or a plastic-like poly material, and can be box-like, spherical, or somewhat barrel-shaped in design. They are made to be watertight so that raw, unprocessed sewage inside does not leak out into the soil surrounding the tank and endanger groundwater supplies or cause contamination issues.
As the wastewater and solids are moved from the home and through the drain pipe and then deposited into the septic tank, three distinct layers will form. Bacterial colonies inside the tank help to digest this waste matter and keep it moving through the system.
The scum layer
The top layer forms from waste deposited inside the tank and is called scum. The scum layer is made up of solid materials that tend to float on top of water, like grease, oil, and soap suds.
The second layer is the largest and it is made up of gray water from bathing, laundry, and washing dishes, as well as what is known as black water, which is the urine, liquefied feces, and accompanying water that comes from flushing the toilet. Effluent is drained from this layer through a baffled valve system that pushes it to the drainfield to complete the process by slowly dispersing it into the soil.
The sludge layer
On the bottom of the septic tank is the sludge layer, which grows slowly over time. This layer is composed of human feces and any solid matter that cannot be processed by the bacterial action of the septic tank. If the sludge layer grows too large, there will be no room for wastewater to be processed into effluent and the septic system can become overloaded.
Now that you know more about how your septic tank actually functions, you can understand the need to keep the system healthy by having some of the volume removed from the septic tank on a periodic basis. A septic tank service contractor can help you determine how often your tank will need to be pumped and how much waste volume should be removed during each service visit.