Types of Septic Systems

The most common type of septic system is the gravity-flow system. It relies on gravity to transport wastes from your home through the septic tank into the soil. The septic tank neutralizes the wastes with the aid of beneficial bacteria, and it is connected to perforated pipes that direct the neutralized waste into the soil below. Professional services can pump out your tank every two to three years to keep it clean and working smoothly.

In flatlands and other areas where the force of gravity is insufficient to send wastes into the soil without additional pressure, a chamber containing a pump is attached between your main drainpipe and the septic tank. This is called a pressure-distribution system, and it includes an electric pump between the septic tank and the drainage pipes that forces waste through the pipes when gravity is not sufficient to transport the waste. If your drainage pipes are buried beneath a raised mound of soil rather than underground, your septic system is referred to as a mound system. Yearly pumping and cleaning is recommended for both of these types of systems, as accumulated deposits can slow down or stop the action of the pump.

A sand-filter system adds a sand filter, which is basically a box filled with sand that is selected for its ability to filter impurities out of water, between the septic tank and pump chamber and the wastewater drainage pipes. There may be another pump installed between the sand filter and the drainage pumps, and it can be located in the sand-filter chamber itself. The sand filter helps to extend the life of your pump and prevent your tank from clogging by filtering out impurities before they can back up into your tank or pump chamber. Annual maintenance is also recommended for sand-filter systems.

Aerobic-treatment units force air into an aeration chamber, which allows bacteria that digest the waste to grow and reproduce by absorbing the nutrients in the waste. Some systems of this type also use an auxiliary chamber which collects solids that are difficult for the bacteria to digest quickly. The solids are then broken up and forced back into the first chamber where they eventually decompose before traveling through the drainage pipes as treated wastewater. These complex systems require service contracts and monitoring according to state and local laws in most jurisdictions. You may be required to install this type of system if the water table is too high for a regular septic tank system to function.