Water: Septic (Onsite / Decentralized) Systems
Frequently Asked Questions
Here are the most frequently asked questions and answers for the Decentralized (Septic) Program.
What are septic systems?
Septic systems are used to treat and dispose of relatively small volumes of wastewater, usually from houses and businesses that are located relatively close together. Septic systems are also called onsite wastewater treatment systems, decentralized wastewater treatment systems, on-lot systems, individual sewage disposal systems, cluster systems, package plants, and private sewage systems.
Why are these systems called "decentralized"?
They are considered decentralized because septic systems do not involve central wastewater collection and treatment.
The typical septic treatment system includes a septic tank, which digests organic matter and separates floatable matter (e.g., oils and grease) and settleable solids from the wastewater. Soil-based systems discharge the liquid (effluent) from the septic tank into a series of perforated pipes buried in a leach field, leaching chambers, or other special units designed to slowly release the effluent into the soil or surface water.
Alternative systems use pumps or gravity to help septic tank effluent trickle through sand, organic matter (e.g., peat, sawdust), constructed wetlands, or other media to remove or neutralize pollutants like disease-causing pathogens, nitrogen, phosphorus, and other contaminants. Some alternative systems are designed to evaporate wastewater or disinfect it before it is discharged to the soil or surface waters.
Most septic system failures are related to inappropriate design and poor maintenance. Some soil-based systems (with a leach or drain field) have been installed at sites with inadequate or inappropriate soils, excessive slopes or high ground water tables. These conditions can cause hydraulic failures and water resource contamination. Failure to perform routine maintenance, such as pumping the septic tank at least every 3 to 5 years, can cause solids in the tank to migrate into the drain field and clog the system.
Do not put the following items into sink drains or toilets: hair combings, coffee grounds, dental floss, disposable diapers, kitty litter, feminine hygiene products, cigarette butts, condoms, gauze bandages, fat, grease, oil, paper towels, paints, varnishes, thinners, waste oils, photographic solutions or pesticides.
If sewage from your plumbing fixtures or onsite system backs up into your basement, avoid contact with the sewage and the possibly harmful pathogens it might contain. Contact your local health department or regulatory agency. Cleanup personnel should wear protective clothing (e.g., long rubber gloves, face splash shields). After cleanup is complete, all equipment, tools, and clothing used in the cleanup and the flooded basement area should be washed thoroughly and disinfected with a mixture of 90 percent water and 10 percent household bleach. The area should be dried out with fans, heat lamps, or other devices and not be used until it has been completely dry for at least 24 hours. Additionally, click here for more information on what to do after flooding from a natural disaster event.
Septic Pages or the Septic Locator . These websites offer searchable databases of installers and septic system service providers. Contact a septic systems service provider or the National Association of Wastewater Transporters for more assistance.
The National Small Flows Clearinghouse has a Technical Assistance Hotline that can be accessed toll free at (800) 624-8301 or (304) 293-4191. You can also contact the Cooperative Extension Service Office nearest your home for information.
According to the U.S. Census Bureau, about 26 million homes (one-fourth of all homes) in America are served by decentralized wastewater treatment systems. The Census Bureau reports that the distribution and density of septic systems vary widely by region and state, from a high of about 55 percent in Vermont to a low of around 10 percent in California. The New England states have the highest proportion of homes served by septic systems: New Hampshire and Maine both report that about one-half of all homes are served by individual systems. More than one-third of the homes in the southeastern states depend on these systems, including approximately 48 percent in North Carolina and about 40 percent in both Kentucky and South Carolina. More than 60 million people in the nation are served by septic systems. About one-third of all new development is served by septic or other decentralized treatment systems.
Septic systems that are properly planned, designed, sited, installed, operated and maintained can provide excellent wastewater treatment. However, systems that are sited in densities that exceed the treatment capacity of regional soils and systems that are poorly designed, installed, operated or maintained can cause problems. The most serious documented problems involve contamination of surface waters and ground water with disease-causing pathogens and nitrates. Other problems include excessive nitrogen discharges to sensitive coastal waters and phosphorus pollution of inland surface waters, which increases algal growth and lowers dissolved oxygen levels. Contamination of important shellfish beds and swimming beaches by pathogens is also a concern in some coastal regions. EPA has developed Voluntary National Guidelines for Management of Onsite and Clustered (Decentralized) Wastewater Treatment Systems (PDF) (62 pp, 1MB, About PDF) to assist communities in establishing comprehensive management programs for septic wastewater systems to improve water quality and protect public health.
In most states, local health departments issue construction and operating permits to install septic systems under state laws that govern public health protection and abatement of public nuisances. Some states are beginning to add water resource protection provisions to their septic system regulations because of the possible impacts from nitrogen and phosphorus. Under most regulatory programs, the local permitting agency conducts a site assessment to determine whether the soils present can provide adequate treatment, to ensure that groundwater resources will not be threatened, and to stipulate appropriate setback distances from buildings, driveways, property lines and surface waters. Some states permit alternative systems if conventional soil-based systems are not allowable. Very few permitting agencies conduct regular inspections of septic systems after they are installed.
EPA is partnering with federal agencies, states, tribes, local governments and nongovernmental organizations to improve the management of septic systems. EPA's Guidelines for managing decentralized wastewater treatment systems can be tailored to meet the needs of states, counties, tribes, cities, towns, subdivisions and other areas where septic systems might threaten public health or water resources. The Voluntary National Guidelines focus on the following areas where better management can achieve significant improvements in overall system performance:
- Planning to ensure that system densities do not exceed the ability of regional soils and water resources to treat and assimilate pollutants;
- Site evaluations that characterize and help to protect soil, ground water, and surface water resources;
- System designs that provide predictable performance levels of treatment that are appropriate for protecting public health and the environment;
- Operation and maintenance procedures that ensure that systems are operated properly and that maintenance tasks (e.g., septic tank pumping, inspection of treatment units) are performed regularly;
- Monitoring and reporting to provide usable and easily accessible records on system inventories, capacity and performance; and
- Follow-up and corrective actions to ensure that failing systems are repaired, upgraded or replaced before public health or water resources are adversely affected.
The Voluntary National Guidelines are presented in the form of five model management programs. Each model program includes the elements and activities needed to achieve certain management objectives. The Voluntary National Guidelines address the sensitivity of the environment in the community and the complexity of the system used. The five model management programs are
- System Inventory and Awareness of Maintenance Needs
- Management Through Maintenance Contracts
- Management Through Operating Permits
- Responsible Management Entity (RME) Operation and Maintenance
- Responsible Management Entity (RME) Ownership and Management
No. The adoption of the guidelines is voluntary. EPA recognizes that states, tribes and local governments need a flexible framework so they can tailor their programs to the needs of the community. The guidelines are not intended to supersede existing federal, state, tribal, and local laws and regulations.
Septic systems serve approximately 25 percent of the U.S. population and about 40 percent of new developments. The U.S. Census Bureau has indicated that at least 10 percent of septic systems have stopped working. Some communities report failure rates as high as 70 percent! State agencies report that these failing systems are the third most common source of ground water contamination. In EPA's 1997 Response to Congress on Use of Decentralized Wastewater Treatment Systems (PDF) (101 pp, 5.8MB, About PDF), the Agency determined that with the technology now available, adequately managed decentralized systems can protect public health and the environment as well as provide long-term solutions for the nation's wastewater needs. The report also cited five major barriers to increasing the use of decentralized wastewater treatment systems, and one barrier is the lack of adequate management.
EPA's Office of Wastewater Management developed the Voluntary National Guidelines for Management of Onsite and Clustered (Decentralized) Wastewater Treatment Systems in cooperation with staff from the Office of Wetlands, Oceans and Watersheds; the Office of Ground Water and Drinking Water; the Office of Research and Development; EPA Regional offices; and the U.S. Department of Agriculture. Significant input was received from numerous stakeholders, state health agencies, environmental groups, and national organizations. See our partners page for a complete list.
The National Small Flows Clearinghouse has a Technical Assistance Hotline that can be accessed toll free at (800) 624-8301 or (304) 293-4191. The Rural Community Assistance Program provides assistance to communities having problems with their septic systems and can be reached at (888) 321-7227 or (202) 408-1273.