centralized sewerage system, building moratoriums and limitations on the subdivision of property are often imposed. ensuring existing septic tanks are functioning properly can also be helpful for a limited time, but becomes less effective as a primary remediation strategy as population density increases. surface water pollution in areas adjacent to water bodies with fish or shellfish intended for human consumption, improperly maintained and failing septic systems contribute to pollution levels that can force harvest restrictions and/or commercial or recreational harvest closures. use in the united states, the 2007 american housing survey indicated that about 20 percent of all households rely on septic tanks, and that the overwhelming majority of systems are located in rural (50%) and suburban (47%) areas. indianapolis is one example of a large city where many of the city's neighborhoods still rely on separate septic systems. in europe, septic systems are generally limited to rural areas. regulations european union in the european union the en 12566 standard provides the general requirements for packaged and site assembled treatment plants used for domestic wastewater treatment. part 1 (en 12566-1) is for septic tanks that are prefabricated or factory manufactured and made of polyethylene, glass reinforced polyester, polypropylene, pvc-u, steel or concrete. part 4 (en 12566-4) regulates septic tanks that are assembled on site from prefabricated kits, generally of concrete construction. certified septic tanks of both types must pass a standardized hydraulic test to assess their ability to retain suspended solids within the system. additionally, their structural adequacy in relevant ground conditions is assessed in terms of water-tightness, treatment efficiency, and structural behaviour. france in france, about 4 million households (or 20% of the population) are using on-site wastewater disposal systems (l’assainissement non collectif), including septic tanks (fosse septique). the legal framework for regulating the construction and maintenance of septic systems was introduced in 1992 and updated in 2009 and 2012 with the intent to establish the technical requirements applicable to individual sewerage systems. septic tanks in france are subject to inspection by spanc (service public d’assainissement non collectif), a professional body appointed by the respective local authorities to enforce wastewater collection laws, at least once in four years. following the introduction of en 12566, the discharge of effluent directly into ditches or watercourses is prohibited, unless the effluent meets prescribed standards. ireland according to the census of ireland 2011, 27.5% of irish households (i.e. about 440,000 households), with the majority in rural areas, use an individual septic tank. following a european court of justice judgment made against ireland in 2009 that deemed the country non-compliant with the waste framework directive in relation to domestic wastewaters disposed of in the countryside, the water services (amendment) act 2012 was passed in order to regulate wastewater discharges from domestic sources that are not connected to the public sewer network and to provide arrangements for registration and inspection of existing individual domestic wastewater treatment systems. additionally, a code of practice has been developed by the environmental protection agency to regulate the planning and construction of new septic tanks, secondary treatment systems, septic drain fields and filter systems. direct discharge of septic tank effluent into groundwater is prohibited in ireland, while the indirect discharge via unsaturated subsoil into groundwater, e.g. by means of a septic drain field, or the direct discharge into surface water is permissible in accordance with a water pollution act license. registered septic tanks must be desludged by an authorized contractor at least once a year; the removed fecal sludge is disposed of, either to a managed municipal wastewater treatment facility or to agriculture provided that nutrient management regulations are met. united kingdom since 2015, only certain property owners in england and wales with septic tanks or small packaged sewage treatment systems need to register their systems, and either apply for a permit or qualify for an exemption with the environment agency. permits need to be granted to systems that discharge more than a certain volume of effluent in a given time or that discharge effluent directly into sensitive areas (e.g., some groundwater protection zones). in general, permits are not granted for new septic tanks that discharge directly into surface waters. a septic tank discharging into a watercourse must be replaced or upgraded by 1 january 2020 to a sewage treatment plant (also called an onsite sewage facility), or sooner if the property is sold before this date, or if the environment agency (ea) finds that it is causing pollution. in northern ireland, the department of the environment must give permission for all wastewater discharges where it is proposed that the discharge will go to a waterway or soil infiltration system. the discharge consent will outline conditions relating to the quality and quantity of the discharge in order to ensure the receiving waterway or the underground aquifer can absorb the discharge. the water environment regulations 2011 regulate the registration of septic tank systems in scotland. proof of registration is required when new properties are being developed or existing properties change ownership. australia in australia, septic tank design and installation requirements are regulated by state governments, through departments of health and environmental protection agencies. regulation may include codes of practice and legislation. regulatory requirements for the design and installation of septic tanks commonly references australian standards (1547 and 1546). capacity requirements for septic tanks may be outlined within codes of practice, and can vary between states. mainly because of water leaching from the effluent drains of a lot of closely spaced septic systems, many council districts (e.g. sunshine coast, queensland) have banned septic systems, and require them to be replaced with much more expensive small-scale sewage treatment systems that actively pump air into the tank, producing an aerobic environment. septic systems have to be replaced as part of any new building applications, regardless of how well the old system performed. united states according to the us environmental protection agency, in the united states it is the home owners' responsibility to maintain their septic systems. anyone who ignores this requirement will eventually experience costly repairs when solids escape the tank and clog the clarified liquid effluent disposal system. in washington, for example, a "shellfish protection district" or "clean water district" is a geographic service area designated by a county to protect water quality and tideland resources. the district provides a mechanism to generate local funds for water quality services to control non-point sources of pollution, such as septic system maintenance. the district also serves as an educational resource, calling attention to the pollution sources that threaten shellfish growing waters. slang usage the term "septic tank", or more usually "septic", is used in britain and australia as a slang term to refer to americans, from cockney rhyming slang septic tank = yank. this is sometimes further shortened to "seppo".