sealPurdue News

April 12, 2002

Down the drain: Hoosier septic systems shouldn't be left behind

WEST LAFAYETTE, Ind. – Once wastewater is flushed from homes into septic tanks it is easily forgotten. However, two Purdue University soil scientists say homeowners should be more concerned about what washes down the drain.

"Most homes and many larger buildings depend on a septic tank and a soil absorption field to get rid of sewage," says Donald Franzmeier, Purdue agronomy professor. "On-site wastewater disposal systems that function properly contribute very little to water pollution. However, when these on-site systems fail, they may cause health hazards, contaminate groundwater and surface water, and transmit diseases."

Franzmeier says 25 million homes in the United States and one-third of Indiana homes rely on septic systems. Close to 15,000 new systems are installed each year in Indiana and thousands are repaired, he says.

When old systems are repaired or new systems are constructed, it is important to have reliable soil information, Franzmeier says. Soil characteristics largely determine if septic systems and soil absorption fields are suitable for an area.

Well drained soils that have moderate permeability and are located in sloping areas are best for septic systems, Franzmeier says. Many Indiana soils drain poorly and are not suitable to disperse effluent, or liquid material from waste treatment, through the soil absorption field.

Septic systems should be designed and installed with different soil types in mind, he says. Homeowners should be aware of soil types around their homes and how the soils drain. This will enable them to look for potential septic system problems.

Septic systems can fail in three ways. One sign of a possible failure is when water does not go down the drain or flush from toilets properly. Homeowners also may notice ponding or standing water on the surface of their lawn above the absorption field, which indicates the soil is not absorbing the effluent as fast as it is produced. The system also may seem to be functioning, but the effluent may not be properly purified through the system and can cause contamination in groundwater supplies and waterways.

"Successful on-site sewage treatment requires quality soil investigation, good design, careful installation and regular maintenance," Franzmeier says. "If any of the four links in this chain is weak, the system may fail."

Purdue scientists are studying septic systems in the state.

Brad Lee, assistant agronomy professor, and Heidi Stout, agronomy graduate student, are looking at the repair and replacement rates of Tippecanoe County septic systems. They are working with the Tippecanoe County Board of Health to better understand why septic systems fail and what is the average life span of a septic system.

Throughout the state, Purdue Extension also is working with county plan commissioners, the Indiana State Department of Health, Indiana Rural Community Assistance Program and Indiana Onsite Wastewater Professional Association on septic system issues. These groups are working together to build a statewide organization that emphasizes maintenance, training and proper installation of on-site systems, says Don Jones, Purdue agricultural engineer.

The state also passed a law in 2001 that established registration for soil consultants, or those who evaluate soils and landscapes for septic systems. The program, known as the Indiana Registry of Soil Scientists, is administered by a board appointed by Gov. Frank O'Bannon through the Office of the State Chemist, located on the Purdue campus.

In order for a soil scientist to become registered, they must meet certain education requirements, pass a written and field examination, have field experience and have their work checked periodically by other soil scientists. The law does not limit practice to registered soil scientists but it does establish certain criteria for them to meet so they are knowledgeable on current soil science issues. The law contains a "grandfathering" provision allowing current practicing consultants to become registered until Dec. 31.

"The quality of work done to on-site septic systems is very important for public health," Franzmeier says. "This soil science registration program will enhance and protect water quality in Indiana."

For more information on becoming a certified soil scientist, contact Franzmeier, board of registration for soil scientists' chairman, at (765) 494-8065 or

Writer: Jennifer Doup, (765) 494-6682,

Sources: Don Franzmeier, (765) 494-8065,

Brad Lee, (765) 496-6884,

Don Jones, (765) 494- 1178,

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web site:
Purdue Residential Onsite Wastewater Disposal

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