It’s Not Your Father’s Septic Tank Anymore! (Part 3 of 3)

Precasters Failing to Recognize the Importance of the Shift in Attitude Toward Septic Tanks Are Likely to Find Themselves on the Endangered Species List

In addition to funding onsite treatment research projects, the U.S. EPA published onsite guidelines. One such publication was the 1980 Design Manual: Onsite Wastewater Treatment and Disposal Systems. The 1980 Manual described onsite treatment systems by detailing the individual system components such as septic tanks, sand filters, alternative treatment units (i.e., aeration systems, etc.). The emphasis of the manual was to list the prescriptive requirements of each of the components. Prescriptive requirements refer to how the components were to be made, what they were to be made from, and how to select the proper size or number of components for a system.

1980 Design Manual: Onsite Wastewater Treatment and Disposal Systems

Section 6 of the Design Manual included the following description of a septic tank. “Septic tanks are buried, watertight receptacles designed and constructed to receive wastewater from a home, to separate solids from the liquid, to provide limited digestion of organic matter, to store solids, and to allow the clarified liquid to discharge for further treatment and disposal”. The Design Manual went on to describe tanks as either having a single or two compartments, with baffles and gas deflectors to prevent solids from escaping into the drainfield. Access risers normally came to within six inches of the ground surface to allow easy access for cleaning but by remaining buried unauthorized access was prevented.

Septic tanks described in the 1980 Design Manual resembled the type of tanks that “your father traditionally made.” The authors also included the following commentary when describing concrete, polyethylene, and fiberglass tanks: “The most commonly used construction material for septic tanks is concrete. Virtually all individual-home septic tanks are precast for easy installation in the field … Plastic and fiberglass tanks are very light, easily transported, and resistant to corrosion and decay. While these tanks have not had a good history, WHILE THESE TANKS HAVE NOT HAD A GOOD HISTORY, some manufacturers are now producing an excellent tank with increased strength.” (Excerpt from Section, emphasis added.) Interestingly, the authors admitted that polyethylene and fiberglass tanks did not have a good reputation.

When discussing ongoing operation and maintenance of a septic tank, the manual focused on inspecting tanks no more than every two years to determine sludge accumulation rates. The manual further recommended that in the absence of an ongoing inspection program, tanks should be pumped at least every three to five years. There was no mention of tank manufacturers supplying a “How to Maintain Your Septic Tank” homeowners’ guide. There was no recommendation to use effluent filters to replace gas deflectors to better protect against solids flowing from septic tanks and ending up clogging drain fields. Supplying a tank meant that the tank be structurally sound, the proper size, and properly installed.

Sometimes you can learn as much from what information is not included as from the items discussed. In the 1980 Manual, there was no discussion of field studies citing multiple failures of precast concrete tanks due to structural collapse. There were no references to improper installation techniques which resulted in a phenomenon commonly referred to “differential settlement”. [Differential settlement is the alleged condition of multiple pieced concrete septic tanks coming at the joints caused by post-installation settling.] Interestingly, the only negative comments regarding tank materials were the before-listed comments “these tanks (referring to polyethylene and fiberglass) have not had a good history.”.

2002 Onsite Treatment Systems Manual

In 2002, the U.S. EPA published a new manual, Onsite Treatment Systems Manual. The new manual shifted the focus from the prescriptive aspects of the 1980 manual to the new perspective of building onsite treatment systems focusing mainly on performance. A performance-based management program makes use of recent developments to select and size system technologies appropriate for the estimated flow and strength of the wastewater anticipated to be generated. Considerations such as soil texture and expected daily flow rates, effluent strength become the focus for designing the system. Terms such as infiltration surface, minimum separation distances, and hydraulically restrictive layer become commonplace when discussing soil characteristics. Operation and maintenance (O & M) programs become important components of a system.

Septic tanks under the performance-based focus are described as, “The tank provides primary treatment by creating quiescent conditions inside a covered, watertight vessel which is buried. In addition to primary treatment, the septic tank stores and partially digests settled and floating organic solids in sludge and scum layers … and the tank conditions the wastewater by hydrolyzing organic molecules for subsequent treatment in the soil or by other processes.” (Excerpt from Chapter 4, page 4-37.) How many precasters take into consideration how well their tanks will “hydrolyze organic molecules” when they design a tank?

The 2002 Manual further comments on the materials used for septic tanks, stating, “Precast concrete tanks are by far the most common, but fiberglass and plastic tanks are gaining in popularity. The lighter-weight fiberglass and plastic tanks can be shipped longer distances and can be set in place without a crane. Concrete tanks are less susceptible to collapse and floatation.” (Excerpt from Chapter 4, page 4-42.) Notice the subtle shift away from concrete being the favored material for tanks. Septic tanks become much more than an underground sewage storage structure under the new performance-based approach to onsite sewage treatment.

Just as the 1980 Manual was informative for the items it failed to include the 2002 Manual is equally informative. The 2002 Manual fails to include information regarding catastrophic system failures due to structurally deficient precast concrete tanks, nor does the report include references to the condition known as “differential settlement.” One cannot help but wonder why two EPA reports, separated by 22 years of experience, failed to warn the industry against conditions that have been promoted in recent years as being the ruination of the onsite industry. Both the 1980 and 2002 publications are available on CD, titled Onsite and Clustered (Decentralized) Wastewater Treatment System: Informational Materials at

In Conclusion

Darwin pointed out that “each new species is produced and maintained by having some advantage over those with which it comes into competition.” Proponents of alternative materials such as plastic and fiberglass septic tanks would like nothing better than to have new onsite regulations place them in a position of superior competitive advantage. Precasters need to realize that if this happens then the second half of Darwin’s theory will occur “and the consequent extinction of the less-favored forms almost inevitably follows”. Technological advances in manufacturing processes, such as the use of self-consolidating concrete, give precast manufacturers new advantages to compete against the challenges of alternative materials. Advancements in tank sealants, resilient connectors, tank filters, and access riser assemblies give precasters new advantages to compete against the challenges of alternative materials. Precasters should never overlook the advantage they have when the topic is the inherent strength concrete has as a building material. Knowledgeable industry personnel know better than to fall for the erroneous argument that plastic or fiberglass tanks have superior load-bearing capabilities than a well-made concrete septic tank.

Figure 1. Cartoon originally published, Earth Day 1971, by Walt Kelly

Is it possible that precast concrete septic tanks will become extinct in the onsite industry? Unfortunately, the answer to this question is possibly yes. Too often precasters focus on fellow precasters as being their main competition. This is evidenced in geographic areas where the price of septic tanks barely covers the material costs of manufacturing the tank let alone accounting for overhead expenses. Forget about any profit. Additional evidence of a precaster having his focus on the wrong competitor is his voicing a reluctance to participate in new onsite associations whether at the local, state, or national level, and a reluctance to become involved in industry quality assurance programs. Or, worst of all, a willingness to concede defeat by simply getting out of the business due to the frustrations of having to adapt to the changing onsite environment. Precasters need to overcome the immortal words of that legendary sage from the Okefenokee Swamp, Pogo, “We have met the enemy and he is us.”

This blog series, The Evolution of Onsite Sewage Treatment, is part 1 of “It’s Not Your Father’s Septic Tank Anymore”. The series is intended to provide information on the current state of the onsite wastewater industry and the future role of precast concrete septic tanks. Part 2, titled What Do We Mean We Need to Test Everything? focuses on quality assurance programs and testing requirements with a special twist. Part 3, titled Good News, There’s a Heck of An Opportunity Here, focuses on the potential business opportunities which are the result of new regulations.

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