Precast concrete septic tanks are structurally sound and watertight.
By Dean A. Frank, P.E.
There is a perception among some in the regulatory and on-site wastewater communities that the preponderance of precast concrete septic tanks leak and that it is impossible to produce a watertight, structurally sound precast concrete septic tank. However, as most of you know, this simply is not true.
You also know that a properly manufactured, installed and maintained precast concrete septic tank is the best solution for on-site wastewater treatment. Unfortunately, the misperceptions in the regulatory and on-site wastewater communities are the product of a few bad apples that have damaged the reputation of the industry. These misperceptions are further compounded because regulators have not in the past, nor do they now, consistently specify and enforce conformance to appropriate standards.
Four things are essential to the proper function of a septic tank. The tank must be watertight, it must be structurally capable of withstanding the loads it will encounter when handled and installed, it must be installed correctly and it must be maintained properly.
Septic tanks are no longer considered a temporary solution to wastewater treatment pending the installation of sanitary sewer lines. These tanks should last as long as the homes or businesses they support.
The precast concrete industry has taken steps to help ensure that tanks perform as required. In 1998, the National Precast Concrete Association (NPCA) partnered with the National Onsite Wastewater Recycling Association (NOWRA) to produce the “Septic Tank Manufacturing Best Practices Manual” and a companion video that highlights the necessary steps for producing and installing watertight, structurally sound septic tanks. This manual is highly regarded, and since publication, many regulatory agencies have modeled their regulations after it. Presumably many more regulatory agencies will follow in this direction.
What should regulators and tank specifiers do?
Require good-quality, watertight and structurally sound tanks.
Specify and enforce appropriate standards for these tanks.
Ensure that the tanks are installed correctly.
Provide end users with guidelines for operation and maintenance.
The majority of precast concrete manufacturers are quite willing and capable of producing a good quality, watertight, structurally sound, durable tank. However, regulators and specifiers have not consistently asked for such tanks. The fact is, the majority of tank producers are quality conscious, but they must compete with the minority who are not.
Verifying watertightness and structural capacity is another important step. Many manufacturers already do this with the tanks they produce. Precast concrete septic tanks are typically designed either by engineering calculations or by performance testing of the final product. Regulators and tank specifiers should ensure that this information is received from the manufacturer and that the tanks meet their requirements. Many resources and companies are available to help with both design and testing of tanks and other treatment system components.
Standards currently exist that require tanks to perform correctly and remain serviceable for the expected lifetime of the residence(s) or commercial projects the tanks support. In addition, requirements governing buoyancy and wall deflection when buried should be enforced. Such standards should be uniformly and consistently specified and enforced so that all manufacturers, regardless of the material composition of their tanks, meet the same minimum level of performance.
Installation and operation instructions are also important. If you were to buy a product from any of the big home-improvement stores, chances are it would come with installation and operating instructions. Likewise, the performance of a septic tank is heavily dependent on proper installation and operation, so you would do well to provide this information to the installer and the end user. At a minimum, installation instructions should include: handling, bedding and setting requirements, and an outline of the conditions for which the tank was designed, including the maximum depth of burial and vehicular loading. The manufacturer typically can supply this information.
Finally, the end user should be educated on the proper use and maintenance of the entire system. There are many sources for these manuals, but rarely do they reach the right hands. Most homeowners do not understand their responsibility to maintain and/or service their septic tanks.
We’re all in this together
Issues regarding septic tanks affect more than just the regulators, specifiers, manufacturers or the installers. They also affect both the health and finances of the homeowners and businesses – and even their neighbors – that rely on their proper function. As populations grow and expand into unsewered areas, this issue will continue to grow and expand with it. With more than 26 million installations in the United States, the quality, value and permanence of precast concrete septic tanks can still be relied upon to provide the best solution for on-site wastewater treatment.
For more information regarding precast concrete septic tanks, please contact NPCA at (800) 366-7731.