IAPMO R&T certifies septic tanks to the requirements of the ANSI/IAPMO Z1000 standard, as well as the requirements of the UPC and the International Plumbing Code (IPC). The standard covers septic tanks made of several different materials. Our product evaluation engineers enjoy reviewing calculations for septic tank product certification because they use many of the engineering fundamentals for such reviews.
 
The majority of the septic tanks certified by IAPMO R&T are made of precast concrete with steel reinforcements. The calculations submitted for such products are based upon the requirements of the standard, which include earth load as well as highway loads based on the location of installation. Many clients submit design calculations. Such calculations get deep into civil engineering, although mechanical engineers with design and structure background can handle such reviews, as well. In design calculations, the strength of the materials is known. The engineers calculate the thickness of the concrete and the center-to-center distance of the rebars for a selected rebar number.
 
We also certify plastic septic tanks. The calculations for such tanks are more closely related to the mechanical engineering field. Such tanks may be considered as thin wall vessels. Such plastic tanks can be considered as cylindrical vessels. In such tanks, the radial stresses are negligible in comparison with the tangential stresses because the material thickness is negligible in comparison with the diameter of the tank. In such cases, the stress is dependent on the average diameter of the tank, the resultant pressure and the thickness. In these instances, the tank thickness can be determined for production purposes.
 
In recent years, some manufacturers use finite element analysis (FEA) for such submittals. This analysis, because it is three dimensional, is much more accurate and much more representative of the real world.
 
Septic tanks inspections are very thorough. During these inspections, the tanks undergo a variety of measurements, such as the location of the rebars, the manhole dimension and the location of the baffles. Concrete septic tanks as mention before include steel reinforcements. This gives the tank tensile strength. But the compressive strength comes from the concrete. Therefore, in order to assure that the material strength of 4,000 psi (compressive) is met, concrete cylinders are crushed in universal testing machines to assure compliance. Among other inspection requirements is a water test.
 
For further information regarding certifying septic tanks, please contact us.