A New Benchmark for Quality Assurance in Septic Tanks
By Phillip Cutler, P.E.
The recent release of an ASTM testing standard creates a new benchmark for quality assurance that could boost the marketability of precast concrete septic tanks.
ASTM International’s new ASTM C1719, “Standard Test Method for Installed Precast Concrete Tanks and Accessories by the Negative Air Pressure (Vacuum) Test Prior to Backfill,” was developed under ASTM’s technical sub-committee C27.30, which falls under the main ASTM Committee for precast products, C27.
Prior to the release of the new standard, precast manufacturers, engineers, specifiers and regulators could rely only on a manufacturing reference for testing watertightness of precast concrete septic tanks – ASTM C1227, “Standard Specification for Precast Concrete Septic Tanks.” The new C1719 standard contains elements of C1227 for septic tanks and is also similar to the previously developed ASTM C1244, “Standard Test Method for Concrete Sewer Manholes by the Negative Air Pressure (Vacuum) Test Prior to Backfill.” ASTM C1719 is different from C1244 in that it provides a vacuum test method for installed precast tanks and accessories as an “installed system.” The scope of the new C1719 standard covers tanks for onsite wastewater treatment and storage, grease interceptors, grit/oil separators, water storage and other applications requiring watertight construction and installation.
Excellent marketing tool
The new C1719 standard can be used with confidence by manufacturers and installers of precast tanks and systems as a marketing tool for their businesses when asked by an Authority Having Jurisdiction (AHJ) for an ASTM test method of the effectiveness of an installed system. Armed with this nationally recognized and consistent negative air pressure (vacuum) method for testing watertightness of systems prior to backfill also eliminates the need of carting huge quantities of water to your site for a water test. A water test, while serving the purpose for testing a tank, does not completely address the entire installed system (as does the C1719 vacuum test) and is clearly much less sustainable. What do you do with all that water after the test is complete?
Test equipment and method
The equipment required to perform a negative air pressure (vacuum) test is not sophisticated. As stated in section 6 of the C1719 standard, the testing equipment consists of pumps, vehicle vacuum devices and even a high-performance shop-style vacuum cleaner. Most devices are easily operated and the test can be performed in a few minutes using the vacuum method, unlike the hours or even days needed to perform the same test with water.
Like ASTM C1227, C1719 tests apply a vacuum to the sealed system to a level of 4 in. of mercury (Hg) for a duration of five minutes. If the gauge holds without pressure loss, the system passes. If the vacuum level drops, it is reapplied and the test is restarted. A tank or system failing to hold vacuum may be repaired per the manufacturer’s recommendations and/or evaluated for not holding negative pressure and retested following such repair.
Manufacturers and installers of precast tanks should notify and promote to their local AHJ that these standards exist and are the best tools to adopt for the production of precast concrete septic tanks and for watertightness testing of tanks of all types and installations. Those regulating and specifying communities requiring watertightness testing of tanks and systems after installation and prior to backfill can be assured of a precast concrete system’s watertight integrity by using the C1719 standard.
Phillip Cutler, P.E. is the director of Technical Services and Plant Certification for NPCA.