Arizona Plumbing Practice Exam

All of the following materials are approved for the construction of septic tanks EXCEPT:

1. Pressure treated redwood

2. Fiberglass

3. Concrete

4. Polyethylene

The correct answer is: Pressure treated redwood

When it comes to construction materials for septic tanks, certain standards and regulations dictate what is acceptable for ensuring durability, safety, and effectiveness in sewage treatment. Among the listed materials, pressure treated redwood is not typically approved for septic tank construction due to concerns over its longevity and the leaching of chemicals used in the pressure treatment process. While wood can be durable in certain applications, it is susceptible to rot, decomposition, and damage from the anaerobic conditions typically found in septic systems. In contrast, fiberglass, concrete, and polyethylene are recognized for their structural integrity and resistance to the corrosive and aggressive nature of wastewater. Fiberglass is lightweight and durable, easily molded to different shapes without compromising strength. Concrete is widely used for its robustness and ability to withstand substantial pressure, especially in underground applications. Polyethylene is another popular choice because it is resistant to corrosion, easy to install, and generally has a long service life. Each of these materials has been tested and proven to be effective for use in septic systems, unlike pressure treated redwood, which lacks the necessary properties to ensure the proper functioning and longevity of the septic tank.