Arizona Plumbing Practice Exam

The sidewalls of a septic tank must extend how many inches above the liquid depth?

1. 6 inches

2. 9 inches

3. 12 inches

4. 15 inches

The correct answer is: 9 inches

The requirement for septic tank sidewalls to extend above the liquid depth by a specific measurement is rooted in the need for effective wastewater management and structural integrity. The correct measurement of 9 inches ensures that there is adequate space to account for fluctuations in the level of the liquids within the tank due to factors such as rainfall, inflow from household use, or effluent flow. This height helps minimize the chances of overflow or backflow situations that could lead to environmental contamination or malfunctions in the system. While other options might seem viable, they either provide too little or too much clearance. A measurement below 9 inches could increase the risk of overflow, impacting both the efficiency of the septic system and the surrounding environment. Conversely, a greater height than necessary could lead to additional structural concerns, including the potential for increased pressures on the tank materials and the surrounding soil. Thus, the correct extension of 9 inches above the liquid depth is crucial for ensuring the proper functioning and longevity of the septic system while protecting environmental health.