What is one of the WAC requirements for testing the water-tightness of a holding tank after installation?

Filling the holding tank with water at the site is a critical requirement for testing its water-tightness after installation. This process ensures that the tank can withstand operational conditions and check for any leaks that could compromise the system's integrity. When the tank is filled with water, it simulates the conditions the tank will experience during normal operation, allowing for accurate detection of any potential problems.

Water testing is a standard method in ensuring that the seams, joints, and overall construction of the tank are sealed properly and can handle the pressures and environmental factors they will face in use. This procedure is essential for maintaining environmental safety and preventing contamination of groundwater.

Other options, such as testing after the first pump-out or filling the tank with sand, do not align with best practices for leak detection. Additionally, testing a tank that is buried underground would not provide the opportunity to visually inspect and assess its integrity for leaks effectively. Therefore, filling the tank with water directly at the installation site is the most reliable method for ensuring it is water-tight and ready for use.