What should tightness tests account for during testing?

Tightness tests for underground storage tanks (USTs) are critical to ensure that the tanks are not leaking and are functioning safely and effectively. The correct choice emphasizes the importance of accounting for thermal expansion and various environmental factors during these tests.

When conducting a tightness test, it is essential to consider thermal expansion because the temperature of the stored liquid can vary, affecting the liquid's volume and pressure inside the tank. This can lead to false readings if the test does not account for changes in liquid expansion. Additionally, environmental factors such as temperature fluctuations, soil conditions, and external pressure can impact the integrity of the tank and its fittings, making it crucial to include these factors in the testing process to ensure accurate results.

By incorporating thermal expansion and environmental considerations, the tightness test can provide a reliable assessment of the tank's integrity, ensuring that any potential leaks are detected and addressed promptly.