What must be done to the piping before backfilling?

Before backfilling, it is essential to conduct isolation and tightness testing on the piping. This process ensures that the piping system does not have any leaks and is functioning as intended. Isolation testing involves separating the system from other components to determine if it retains pressure, confirming that there are no undetected leaks or weaknesses in the system. Tightness testing checks for any potential leaks by subjecting the piping to pressure, thus verifying its integrity.

Completing these tests prior to backfilling is crucial because once the soil or other backfill materials are added, access to the piping for subsequent testing becomes significantly more difficult, if not impossible. Ensuring that the piping is sealed and operational before it is covered protects against future risks, such as environmental contamination due to leaks or contamination of the surrounding soil and groundwater.

The other options, while important in their respective contexts, do not specifically precede backfilling as directly related to ensuring the immediate integrity of the piping system.