Final answer:
Ultrasonic testing, pressure monitoring, and dye testing are approved methods of leak detection for an underground pressurized piping system.
Step-by-step explanation:
An approved method of leak detection for an underground pressurized piping system is ultrasonic testing. Ultrasonic testing is a non-destructive method that uses high-frequency sound waves to detect leaks or defects in materials. In this method, an ultrasonic probe is used to send sound waves through the piping system, and any changes in the sound waves (such as reflections or attenuations) can indicate the presence of a leak or defect.
Another commonly used method is pressure monitoring. This involves installing pressure gauges or sensors along the underground piping system to continuously monitor the pressure levels. If there is a sudden drop or fluctuation in pressure, it could indicate a leak in the system.
Lastly, dye testing is often used for detecting leaks in pressurized piping systems. This method involves injecting a colored dye into the system, and if there is a leak, the dye will be visible at the point of leakage.