4.7.2 Pressurized Piping Systems
All piping that operates under pressure and that is part of a UST system must be equipped with an automatic line leak detector (ALLD). An ALLD can be either mechanical (MLLD) or electronic (ELLD) in function.
Single-wall piping systems must also have a precision tightness test conducted on an annual basis. This test must be capable of detecting a leak rate no greater than 0.1 GPH at 10 psi operating pressure. As an alternative, single-wall piping can be monitored on a monthly basis using a leak detection method capable of detecting a 0.2 GPH leak rate.
Various methods of leak detection can be used for pressurized piping. The two methods discussed in this course are:
1. Interstitial Monitoring
2. Pressurized Line Leak Detection