This Code Help episode covers UG-99 hydrostatic testing safety and common shop mistakes, stressing that hydros are dangerous and should be run with proper SOPs by experienced personnel due to past injuries and deaths. James and Jason warn against “hot bolting” (missing bolts in blinds/manways) and reusing stretched bolts and crushed gaskets, which can lead to catastrophic failures. They explain code expectations for pressure gauge hookup, emphasizing no valves between the gauge and vessel to prevent cheating and to avoid hidden pressure, and discuss zeroing gauges after tests, using two gauges, and the benefits and risks of digital gauges and chart recorders. They address calibration frequency, acceptable minor over-pressurization, stainless hydro test pressure increases due to LSR, and accident-prone moments like tightening leaks or removing blinds under pressure. They also briefly discuss combo hydro/pneumatic testing using air or nitrogen when needed.