Although the problem of chloride stress corrosion cracking (SCC) of austenitic stainless steel drain lines in hydroprocessing units has been well known for many years, new questions on these deadlegs are arising with the renewable units handling biofuel feeds. Some potential issues are in the hydrodeoxygenation (HDO) units and certain pretreatment units, wherever these units have high pressure SS piping. Many of the hydroprocessing unit case histories of leaks and cracks occurred shortly after startups from turnarounds and were attributed to water not being drained before startup. In contrast, some of the renewable units may have a risk of water condensing in deadlegs even during normal operation. The hydroprocessing unit case histories have been compiled to help to define the conditions, such as main line operating temperature and pressure which contribute to SCC in the deadlegs. The process chemistry, especially water content, oxygen and pH differences between the refining and renewable units are reviewed, and material recommendations are given for drain lines and other deadlegs in each type of unit.