About 5 years ago I replaced a gas water heater and used 18" flex SS braide d pigtails between the unit and the pipes. Last night a flex coupler devel oped a spray, flooded the garage, and ruined the wall panel.
Come to find out the flex connectors are plastic pipe with a SS braid cover ing. The flex ends at the wall pipes were good & solid but the ends at the water heater were totally mush/putty like! It looks like the heat from th e tank or the heat from the flue had dissolved them over time. Will never use them again! I used solid corrigated SS flex this time and won't have t he plastic to worry about.