The other thing that is worth investigation is that Stainless and hot salt water are not too good for each other.. It may be that the stainless here doesn't get hot enough to cause any heavy corrosion..
Yeah, I'm trying not of think of chloride stress corrosion and trans-granular cracking. Maybe no internal stresses and maybe not hot enough to cause problems. I've got to admit mine is cool to the touch at full load.
Some years ago, I remember looking at a buried 304 SS condensate return line which was operating at a continuous 212 deg. F. The back fill which the contractor used on the bare SS tubing was Fraser River sand and was subject to tidal backflow from the Pacific Ocean. Analysis showed a pretty high chloride content. Where the tensile stress was greatest in the line, the tubing was loaded with large cracks, otherwise, looked pretty good. Not a good project from start to finish.
Every so often, SS can be funny stuff and fail when and where you least expect it. For this reason, when I install the 316 SS elbow, I'll be pulling it every year to stick my nose in to see if anything untoward is happening.