300 Series S/S has been successfully used in water
containing 100 - 300 parts
per million (ppm) chlorides at moderate temperatures.
Since municipal water
is generally treated at much lower concentrations (± 4 ppm at the tap); I wouldn’t be overly concerned with filling SS tanks
with municipal water.
Notwithstanding, chronic exposure to any concentration of chlorides, especially warm stagnant water, won’t be beneficial to Stainless.
Accordingly, I’d suggest your use of the term “suspect” might be reasonably accurate.
Sorry, I`m unqualified to be more definitive.