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.