A water tank treatment system includes a water tank having an inner cavity for storing water therein, the water tank having a threaded opening; and a treatment device with a body forming an inner area, the body is configured to threadingly attach to the threaded opening; an absorbent material disposed within the inner area, the absorbent material is configured to absorb and treat acidic gas passing through the threaded opening; and a color changing indicator extending through a thickness of the body and in communication with the absorbent material.