Every person who shall own or be in possession of any premises on which there is situated on the effective date of this chapter, or at any time thereafter, a whirlpool or hot tub shall maintain on the lot or premises upon which such whirlpool or hot tub is situated a fence, wall or other adequate structure completely surrounding such whirlpool or hot tub to make the same inaccessible to small children. Such fence, wall or other structure must be not less than four and one-half feet in height with no openings except through doors or gates as hereinafter provided.