Section 1412(b)(9) of the Safe Drinking Water Act as amended in 1996 requires that: "The Administrator (of EPA) shall, not less often than every 6 years, review and revise, as appropriate, each national primary drinking water regulation promulgated under this title. Any revision of a national primary drinking water regulation shall be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protection of the health of persons."

The primary goal of the Six-Year Review process is to identify national primary drinking water regulations for possible regulatory revision. The statute does not specifically define when a revision is “appropriate.” EPA considers a possible revision to be “appropriate” if, at a minimum, it presents a meaningful opportunity to: improve the level of public health protection, or achieve cost savings while maintaining or improving the level of public health protection.