They're now mandated in Minnesota's Twin Cities region. The concept is to charge progressively higher rates for increasing volumes of residential water use. They probably are a good idea across the Great Lakes region, provided any increased revenue is plowed back into public water conservation and water quality protection, and that there is a "no-shutoff" rule for small users who simply can't afford to pay their bills. No one should have his or her water turned off. Gross users should instead subsidize "lifeline" services.