Can local city government force individuals to purchase city water? Even if it's out of compliance with EPA standards?

I am only licensed to practice in Ohio, so my comments are limited by that restriction. In Ohio, local governments that operate public water systems ("PWS") must meet certain operating requirements enforced by Ohio EPA.  Those requirements include providing drinking water with levels of contaminants that are lower than the maximum contaminant levels ("MCLs") set by USEPA.  Currently, about 95% of PWS in Ohio are in full compliance with their permits. When the local governmental entity fails to meet the MCLs, it is required to provide the public it serves with written notice of such failure.  "Public notification is required to include a clear and understandable explanation of the nature of the violation, its potential adverse health effects, steps that the public water system is taking to correct the violation and the possibility for the need to obtain alternative water supplies during the violation." If Florida operates a similar program, I suggest that you first contact the Florida Department of Environmental Protection ("Florida DEP") to learn more about your city's contingency plans for achieving compliance with its permit, and the Florida DEP's plans for bringing an enforcement action based on those permit violations. If Florida DEP does not provide you with satisfaction, you and other similarly situated city residents may need to bring a private legal action directly against your city.  In Ohio, a citizen's right to bring a legal action against a governmental entity for damages is significantly limited by the doctrine of sovereign immunity.  In addition, a citizen is limited to bringing a "mandamus action" to force a governmental entity to undertake any particular action, even one that the law requires. That is why you need to consult a Florida attorney to determine the necessary process for bringing a legal action against your city.  I hope this helps.  Good luck.