Florida is a special case, partly because the water table is so close to the surface. The result is that septic tanks are inherently unusable. Her case was about using the sewer system without paying for it. As with most places, you get a combined sewer/water bill on the theory that all the water you dump came from the city water system. This way they don't have to try to meter the sewage, too. In her case, that doesn't work and they have no other way to render a reasonable bill for her.
Had she been in, say, rural Nebraska, where a septic system was feasible, she could easily get completely "off the grid."
