First thing you want to research is the city ord it self that they claim is requiring your connecting to the public system, you want to research your city county ords that address property in areas where private well and septic are still in use what your looking for is a ord that spells out under what conditions a property must connect when public systems are available , example county/ city wrote ord saying that when a onsite septic system fails and public connections are available then a home must connect. Failure = tank cave in, drain field failure, tanks rusted out etc. when I was growing up our burb had put in city water /sewer we were allowed to stay on private well & septic but then our sand point began to fail. no choice my folks had to connect to city water and sewer. If there are any exclusions you want to argue that you do not have to hook up, BUT beware some public util do offer discounted tap fees first time around , Now as to forcing you to pay for it, If your able to escape connection for now, since it is public water and sewer they will have a means to determine what some one must pay its called a meter , In some places I know of people have public sewer but keep private well , they pay a qaurterly rate for sewage based on number of bedrooms & bathrooms. NOW one other thing they can do is assess you cost related to public water and sewer in that road and some places even create tap points for future connection and the fees for them could be added in to the general assessment. LAST know this if you escape connection and are planing on selling in the next few years it is a selling point to be on public system since your city /county could also create a ord later on forcing the connection of homes at the time of transfer too. All this is due to the many years and years of people using non conforming systems, old systems in poor shape, screwing up ground water around them especially when they were on small lots like my dads home which was built during a time when there was no set standards, in the 50s and 60s there were entire subdivisions that after a few years where homes were screwing up each others water. You might find in the end there is nothing else you can do but connect , but you can learn if your able to retain the well for garden / car washing use , if you are then at least research what the eventual cost of capping it will be and having your septic tank either filled in or crushed so that way some day neither you nor grandkids or anyone else can be injured by it when it caves in. BTW should you find you just dont understand the language in the ords use the links above and at least arrange for someone to help you go over them , it may well be worth it if its a hard read and you end up missing something.