Not too many areas require permits for changing out fixtures. Even those that do, don't normally hassle you over the existing installations unless it is just totally unsafe. In Ohio, when you bought a water heater, the stores were required to submit the sale to the Code Department. There were also inspectors looking for old heaters sitting at the curb for the garbage men. One reason for this was Handymen who did no other work than Water Heater installation, and had no contractors license and paid no taxes.
If you have never made a mistake, you haven't done much.