Does a gas water heater, manufactured in 2024, have to be raised 18 inches off of the floor of the garage, if the water heater is in an enclosed, utility room, at the end of the garage?
That is up to your local AHJ.
Since you didn’t bother telling us your location, or anything else for that matter, any reply is purely a WAG!!
I think JJ is correct in saying it’s up to the local AHJ to dictate installation. The 18" rule was set for the WH’s open combustable flames being safer with other vapors from the garage that might ignite. Closed systems seem to have eliminated that issue to a point. But keep in mind, some AHJs require bollards placed in a garage to protect a water heater from impact. In a utility closet, I don’t know for sure/
FVIR doesn’t automatically override the local AHJ requirements.
We see inspectors questioning their local AHJ’s mandates all the time on MB discussions.
Guess what… they (AHJ’s) have the right to adjust requirements for their specific jurisdictions.
As I mentioned…