Daniel, I'm sure no expert on this either but I have seen a lot of variation on the requirements for water heater installations, depending on the area of the country. In places where earthquakes and/or slab built homes are common, a safe escape route for the hot water is also an issue--if freezing is also not an issue. I was kind of expecting BobF to check in on this one but others in that type of locale might also be able to comment.
Really, I do suggest that Jean's best bet is to check with her local building authorities.