Dave diy, yes to add confusion different codes apply to different areas mostly by state . as far as I know all CA has ca plumbing code based on the UPC. Hope this makes sense.
might be of interest that a guy on here lived in some back east state in an apartment building and was mad that inspector didn't require protection . water heater had no pan and t and p was dumping on floor like in a hall closet or perhaps kitchen area not clear but within the apt unit. it was evidently "grandfathered in " legal.
You seem to be getting it under control Dave, didn't know but back in 79 that was pretty common . and in fairness its difficult /expensive to get compliance at times , shortcuts get taken by many. if you can get the drain into garage with a 1 inch PVC and turn maybe run 5 feet or so I wouldn't think too much cold air would come into laundry area, kinda late now but having the tank up off floor say 3 inches would have let your drain pipe go through wall missing the sill plate