Google "Bollard"

Just because something is a current standard doesn't typically mean that an existing house needs to be brought into compliance. What prompted this inspection? Are you selling the house, or did you just buy it or what?

A bollard is typically a several foot long steel pipe that is several inches in diameter, and is either put in the ground with concrete poured around it, or it has a flange plate that is welded to the bottom so you can bolt it to the concrete floor. Doing it yourself would probably be fairly easy if you have some basic skills, and the bollards could be bought from a supply house for about $100 apiece.

IRC 1307.3.1 & UPC 510.3 state that a barrier or elevation is required to protect a water heater from damage when installed in a garage or carport.

Typically a bollard is a piece of 3" or 4" steel pipe that is set into the concrete and extends upwards to a specified elevation. The pipe is then concreted into the floor and the pipe is filled to the top with concrete. Although not required, it is customary to extend the concrete fill slightly above the top of the pipe and it is rounded to provide a finished appearance.

Notice that I did not give specific depths or heights of the bollards. While the code requires bollards the actual dimension of the bollards is determined locally, by example, in my jurisdiction we are required to use 4" diameter steel pipe which is set a minimum of 24" below finished grade and they must extend upwards to 40" above finished grade. We may also use 4" I-beam provided it meets the burial depth and height requirements.

In my community the bollards must be painted red or yellow for visibility.

In another community near here they will permit 4" PVC pipe providing you install 4 pieces of #5 rebar in the pipe, then concrete fill.

To save money you may buy the pipe at a scrape yard