There are other issues to consider as well – due to changing tank footprints and sizes – sometimes it’s more cost effective for a home owner to install a new tank on a stand and sometimes it’s more cost effective to remove a stand and install a water heater on the garage floor. (The situation differs home by home and is determined by how much repiping needs to be done, if the stand is in good condition and can be reused and whether or not there is vent/flue work required to make sure the vent is installed and sized properly.)
And, installing a FVIR (post 2003) water heater on a floor is safe. But, because of how dangerous it was prior to 2003, homeowners, retailers, and inspector sometimes apply the old safety requirements on current technology where it is no longer relevant. This can be confusing as a home owner can get conflicting information about proper installation.
In most cases, we will install an FVIR water heater on a stand in a garage -because a) it’s more cost effective and b) requires less explanation if someone is applying outdated standards. But, if there is a good reason – for example installation cost, water heater sizing issues and maintaining positive vent slope being the most prevalent reasons to not elevate the tank – it is a safe and reasonable solution to put an FVIR water heater on the garage floor.