A question about water heaters

[Anthony A. Cassady]

Do water heaters always have to be elevated and if so what is the reasoning?

[Mark Nahrgang]

No. They only have to be elevated in garages. And even then only some of them have to be. In a garage, gas fumes accumulate at the floor. The ignition source of the water heater, can (and has) ignite those fumes and burn down the house. Elevating the water heater 18 inches, places it above those fumes, thus reducing the probability of an explosion.

[Anthony A. Cassady]

I knew about garages but didn't know if one would have to be elevated in a basement or not. Alway better to double check I guess.....thanks

[Paul Pendley]

Keep in mind that you are in MO. Some of those homes are Garage/Basements if I remember right. Im talking about the homes built into a hill side where the basement/garage is usually on the backside of the home. Please correct me if im wrong which im sure some people will.

[Chuck Evans]

In garages and rooms that open directly into garages, all sources of ignition (includes thermostat, elements etc for electric water heaters) must be 18 inches above the floor.

[Michael R. Boyett]

and rooms that open directly into garages

You know Chuck, I have thought the same thing and have been writing them up as such for the last couple of years. The 2006 IRC Commentary doesn't seem to support that though or, at least, it is 'qualified'...see the last sentence of the 1st paragraph:

To reduce the hazard of fire or explosion from possible
gasoline leaks from automobiles, appliances having an
ignition source must be elevated to keep the ignition
source a safe distance above garage floors. Commentary
Figure M1307.3 shows a water heater installation
that complies with these requirements. In the context of
this section, a source of ignition could be a pilot flame,
burner, burner igniter or electrical component capable
of producing a spark. The term “ignition source” is defined
and can be interpreted as meaning an intentional
source of ignition for any flammable vapors that may be
present. See the definition of “ignition source.”
An appliance installed in a closet or room that is accessible
only from the garage must be considered as
part of the garage for application of this section. Even
though the room may be separated from the garage by
walls and a door, there are no practical means of making
the door vapor tight nor is there any assurance the
door will remain closed during normal use. An appliance
room that is accessed only from the outdoors of
from the living space would not be considered as part
of the garage. Rooms such as utility rooms or laundry
rooms that communicate with both the garage and the
living space are considered as part of the living space
and not part of the garage.

Even though appliances in the garage must be protected
from impact by automobiles by the installation
of substantial barriers, elevation of the appliance may
not be sufficient to guard against damage from impact
unless the building official determines that the platform
is of substantial construction material capable of withstanding
impact.

Note that many newer gas-fired water heaters now
have flammable-vapor-resistant systems that allow
them to be installed on the floor without the 18 inch
(457 mm) elevation (see commentary for Section
G2408.2). However, appliances in this chapter are not
gas-fired and, therefore, must be elevated in accordance
with this section.

[Anthony A. Cassady]

Thanks guys....the home does have a garage but it is above grade and the basement is just a basement...no issues.