There is a lot of misinformation on the internet about this topic. This is likely because most of the articles are outdated and people just repeat what they heard from someone else. Let’s clear it up once and for all whether a water heater can be placed directly on the floor or not.
Gas water heaters can sit directly on the floor if they are FVIR(flammable vapor ignition-resistant). All gas 30, 40, and 50-gallon water heaters sold to the North American market after 2005 must comply with ANSI Z21.10.1a-2002 standards and are FVIR.
All electric water heaters can be placed directly on the floor.
The reason why people still think it is necessary to elevate the water heaters is that gas water heaters without FVIR were a serious fire hazard when placed directly on the floor. In-fact it was required to elevate them 18 inches from the ground.
This is no longer relevant for FVIR certified gas water heaters, but some homeowners and home inspectors still request the water heater to be off the ground. Even though there is no practical need for it.
Why Were Water Heaters Elevated In The Past?
Gas water heaters without FVIR were required to be 18 inches off the ground. Measured from the pilot light to the ground. This was to prevent accidental ignition of spilled combustible liquids such as gasoline, thinner, paint, etc.
Again, there is a lot of misinformation about this on the internet. Some say that the gas itself will explode some say it will rust and then explode, but in reality, it was spilled flammable liquids that were ignited by the pilot light.
Many homeowners place their water heater in a garage. It is very likely that gasoline or paint thinner or something else flammable is stored in a garage.
An open chamber water heater(non-FVIR) that sits directly on the floor will easily ignite any spilled gasoline vapors and this is the reason why it is so dangerous.
That’s why it was required to elevate the gas water heater at least 18 inches from the ignition point.
If you are unsure if your gas water heater is FVIR by all means install it 18 inches off the ground.
Are All Gas Water Heaters FVIR?
All 30, 40, and 50-gallon gas water heaters sold in North America after 2005 are FVIR(flammable vapor ignition-resistant). They must comply with ANSI Z21.10.1a-2002 standards, according to that, the fumes from spilled liquids can’t be ignited by the pilot light.
Smaller than 30 gallon gas water heaters are not required to be FVIR, I have not found out the reasoning behind this. They still need to be elevated at least 18-inches measured from the pilot light.
The same goes for tankless/instant gas water heaters.
The easiest and most reliable way to check if your water heater is FVIR is to check the owner’s manual. Google product code + manual.
Some manufacturers require their water heaters to be elevated even if they are FVIR. This can be to achieve the certified energy rating, or for inspection purposes.
If you visually see the pilot light or are able to light the pilot with a match, then you do not have an FVIR water heater and it must be elevated at least 18 inches.
Do FVIR Water Heaters Need to Be Elevated
A gas water heater that is FVIR(flammable vapor ignition-resistant) does not need to be elevated, since there is no risk of igniting spilled liquids.
Always consult your product manual and building codes before installation, as there can be model-specific reasons why it must be elevated.
Is There Any Other Reason To Elevate A Water Heater?
Even though it is not required to elevate a FVIR gas water heater, there are some advantages to doing so, especially in a basement.
As we have already covered, new water heaters do not pose a fire risk when placed directly on the floor, but there are still a couple of reasons why it might be a good idea to lift it off the ground Using a water heater stand (Amazon link)
It is impossible to inspect the bottom of the water heater if it is sitting directly on the floor. This might seem irrelevant now, when the water heater is new.
However, it is beneficial to have visual access to the bottom for yearly inspection. This can help spot any problems before they get out of hand.
A water heater stand makes inspection very easy and in the same time protects your expensive investment from flooding and rust.
Water heaters are often placed in basements or garages. In case of a flood having the water heater off the ground gives you time to pump out the floodwater before any damage occurs.
When placing a water heater in a crawl space it is vital that it is lifted off the dirt or gravel.
It is easier to drain the water heater if it is higher off the ground, especially if the drain valve is plugged and must be cleaned before the water heater can be drained. Sometimes it is difficult to empty the water heater completely when it is directly on the floor.
It is the last of the water that contains the most contaminates, that you want to remove.
The logic is that the cold concrete slab will absorb some of the heat from the water heater. Therefore you would spend some of the energy on heating the slab.
While this might have been a problem in the past, when the water heaters were very poorly insulated; modern water heaters are insulated so well to comply with energy efficiency regulations that they lose very little heat.
There can be some marginal energy savings by lifting the water heater off a concrete floor. But in my opinion, the savings are so small, that it’s not worth the effort.
It’s not worth doing it just for the energy savings. However, if your basement/garage floor is often damp and there is a risk of flooding and you will buy a water heater stand anyway; the small energy savings will be a bonus.
Can Electric Water Heater Sit on Concrete Floor?
Electric water heaters can sit directly on the concrete floor. There is no risk of accidental ignition of spilled flammable liquids with electric water heaters. They do not have pilot lights as do the gas counterparts.
Electric water heaters never have been required by building codes to be on a stand or lifted up. The only reason why you would want to have them off the ground is to save energy or protect the water heater from flooding/rust damage.
Can You Put Water Heater on Bricks?
One layer of bricks can be used to lift the water heater off the ground. This can help protect the water heater from moisture if the floor that it is sitting on is known to be wet from time to time.
It is important to not stack the bricks on top of each other. Multiple layers of loose bricks will not make a sturdy base for the water heater. When someone or something hits the water heater, it could tip over and cause a lot of damage.
This is especially important in regions where earthquakes are common.
As you know anon-FVIR(flammable vapor ignition resistant) gas water heater must be elevated 18 inches measured form the pilot light. NEVER should this be attempted with bricks. The 18 inch loose brick column will be so unstable that the slightest movement will tip over the water heater.
Instead invest in a quality water heater stand instead.
The vast majority of the gas water heaters sold today are FVIR(flammable vapor ignition resistant) and are not required to be elevated. There are exceptions to this so be sure to check your owner’s manual before installation.
Electric water heaters can always be placed directly on the floor.
There are some valid reasons why one might want to still use a water heater stand, even though not required by code. They are energy savings, flood protection, and minimizing rust.
Hope you got a clear overview of the topic.