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Gas water heaters cannot be installed in the bathroom unless they are direct-vent or they are enclosed, properly ventilated, provided with the correct elevations and clearances, and the manufacturer approves of the bathroom location.
A bathroom is a convenient place for a water heater. It would certainly be less hassle than having to venture into the attic, crawl space, or outside. And you would save time and money on having to insulate and water-proof your appliance.
I will explain the exceptions and conditions that must apply in order for the installation of gas water heaters in bathrooms to be acceptable according to code. We will also look at the reasons you might consider installing the heater in the bathroom and the instances when you should not do so.
Bathrooms Are Conditionally Prohibited Locations
Section P2406.2 of Chapter 24 Fuel Gas of the International Residential Code (IRC) says that fuel gas appliances, such as gas water heaters are prohibited from being installed in bathrooms and toilet rooms (among other locations).
However, there are exceptions and conditions controlling the details of installation and operation for the exceptions. These can also be found in Section P2406.2.
When Can a Gas Water Heater Be Installed in a Bathroom?
“The appliance is a direct-vent appliance installed in accordance with the conditions of the listing and the manufacturer’s instructions.”
A direct-vent gas water heater is a completely sealed unit. All combustion air is taken in from an outside source through one pipe and all exhausted air is eliminated directly outside through a second pipe. This means that there is no exchange of air between the water heater and the bathroom.
“The appliance is installed in a room or space that opens only into a bedroom or bathroom, and such room or space is used for no other purpose and is provided with a solid weather-striped door equipped with an approved self-closing device. Combustion air shall be taken directly from outdoors in accordance with Section G2407.6.”
This may sound a little complicated, but I will walk you through what this means.
Enclose the Heater
You should be installing your heater in a space that opens only into the bathroom. To do so, you will enclose it in space/room within the bathroom. This condition is backed up by Section M2005.2, which says:
“Water heaters located in a bedroom or bathroom shall be installed in a sealed enclosure so that combustion air will not be taken from the living space.“
By weather-stripped, the code is referring to a door with proper sealing (or weather-stripping) for ventilation purposes (discussed in a later section).
Then the regulation-required self-closing door mechanism ensures the door will close on its own and therefore cannot be left open accidentally.
Combustion Air Specifications
Gas water heaters are fuel-fired as they heat water by burning propane or natural gas. The heater requires air to burn the fuel; this is combustion air.
At this point, we have established that this combustion air cannot be taken from the bathroom, hence the weathertight and self-closing door, and it must be taken from outside.
The code further specifies how outside air must be provided. Section G2407.6, which is referenced in Section P2406.2, says this:
“Outdoor combustion air shall be provided through opening(s) to the outdoors in accordance with Section G2407.6.1 or G2407.6.2. The minimum dimension of air openings shall be not less than 3 inches (76 mm).”
These openings are designed to facilitate the inward flow of combustion air and the outward flow of exhausted air; i.e., to provide adequate ventilation, this ensures another regulation is satisfied, namely Section G2427.2 of the IRC, which states:
“Except as permitted in Sections G2425.8, G2427.2.1 and G2427.2.2, all appliances shall be connected to venting systems.”
The exceptions refer to direct-vent gas water heaters.
Why is this ventilation so important? Well, quite simply, combustion air cannot come at the cost of breathing air, and combustion by-products should never be filtered into the bathroom as this would compromise the air quality.
The IRC is quite serious when it comes to the correct installation of a gas water heater in a bathroom. Let’s go through some more regulations and rules that must be adhered to in order to make this setup safe and compliant.
Ensure There Is Adequate Combustion Air
The standard method of calculating the required combustion air for an indoor area is as follows according to the IRC, Section G2407.5.1:
“The minimum required volume shall be 50 cubic feet per 1,000 Btu/h (4.8 m3/kW) of the appliance input rating.”
In general, a ventilation rate of 50 CFM is required for each appliance, although certain appliances have higher CFM requirements. Furthermore, there are no preset combustion air rates because the supply must be specific to the appliance, so you should check the specs of your gas water heater.
An adequate supply of combustion air is extremely important to health and safety. If there is an insufficient air supply, then the combustion process will be incomplete, resulting in the production of carbon monoxide. I am sure you are aware of the hazards associated with this gas!
This is also another reason to keep the heater and its air sealed off from the bathroom; should something go wrong and carbon monoxide is released by your water heater, you do not want it seeping into your living areas.
Will the Gas Heater Be Accessible?
A water heater must have appropriate accessibility.
Section P2801.4 of the IRC states:
“Water heaters and storage tanks shall be installed in accordance with Section M1305 and shall be located and connected to provide access for observation, maintenance, servicing, and replacement.”
This means that your gas water heater must be installed in a location that will never block or prohibit any of the above actions. Not only that, but Section M1305.1 specifies that this access must not involve the need to remove any permanent fixtures.
If you cannot install the gas heat in a space that will fit all the enclosure requirements without compromising the access requirements, you should not install the heater in your bathroom.
In terms of the access requirements, if you are willing to go with this option, a tankless gas water heater may be the best fit.
Because they lack a storage tank, these heaters are much smaller and make it easier to adhere to access requirements as they don’t take up as much space.
This more bathroom-friendly option is, of course, only viable if the manufacturer permits installment in bathrooms.
Elevations and Clearances
For both elevations and clearance of the water heater, I recommend consulting your local code for any alternative regulations. You might want to call in a professional who is more familiar with the requirements.
Elevation is necessary as most fuel-fired appliances pull combustion in from the lower end, which means there must be sufficient space and opening for the air to get into the heater.
IRC Section G2408.1 says that the manufacturer’s instructions should be followed in instances where there are no specific coded regulations for the elevation of appliances. It does not mention specific elevation for a gas water heater in a bathroom.
For clearance, Section G2408.5 requires that:
“Heat-producing equipment and appliances shall be installed to maintain the required clearances to combustible construction as specified in the listing and manufacturer’s instructions.”
I would recommend using a listed manufacturer here as this makes it less complicated to ensure that the instructions from the manufacturer are all appropriate according to residential standards.
If you do that, you simply need to follow the directions for clearance that the manufacturer provides.
What Does the Manufacturer Say?
Now, I have referred to the manufacturer instructions a few times up to this point and I want to tell you why.
Because the IRC cannot provide specific instructions for every single appliance type, model, size, etc., it provides general rules and regulations and then defers to the manufacturer for the final say regarding materials used, installation protocol, and safety instructions.
Gas water heaters are no exception. Section G2448.1 of the IRC says:
“Water heaters shall be listed in accordance with ANSI Z21.10.1/CSA 4.1 or ANSI Z21.10.3/CSA 4.3 and shall be installed in accordance with the manufacturer’s instructions.”
The specific reference to listed water heaters is what ensures the manufacturer’s instructions are safe. If you have an unlisted water heater, it likely has not been subjected to the correct safety tests.
You will need to check whether or not the manufacturer has stated that their gas heater is prohibited or safe for installation in a bathroom. If the manufacturers prohibit the installation, you would be in violation of coding regulations, even if all the other conditions can be met.
This may differ across manufacturers and heater sizes. Therefore, you will need to look for a gas heater suitable for the bathroom.
Don’t Forget the Strapping
Strapping, or seismic bracing, is essential in areas that experience earthquakes.
All states adhere to basic strapping standards from the IRC (which includes specific manufacturer recommendations); however, some local codes have additional requirements.
Section P2801.8 of the IRC states that double strapping is required in areas classified in Seismic Design Categories (SDCs) D, as well as E for townhouses.
To correctly brace your water heater, it must be strapped (with two metal straps) at the upper and lower third, with the capability to withstand horizontal movement in accordance with the weight of the heater.
Reasons to Install a Gas Water Heater in a Bathroom
Some of the reasons you may want to consider installing a gas water heater in your bathroom are as follows:
- You lack the popular alternative locations such as a crawl space, garage, or accessible attic.
- You want to remove bulky appliances from your garage, giving yourself more room for parking cars, or to allow conversion the garage into a living space or bedroom.
- To save money on utility bills by putting the tank inside as the heater won’t have to work overtime to heat the water.
- So that your pipes aren’t working against the cold of a less insulated area and require less insulation themselves. There is also less pipage for the hot water to traverse.
- If your residential area is prone to power outages (for any reason), gas heaters can often be lit manually, which means you can still get hot water and you don’t even have to leave the bathroom to sort it.
When and Why It Would Not Be a Good Idea
There are some potential problems with putting a gas heater in a bathroom as this is part of the central living area.
It isn’t safe to sleep in the same room as a gas water heater. Now, I’m not suggesting that you sleep in your bathroom, but an en-suite is very nearly the same thing when the door is open.
You should not install a gas heater if there is a high risk of backdraft from the heater. This is because of the carbon monoxide released by the combustion process, which can result in carbon monoxide poisoning.
There is a higher risk of back-drafting with the following conditions:
- An oversized chimney as the ventilation system will not function correctly.
- An orphaned gas water heater as the ventilation system will not function correctly in this situation either.
- An airtight house as this will impact the availability of combustion air.
My Recommendation: Seek Professional Advice
When it comes to gas appliances in living spaces, there are rigid and specific rules and regulations.
The installation process also involves several factors such as sealing spaces, venting, and combustion air calculations for which knowledge and experience are invaluable.
While I like to install things myself, in this case, I would recommend you consult a professional. Someone who is well-versed and familiar with local codes for your area and can help you set up everything according to the specifics of your bathroom.
Related article: Can a Gas Dryer Be Installed in a Bathroom
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