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Can a Tankless Water Heater Be Installed in a Crawl Space

Crawl spaces seem like an ideal spot for water heaters. They are out of the way but still close to the house and water and power supply points. The issue for me was always the idea of having to get a big water tank into the space, but now tankless water heaters are available, which seems to be the solution to this issue.

A crawl space can be an excellent place to install your tankless water heater but there are some environmental, installation, and code regulations to consider. Let’s look at some of the code requirements and other factors you should consider if you want to install a tankless water heater in your crawl space.

The IRC does not prohibit installing tankless water heaters in the crawl space. However, the manufacturer and code installation conditions must be adhered to, including accessibility, lighting, ground clearance, pipe protection (freezing), and flood protection. The casing and components should be durable.

Is It Against the Building Codes?

According to the IRC Section M2005.2.1:

“Access to water heaters that are located in an attic or underfloor crawl space is permitted to be through a closeted location in a sleeping room or bathroom where ventilation of those spaces is in accordance with this code.”

So, while the IRC does not expressly say that tankless water heaters can be installed in crawl spaces, the above-quoted regulation implies that it is not prohibited to install a heater in a crawl space.

However, there 2 are conditions to this allowance according to Section M2005.1:

  1. The installation must be up to code.
  2. The manufacturer’s instructions must permit it.
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Thus, if you do your research and (where needed) consult local professionals, you should have no problem putting a tankless heater in your crawl space.

Code Conditions for Tankless Water Heaters in Crawl Spaces

While the code requirements mentioned here can be a helpful guide, to ensure that your heater complies with local regulations, I recommend checking out your local coding as well.

Access Requirements

According to Section M2801.4 of the IRC, you must ensure that the water heater (and its connections) is easily accessible for the purpose of observation, maintenance, service, and replacement.

This means that you should not have to remove any permanent fixtures, connections or pipes for other appliances, furniture, or other stored items in order to access the heater.

For appliances in underfloor spaces, like your crawl space, there are some specific requirements as per Section M1305.1.3 of the IRC:

Tankless Water Heater IRC Installation Guides in a Crawl Space;  IRC Section M2801.4
Tankless Water Heater IRC Installation Guides in a Crawl Space according to Section M2801.4
  • A level workspace of 30” deep by 30” wide is required around the control side of the heater.
  • There must be an unobstructed passageway big enough to remove the heater (or the largest appliance in the space). This passage is required at minimum to be 30” high and 22” wide.
  • There is a maximum distance of 20 ft allowed down the centerline of the passageway between the heater and the opening of the passageway.
  • The access opening must at minimum be 22” by 30” but must be big enough to remove the largest appliance.
  • You are going to need to line the walls of the passageway with concrete or masonry 4” above the adjoining grade should the service space or passageway depth fall 12” below this grade.

Thankfully, tankless water heaters are pretty compact and so are unlikely to make access difficult.

Related article: Is It OK To Store Things Near a Water Heater

Electrical Requirements

Section M1305.1.3.3 of the IRC, requires a light source near the appliance, with a switch at the access opening.

Additionally, you will have to install an electrical outlet in the crawl space to supply your tankless water heater.

Section M3803.11 of the IRC says cables and conductors must be installed in a raceway. Alternatively, the cable must be designed for direct burial or concrete encasement and one or more of the following factors applies:

  1. The metal cover is waterproof.
  2. A waterproof covering is put under the metal casing.
  3. The insulation covers under the metal casing are designed for wet locations.

Installation Requirements

Please take note that many manufacturers recommend that professionals install your tankless water heaters and apply this to the warranty.

Ground Clearance

IRC Section M1305.1.3.1 covers underground spaces for ground clearance. A level concrete slab (or approved material) is required if the appliance is supported from the ground and this slab must extend at least 3” above the ground and must comply with manufacturer recommendations.

If the appliance is suspended from the floor, there must be a ground clearance of at least 6”.

By elevating your heater, you keep it out of reach of animals, and it also prevents dirt from being sucked into your heater or onto the gas burners with combustion air. It also helps to keep air following freely and prevent your appliances from overheating.

Structural and Piping Protection for Freezing

Section P2603.5 of the IRC states that in areas where winter temperatures reach 30°F or lower, water piping is not permitted in crawl spaces without sufficient provision to protect it from freezing by heat, insulation, or both.

Libra Supply 3/4 inch IPS Isolator Tankless Water Heater Service Valve Kit – 3/4'' FNPT X FNPT Thread Brass Isolation Set with Pressure Relief Valve | Pipe Fittings, Supplies & Spare Parts

It further specifies:

“Water service pipe shall be installed not less than 12 inches (305 mm) deep and not less than 6 inches (152 mm) deep below the frost line.”

When water freezes in pipes it leads to cracking and bursting. This will result in having to repair and replace your water pipes. It’s going to save you a lot of hassle by taking the necessary steps to prevent it.

Otherwise, you are looking at potential structural damage due to leaking pipes and the fact that you are likely to be without hot water until the pipe is fixed!

Flood Protection

If you live in an area that experiences flooding, you are going to need to consider flood protection. The IRC provides the regulations for a flood-resistant installation of a water heater in Section R322.1.6.

Your heater and all of its components can be installed below the design flood elevation level for your area. However, in order for this to be allowed the tankless water heater must be designed and installed to:

  1. Prevent water from getting into and gathering in the appliance and its components.
  2. Resist the pressure of water at rest as well as the forces it can exert in the event of flooding as per ASCE 24 (minimum requirements for buildings and structures in flood hazard areas).

With a tankless water heater, you at least do not have the risk of the water in the tank becoming contaminated during a flood. So, as long as your electric and wiring systems are coded according to wet location regulations then it is permitted.

You will need to look at your local codes to confirm your flood-resistant installation.

Non-Code-Specified Considerations

How Hardy Are the Casing and Components?

If you are choosing to install your tankless water heater in your crawl space, then you will need to follow the necessary coding regulations for the installation, electrics, and freezing and flood protection.

Therefore, the casings and components should be durable so as to withstand the environment and climate.

They can even be installed in such a way as to survive both flooding and seismic movement. With the appropriate equipment and installation, this will prevent unnecessary damage to your water heater.

So, while there might need to be some routine replacing and repairing of the casings and components, a correctly coded and well-maintained tankless water heater should be pretty hardy.

Protect Your Pipes From Frost

So now we know that it is possible for your water heater pipes to freeze, I think it warrants a look at how to prevent it.

Insulate Your Pipes

Insulation is probably the best solution to frosty water pipes and it is pretty cheap.

Run Your Faucet

Even if it is just a drip, running out that cold water will get rid of the ice.

Heat Sections of Your Pipes

Apply heat until your water pressure has returned back to normal and you are good to go. You can do this by:

  1. Using a hairdryer.
  2. Using a space heater.
  3. Wrapping the pipes in hot and wet towels.
  4. Using an electric heating pad around the pipes.

Call a Plumber

When in doubt you can always call a professional.

If you want more information on this, I have written an article on the 12 tips to prevent pipes from freezing in your crawl space.

Tankless Vs Regular in the Crawl Space: Which Is Best?

Vector illustration of a set of gas water heater and electric water heater

Regular and tankless water heaters are governed by the same code regulations. This means that your decision to go with tankless or regular will depend on your personal preference and perhaps how easy each would make your installation process.

If you want to know about the installation process for a regular water heater in a crawl space, you can look at my article on Can You Put a Water Heater in a Crawl Space?

A tankless option is much smaller, making it convenient if your crawl space is on the smaller/shorter side. This way, your access and ground clearance regulations are less of an issue as you don’t have to contend with a storage tank.

Tankless heaters are also safer as they are less likely to damage your property with leaks. Although, you might need to upgrade your electrical system if you opt for an electric tankless heater as they require an average of 120 amp.

If you don’t want to have to keep hauling a water heater out of your crawl space to replace it, then you will be pleased to know that tankless heaters can last 5-10 years longer than storage tank versions.

Related article: Can a Water Heater Be Installed Horizontally


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