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Can I install water heater in the crawl space by code?
Wednesday, February 16, 2022
The International Residential Code (IRC) allows water heater installation in a crawl space (an unconditioned space under a home, just a few feet high, and over bare dirt), but there are multiple requirements for the installation:
•• Water heater must be approved by manufacturer for crawl space installation (IRC M1302.1). For gas installation, there are no lowboy gas tank water heaters, so forget that; and tankless gas installation will require code-compliant flue to exterior.
•• Access opening and access-way through crawl space to appliance must be minimum of 22-inches wide by 30-inches high, clear of any obstructions, and also large enough to remove the water heater later. Cannot be more than 20-feet from access opening to appliance (IRC M1305.1).
•• Minimum 30-inches by 30-inches level working space in front of the control side to service the water heater (IRC M1305.1).
•• A luminaire (light fixture) near the water is necessary, controlled by a switch at the access opening (IRC M1305.1.3.1).
•• Also need a receptacle outlet near the water heater for service technician to use (IRC M1305.1.3.1).
•• Water heater must be 3-inches above ground if supported from below by concrete slab or other approved material. If water heater suspended above the ground, it must be minimum 6-inches off. (IRC M1305.1.3.1)
•• If the passageway or service space goes more than 12-inches below grade, a concrete or masonry lined passage must be installed for access (IRC 1305.1.4).
•• The water heater’s TPR (Temperature and Pressure Relief) valve must drain by gravity to a readily visible location outside the crawl space, along with multiple other requirements (IRC P2804). See our article What are the most common installation mistakes with water heater replacement? for more details.
These standards apply to both tank and tankless electric water heaters. Other concerns when installing a water heater in a crawl crawl space are protection from possible flooding after a rainstorm, accelerated corrosion due to high humidity, and protection of piping from freezing in colder climates.
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