Propane: Definition & Technical Guide
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Propane is a three-carbon hydrocarbon gas (C3H8) stored as a liquefied petroleum gas (LPG) and used as a fuel source for water heaters, cooking ranges, pool heaters, fireplaces, and whole-house generators in residential properties not connected to natural gas utility lines. Propane delivers approximately 2,516 BTUs per cubic foot, nearly two and a half times the energy density of natural gas, and is stored in pressurized tanks on the property rather than delivered through underground utility mains.
LPG Storage, Mercaptan Odorant & Heavier-Than-Air Accumulation Risks
Propane is a byproduct of natural gas processing and petroleum refining. In its raw state, it is odorless and colorless, so manufacturers add ethyl mercaptan to give it a detectable sulfur-like smell for leak identification. Natural gas uses similar mercaptan odorants, though the specific compounds may differ by utility. Propane is heavier than air with a specific gravity of approximately 1.52, meaning leaked propane sinks and accumulates in low-lying areas such as basements, crawl spaces, and trenches, creating explosion hazards that differ from natural gas behavior.
Residential propane systems consist of an outdoor storage tank (typically 120 to 1,000 gallons), a pressure regulator that reduces tank pressure from approximately 200 psi to a usable 11 inches of water column (0.4 psi) for residential appliances, and a distribution piping system that delivers fuel to each appliance. The piping system uses the same materials approved for natural gas, including black iron, copper (in some jurisdictions), and CSST.
Propane is commonly used in areas without natural gas service, particularly in rural and semi-rural locations. Propane water heaters, pool heaters, and backup generators are common installations where natural gas infrastructure is unavailable or where homeowners prefer the independence of on-site fuel storage.
Above-Ground Tanks, Underground Tanks & Propane-Air Mixing Systems
Above-ground propane tanks range from 120 to 1,000 gallons and sit on concrete pads in the yard. They are less expensive to install but must meet setback requirements from buildings and property lines specified by NFPA 58.
Underground propane tanks are buried with only the access dome visible at grade. They preserve yard aesthetics but require cathodic protection to prevent tank corrosion and are more expensive to install and service.
Propane cylinders (20 to 100 pounds) are portable tanks used for gas grills, supplemental space heaters, and temporary installations. They are refilled or exchanged at retail locations.
Propane-air mixing systems blend propane with air to simulate natural gas pressure and BTU characteristics, allowing natural gas appliances to operate on propane without modification. These are used in large developments transitioning to natural gas service.
Gas Line Installation, BTU Sizing & Appliance Conversion Services
Propane gas piping installation and appliance connections are licensed plumbing work. Bonded Plumbworks’ gas line services include new propane piping installations, tank-to-appliance connections, pressure testing, and appliance conversions between natural gas and propane.
When homeowners add propane-fueled appliances such as tankless water heaters or pool heaters, Bonded Plumbworks sizes the piping system to handle the total BTU demand, installs appropriate regulators, and performs leak testing on all connections before placing the system in service.
NFPA 58, NFPA 54 & State Fuel Gas Code Requirements
NFPA 58 (Liquefied Petroleum Gas Code) governs propane storage, handling, and transportation. NFPA 54 (National Fuel Gas Code) governs propane piping within buildings. The applicable state building codes, Fuel Gas section, adopts both standards with state-specific amendments. Tank setback distances, regulator placement, and piping material requirements are all specified in these codes. Most states require licensed plumbing or gas contractors for all propane piping work.
Rinnai, Rheem, Gastite & AmeriGas Propane Systems
Rinnai manufactures propane-compatible tankless water heaters with factory LP conversion kits. Rheem and A.O. Smith produce propane tank and tankless water heaters. Gastite and TracPipe produce CSST certified for propane distribution. AmeriGas and Suburban Propane are major propane delivery providers serving residential and commercial customers nationwide.