120 Gallon Tank Propane Tank

About the 120 Gallon Tank

Small residential installations for homes with modest propane needs such as a water heater and cooking range only. Often installed at vacation homes, small cottages, or as supplemental supply for a single propane appliance. Requires professional installation and delivery service. Typically filled to 80% capacity (96 usable gallons) per safety regulations.

The 120 gallon tank measures 52 inches long x 30 inches diameter and has a total volume capacity of 120 gal. Per NFPA 58 safety regulations, propane tanks are filled to a maximum of 80% capacity to provide expansion space as the liquid propane warms and expands. This means the practical usable capacity per fill is 96 gal. At the national average price of $2.50 per gallon, a full fill costs approximately $240.00.

The 120 gallon tank requires professional installation on a level pad with adequate clearance from buildings, property lines, and ignition sources per local fire codes. Most municipalities require a minimum of 10 feet of clearance from any structure for tanks of this size. The tank can be installed above ground or, in some configurations, underground. Above-ground installation is less expensive but visible, while underground installation preserves yard aesthetics at additional cost.

How Long Does a 120 Gallon Tank Last?

The duration between fills depends entirely on your propane consumption rate, which varies by season, appliance mix, and climate. The table below shows how long a single fill of 96 gal would last for four common usage scenarios at the national average baseline.

Note that the "months per fill" figure represents an average across the entire year. During winter heating months, consumption can be 2-3 times the monthly average, meaning a full tank may last only 2-3 months during peak heating season. During summer, the same tank may last 6-12 months if heating is not needed. Plan your delivery schedule accordingly, and request delivery when your tank gauge reads 20-30% to avoid running empty.

Tank Size Comparison

Compare the 120 gallon tank to other standard propane tank sizes to determine if this is the right capacity for your needs. If your annual consumption is close to the boundary between two tank sizes, choosing the larger option provides a safety margin and reduces delivery frequency.

Safety and Maintenance

Propane tanks are designed for decades of safe service when properly maintained. Above-ground tanks should be visually inspected regularly for signs of rust, physical damage, or settling of the support base. The tank should be painted with a light, reflective color (white or light gray) to minimize heat absorption from sunlight, which reduces the pressure inside the tank and decreases the risk of the pressure relief valve activating.

Keep the area around the tank clear of vegetation, debris, and combustible materials for at least three feet in all directions. Ensure the tank's pressure relief valve, fill valve, and service valve are accessible and not obstructed. Never stack items against or on top of a propane tank. If you smell the distinctive rotten-egg odor of propane (added as a safety odorant called ethyl mercaptan), leave the area immediately, do not operate any electrical switches or flames, and call your propane company and the fire department from a safe distance.

Professional tanks (120 gal and larger) should be inspected by your propane company during regular deliveries. They check tank condition, fittings, and the regulator during each fill. The tank gauge should be verified for accuracy periodically. Underground tanks have additional inspection requirements for cathodic protection systems that prevent corrosion. Most propane companies include basic tank inspection as part of their delivery service.

Frequently Asked Questions