A vertical 120-gallon propane tank is 55 inches tall and 30 inches in diameter, whereas a horizontal tank of the same capacity is 24 inches in diameter and 66 inches long. A 120-gallon tank holds 96 gallons of propane to allow for expansion.
The empty weight of a vertical tank this size is 175 pounds, and the full weight is 600 pounds. A horizontal 120-gallon tank weighs 300 pounds empty and 725 pounds full.
These tanks supply gas for appliances such as water heaters, clothes dryers, space heaters and kitchen ranges. Propane tanks are usually installed next to a building, at least 10 feet away from any electric ignition source to prevent fires.