Buoyancy refers to the upward force experienced by an object in a fluid, such as water. In water this force is proportional to the water displaced by the object. If this force is higher than the weight of the object, the object will float on the water. This effect allows the construction of boats and ships, which float even when they are made of heavy metals. The buoyancy of a pipe can be calculated using its diameter and length.
Multiply the outside pipe diameter in feet by itself using a calculator and call it "D." Assuming the diameter to be 1.5 feet, D = 1.5 X 1.5 = 2.25.
Multiply "D" with 62.4 (the weight of water in pounds-per-cubic-foot) and call it "D1." For the example being considered, D1 = D X 62.4 = 2.25 X 62.4 = 140.4.
Multiply "D1" with 0.78 (the percentage of the pipe which is submerged in the water) and call it "W." For the example being considered, W = D1 X 0.78 = 140.4 X 0.78 = 109.51.
Multiply "W" with the length of the pipe to get the required buoyant force in pounds. Assuming the length of the pipe to be 5 feet, the force will be F = W X 5 = 109.51 X 5 = 547.55 pounds.