How many feet of 3 inch pipe does it take to hold five gallons of water?

Answer 1

First step is to calculate volume in the pipe.

The volume contained in a 5in diameter section of pipe that is 12in long can be calculated by multiplying the area of a 5in diameter circle by the length of the pipe, in this case 12in.

To determine the area of a circle you use the following formula:

Area = Pi x radius^2

Area of 5in circle = 3.14 x (2.5in)^2

Area of 5in circle = 19.6in^2

We then multiply this "cross sectional" area of the pipe by the length.

19.6in^2 x 12in = 235.2in^3

Wikipedia tells me that the volume of a US Gallon is 231in^3

To determine the number of gallons in the section of pipe we divide our calculated volume by the defined volume for a US Gallon. Notice the units are the same!

Volume in pipe/ Volume of US gallon = 235.2in^3/ 231in^3 = 1.018 Gallons

Answer 2

A 5/8" pipe must be 61.8 feet long to contain one US gallon of water.

Answer 3

A three-inch pipe needs to be 13.6 feet long to contain five gallons of water.