How to Measure Water Flow Through a Pipe
- 1). Calculate water flow by measuring the pipe's discharge when it is flowing at full blast. According to the Oregon State University extension service, measure the horizontal point where the water's vertical drop hits 13 inches. Measure the diameter of the pipe. Multiply the pipe's inside area in square inches by the horizontal distance in inches. Multiply this result by 3.16. Divide the result by the square root of 13. You may also use common reference tables, such as those provided by OSU (see link in References).
- 2). Measure water flow through a pipe that is flowing at less than full blast by calculating the ratio of the unfilled portion of the pipe to the diameter of the pipe--e.g., divide the measurement of the unfilled portion by the diameter of the pipe. Multiply the inside area of the pipe in square inches by the horizontal distance in inches, then multiply that result by the ratio of unfilled pipe to total diameter. Multiply this result by 3.16, and divide the result by the square root of 13. Reference charts such as the one provided by OSU make this calculation easier (link in References).
- 3). Calculate water flow through a pipe using the easiest way, according to both Math Forum experts at Drexel University and by OSU extension staff--use timed volume. Take a stopwatch or timer and measure how long the water flowing from the pipe takes to fill a 5-gallon bucket. Divide the volume (5 gallons) by the time. Measure time in minutes, unless the flow is very fast; if this is the case, measure in seconds but convert the final calculation to minutes, as scientists express water flow in gallons per minute.
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