To measure PVC drain pipe sizes, wrap a string around the pipe, and then measure the string to arrive at the pipe's circumference, notes IrrigationTutorials.com. Compare the string circumference to the table listed on the website to find the size of pipe; for example, if the string measures 3.25 inches, then it is a 3/4-inch pipe.
When measuring pipes, strip away insulation surrounding them. Do not factor it into the measurement of the pipe's circumference, suggests IrrigationTutorials.com. To measure the pipe, follow the steps below.
- Cut a string
- Prepare the pipe for measurement and measure
- Compare the measurement to the website's table
Cut a string to a length of six inches to use to measure the pipe.
Strip away any insulation surrounding the pipe. The insulation interferes with proper measurement and should not be included in the measurement of the pipe's circumference. Wrap the string around the pipe, holding a finger on the string to indicate how long it is. Measure the length with a ruler or measuring tape.
Compare the measurement to the "For Steel Pipe and PVC Plastic Pipe" chart on the IrrigationTutorials.com website. A four-inch string length indicates a one-inch pipe, a five-inch string indicates a 1 1/4-inch pipe, and a six-inch string indicates a 1 1/2-inch pipe. Keep in mind that the length of the string may vary slightly from the lengths on the chart, due to factors, such as measuring accuracy, pipe manufacturer and other factors.