Determine the Size of the Pipe

Suggested Items

• Digital Caliper (Most accurate way to measure a pipe)
• Ruler or tape measure with inches 
• Small piece of string and a sharpie (recommended if you do not have a caliper)

Overview

Accurately measuring the size of the pipe and determining the pipe material will allow Hydropoint to prepare and calibrate the flow monitor to specification. Water pipes in the United States commonly coming in 1/2", 3/4" and 1" sizes, referred to as "nominal pipe size". The nominal pipe size does not correspond to an actual measurement outside of the pipe. You'll need to measure either the diameter of the pipe or the circumference. Compare this measurement to the table at the bottom of the article to determine pipe size. 

There are a few easy ways to measure the diameter or the circumference of the pipe. Each method for measuring the pipe is described below. 

Methods for Measuring the Pipe

Digital Caliper (Preferred Method):

Measure the pipe with a digital caliper. A digital caliper is the easiest and most accurate way to measure a pipe. 

Tape Measure or Ruler:

Hold a tape measure or ruler up to the pipe to measure the diameter. This can be tricky, but the pipe types are different enough that it should be possible to size the pipe this way. See chart at the bottom of this article for expected measurements when using a tape measure or ruler. 

String Measurement:

If all else fails, you can measure the circumference of the pipe by holding a string around the pipe. Make a mark on the string where it comes all the way around the pipe. Measure the string with a tape measure or ruler. 

• Step 1: Wrap string around the pipe and mark it

• Step 2: Measure from the end of the string to your marking 

Measurement Verification 

Use the actual measurement(s) you just made to determine the pipe size with the tables listed below. 

Note: You'll need to know the pipe material as well. If you do not already know this, please refer to the KB article for How to Determine Pipe Material.

Copper, CPVC & PEX Pipe Sizes (aka CTS)

PVC Pipe Sizes (aka Schedule 40)

In summary, there are several methods that can be used to accurately measure the outside diameter of a pipe. The best and most accurate method is a caliper. Once the pipe material and pipe size for each monitor point location has been submitted, HPDS will provide a quote for the flow monitor required for each location point. To determine the pipe material, please see KB article How to Determine Pipe Material.

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