How do you measure the size of a pipe fitting

The size of a pipe fitting is typically measured in two key dimensions: the nominal pipe size (NPS) and the pipe thread size. These measurements are crucial for ensuring that a fitting is compatible with the pipes and other components in a piping system. Here's how to measure the size of a pipe fitting:

1. Nominal Pipe Size (NPS):

  - The NPS is a standard measurement used to specify the size of pipes and pipe fittings. It is expressed as a numerical value, such as 1/2", 3/4", 1", 2", and so on.

  - The NPS does not represent the actual outer or inner diameter of the pipe or fitting but is a designation used for reference.

  - To determine the NPS of a pipe fitting, look for markings or labels on the fitting, which often indicate the size in inches.

2. Pipe Thread Size:

  - For threaded pipe fittings, you need to determine the size of the threads on the fitting.

  - Common thread standards include National Pipe Thread (NPT) and British Standard Pipe (BSP), which have different thread profiles and measurements. The NPT thread standard is commonly used in the United States, while the BSP standard is used in many other countries.

  - To determine the thread size, you can use a thread pitch gauge or thread pitch caliper to measure the thread's outside diameter and the number of threads per inch (TPI).

It's important to note that the NPS and thread size are not the same. For example, a fitting labeled as 1" NPS may have different thread sizes and thread types, depending on the standards and variations used in different regions.

When selecting pipe fittings, it's essential to ensure compatibility between the fitting and the pipes or other components in your system. This involves matching both the NPS and the thread size. Fittings with the correct NPS but different thread types may not be compatible.

To avoid issues, it's a good practice to consult with a supplier or refer to product documentation to determine the specific size and thread type of a pipe fitting if it's not clearly labeled. Additionally, if you're replacing an existing fitting, it's advisable to bring the old fitting to a hardware store or consult with a professional to find an exact replacement.