Have you wondered what all the writing means on the exterior of PEX tubing? Well, on the exterior of all PEX tubing there is a required print stream that provides information about the design specifications and standards for the tubing. This consists of various codes that are approved by agencies, which ensures consistency between different manufacturers of PEX tubing.

*Note: the terms “tube”, “pipe”, “tubing” and “piping” are used interchangeably in this article.

1. Manufacturer

The first thing that appears in the PEX print stream is the manufacturer. This can be the manufacturer’s name, a product specific trade name and/or logo. In addition to this, the specific part number for the tubing application, size and coil length is also listed. This sequence of numbers varies with different manufacturers and may contain letters.

2. CSA and ASTM Standards

On all PEX tubing, there must be markings for various standards and testing agencies, which indicates that the tubing is approved for use under certain conditions. In Canada, these specifically will be Canadian Standards Association (CSA) and American Society for Testing and Materials (ASTM) standards listed. CSA B137.5 identifies that the tubing has been approved for use with typical pressure applications through testing in accordance with “Cross-linked Polyethylene (PEX) Tubing Systems for Pressure Applications”. Every style and brand of PEX or PE-RT for hydronic heating and plumbing applications must meet this standard.

There is greater variability in ASTM Standards.  The first listed will either be “F876” or “F876/ F877”. F876 is the Standard Specification for Crosslinked Polyethylene (PEX) Tubing and F877 is the Standard Specification for Crosslinked Polyethylene (PEX) Tubing Hot and Cold-Water Distribution. Following this, the ASTM codes for approved fitting systems listed. The codes for fitting types can include F1807, F2159, F2098, F1960, F2080 and/or F2854. These codes and their corresponding fitting processes can be further explored in the article, “What Are The Types of PEX Fittings?”.

3. NSF

The final testing body required in Canada is the National Sanitation Foundation (NSF).  You will find included on the print stream the NSF Mark for Toxicity & Performance Certification.  Without this listing a PEX/PE-RT manufacturer cannot legally sell their products in Canada or the United States for plumbing applications. NSF is a potable water listing that is followed by a code that indicates how well the tubing meets the lead requirements. For example, tubing that carries drinking water will have the code NSF-61-G. Other listings that can be included in the printing stream, some of which are Underwriters Laboratories (UL), Uniform Plumbing Code (UPC), and International Association of Plumbing and Mechanical Officials (IAPMO). It is not required for all of these agencies to be listed, and the selected agencies that are listed vary between different manufacturers.

4. SDR, CTS and Size

Following the testing standards a specific product adheres to will be a number of material property designations. The Standard Dimensional Ratio for Fitting Size Acceptance (SDR) must be listed. The number listed with SDR is a constant ratio of the tube’s outside diameter to average wall thickness, and roughly correlates inversely to the pipe’s ability to withstand internal pressure. A higher value indicates that the tubing can withstand lower pressures and a lower value indicates that the tubing can withstand higher pressures. Following this, there must be information that indicates the size of the tubing. This appears on the tubing as a measurement in inches followed by the letters “CTS” which stands for Copper Tube Size and gives the nominal tube size. There is an option of an additional measurement that follows with the letters “OD”, which indicates the tube’s Outside Diameter.

5. Material Designation Code

The Material Designation Code consists of four digits that follow the material (PEX). The first digit refers to the chlorine resistance of the PEX piping, 5 being the highest and 0 the lowest in regards to meeting the ASTM F876 – Standard Specification for Cross-linked Polyethylene (PEX) Tubing requirements. The corresponding test method for chlorine resistance is F2023 (Standard Test Method for Evaluating the Oxidative Resistance of PEX Tubing and Systems). A 0 identifies that the tubing has not been tested for chlorine resistance. A 1 signifies that the tubing meets the F876 requirements at 25% at 140 °F (60 °C) and 75% at 73 °F (23 °C). The number 3 indicates that the tubing meets the F876 requirements at 50% at 140 °F (60 °C) and 75% at 73 °F (23 °C). Finally, a 5 signifies that the tubing always meets the F876 requirements at 140 °F (60 °C). The numbers 2 and 4 are reserved for future applications.

The second digit in the designation code identifies the tubing’s UV resistance level. PEX tubing is affected by UV through exposure to sunlight. PEX should not be stored or installed outdoors. This digit corresponds with the test method F2657 (Standard Test Method for Outdoor Weathering Exposure of PEX Tubing). A 0 indicates that the tubing has not been tested or does not meet the requirements. A 1 indicates that the tubing meets the requirements for exposure for one month, 2 corresponds to a three months exposure rating and 3 indicates a six months exposure rating. The hydrostatic design stress (HDS) for water at 73 °F (23 °C) is indicated by the third and fourth digits in the code sequence. The units are measured in 100 psi and any decimal figure is dropped. For example, if the third and fourth digits read “08” then the HDS is 08 x 100 psi or 800 psi.

6. Pressure Rating

On the print stream, there will also be a standardized pressure rating listed. This appears as a value in psi, followed by a temperature in Fahrenheit (160 psi @73 °F).  It is important to note that this is a standardized minimum rating and certain styles or brands of PEX piping may have capabilities which exceed this listing.

7. Country of Origin, Date/Time Stamp and Length Marking

Finally, the PEX tubing will also have the country of origin printed on it, as well as a date and time stamp. This will appear in a format such as “Made in the USA 02/07/2016 11.03”. Optionally PEX piping may include regular length markings each 3-5 ft.  This is most commonly found on oxygen barrier piping for radiant hydronic applications, where it is important to know how long each piping run is.

It is extremely important to understand the print stream, as it provides valuable information needed to create systems with PEX tubing. The codes and abbreviations that have been listed and discussed are standardized to provide clarity when identifying specifications for PEX tubing. For further inquiries, our design and engineering team can be contacted.



AWWA C904 Subcommittee of the Standards Committee on Polyolefin Pressure Pipe and Fittings. “Committee Report: Design and Installation of Cross-Linked Polyethylene (PEX) Pipe in Accordance with AWWA C904.” Journal (American Water Works Association), vol. 104, no. 3, 2012, pp. 68–79. JSTOR,

www.jstor.org/stable/jamewatworass.104.3.68. Accessed 1 Mar. 2021.


CANARSEE. “PEX Pipe Markings.” Canarsee, 20 June 2016,



DESIGN GUIDE Residential PEX Water Supply Plumbing Systems. second ed., Home Innovation Research Labs, Inc., Plastics Pipe Institute, Plastic Pipe and Fittings Association., 2013.