PEX tubing is also sometimes referred to as PEX pipe, but the terms are interchangeable. While the most common type of PEX sold is marked as CTS-OD for copper tubing size, outside diameter, the second most common type of PEX, is marked IPS-ID for iron pipe size, inside diameter. Iron pipe size PEX for residential use also comes in sizes ranging from 3/8 inch to 1 inch. The mark for size on both types of PEX is located on the outside of the tube.
Charts for PEX tube fitting, tools and compatibility are available at PEXinfo.com.Learn more about Plumbing