New construction water lines, should I use expansion on the fittings or should I crimp them?? And why- pros and cons of each. I have another question posted about proper sewer venting diagrams and information. I am currently getting ready to help a friend plumb his new construction home that he's and it's been several years since I've done plumbing for a living (a lifetime ago). CPVC was still the big thing when I quit plumbing and went to HVAC. Pex was just coming onto the scene, so I know very little. Any information is welcomed and greatly appreciated. I want to be able to --know-- beyond any doubt that I can help my friend and everything will work properly for the life of his new home.

  • Please revise and ask just one question per post, and make sure it's specific. Take the tour to learn more.
    – isherwood
    Commented Jun 24, 2018 at 17:23
  • I'm not sure what "use expansion" means.
    – isherwood
    Commented Jun 24, 2018 at 17:24

1 Answer 1


There are different types of PEX and different types of joining systems.

PEX A is joined by slipping a PEX collar around the PEX tubing, then temporarily expanding the end with the collar. Without delay the fitting is inserted and in a minute or two the PEX relaxes and grips the fitting. This type of fitting has a larger internal diameter than the fittings for the other types of PEX.

The other types of PEX are PEX B and PEX C. These latter two are joined without enlargement--a metal band is crimped in some systems and in other systems a metal band is simply pulled into place to secure the PEX tubing to the fitting. Each type has its strong points and weaker points.

One video https://www.youtube.com/watch?v=fhzIRHLOQ_E

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