As a part of a larger job, I have a plumber replacing water lines. He is going to use PEX. I read that sunlight exposure causes PEX to become brittle very quickly (on the order of a couple of weeks). Based on the I-know-it-all attitude that the plumber has showed on other parts of the project, I am worried that he might have stored the pipe improperly. Is there a way for me to check the state of the pipe before the walls are closed?

  • I don’t know if there is a test for pex UV exposure. I’ve read 30 days is enough to cause harm. If your plumber brought the pipe to the job in cardboard boxes it probably was stored correctly.
    – Kris
    Aug 10, 2019 at 14:45
  • diy.stackexchange.com/q/67214/46271. Related
    – Kris
    Aug 14, 2019 at 11:49

1 Answer 1


Most water PEX pipe has a UV stable outer coating.

Check the brand and spec sheets. If it is UV stable, its fine unless the sheath is cut or damaged.

NOTE: gas PEX does not have this coating.

  • The UV coating is only meant for 30-60 days protection
    – Kris
    Aug 17, 2019 at 13:47

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