When Should You NOT Use PEX?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Verdeboy, Apr 19, 2007.

  1. Verdeboy

    Verdeboy In the Trades

    Can you use PEX to replace any water supply line, be it PVC, CPVC, Copper, PB, or Galvanized? Does it only replace 1/2" diameter pipe or other sizes as well? Can it be hidden in a wall, under a floor, etc..

    Is it okay to use compression fittings rather than the expensive crimper? If so, do you need to use the big, fat Qest fittings or are there smaller ones that are acceptable?
  2. Terry

    Terry Administrator Staff Member

    Bothell, Washington
    Not use PEX?
    Edited after reading hj's post below, Where there is a concern about fire in commercial buildings, it might not be approved.

    I do prefer copper for tub and shower valves, for strapping and stiffness.
    I think if you are thinking about using it though, you will need to pick a brand, and stock the fittings and tools for that.
    Last edited: Apr 20, 2007
  3. I think that applies to residential. In commercial or industrial buildings is it permitted?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    Usually not in commercial and industrial buildings, either because of codes, architectural preferences, or fire restrictions, among other reasons.
  5. Verdeboy

    Verdeboy In the Trades

    More PEX Questions

    Is it okay to connect PEX to the flex copper used in the inlet and outlet to a hot water tank?

    I've been researching PEX a bit and find that the most common system uses brass PEX fittings with copper crimp rings. Less common are the stainless steel clamps. You can also use "push-fits" and a variety of compression fittings.

    Do you all have any preference between the crimp rings and SSC's?

    It seems like the only brand they carry around here is by Zurn.
  6. Cass

    Cass Plumber

    If you were raising rats or chinchillas and the piping was exposed.
  7. pex for the economics...

    Pex is here to stay......

    basicaly it looks sloppy, but it is cheap...

    and it can be installed by any moron
    with a crimping tool, a hammer and cutter...

    when copper sits at 365 a pound....
    I suppose anything goes to keep
    the construction industry going....

    I certainly would not install it in
    commercial buildings, but in your average
    crawl space it will work for teh one year warranty
    expected by builders, and it might last as
    long as 25 or so years...

  8. one more place not to use pex, in residential, is where hot water comes out of the HW heater. That is what I've been told by people who claim to know. They say a minimum of three feet of copper first, and then switch to pex there or later. I wonder if this is really just a rule of thumb and not written anywhere. It seems they are concerned about the connection with the HW heater, leaving pex permanently heated by its contact with the HW heater. If 140 degree HW were too hot for pex to handle safely in the long term, then after it cooled off for three feet its temperature still wouldn't have dropped by much.

  9. kordts

    kordts In the Trades

    exurban Chicago
    Illinois code sez that the first 18 inches off a heater must be metal. Why? I just today changed a 15 year old water heater done in CPVC, all the way to the heater. The CPVC was fine. Even though I inspect some times, when I do water heater changeouts that are in CPVC, I violate the code. I use unions that are female brass and CPVC, right out of the heater.
  10. obviously an owner occupied house is "residential" but where is the dividing line where Pex is not allowed? In big cities there are duplexes, tripexes, quad, 8-plex, etc, and then condos, wood frame low rise and concrete high rise.

    At a certain point the building is deemed commercial / industrial even though it is residential. Is that dividing line the same everywhere? Pex not being allowed in commercial or industrial buildings, and thus not in residential buildings deemed "commercial industrial".

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