PVC Primer and cement question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by walkman, May 16, 2011.

  1. walkman

    walkman New Member

    Messages:
    26
    Location:
    San Diego
    How much time between applying primer and cement is acceptable?

    Should cement be applied to pipe AND fitting or is one of them only okay?
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,279
    Location:
    Land of Cheese
    All surfaces should be lightly coated. There is no waiting. First prime the section your are joining and then cement it.

    I cement the pipe, then the fitting, and then hit the pipe lightly one more time before joining.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,318
    Location:
    New England
    Keep in mind that a PVC joint is actually a solvent welded joint...the materials melt and when the solvent evaporates, they literally become one. The primer does several things: cleans any contaminats from the surface and starts to melt the surface and prepares it to be further disolved by the cement. The cement, by itself, may not penetrate the surface layer to make a good joint without the primer getting it started.

    So, yes, you do need both the primer and the cement to make a good joint. In many places, the inspectors look for the characteristic purple color of the primer or they'll fail the installation. They do make clear primer, but it's not good in areas where the inspector is looking for the purple stain! (it is a lot neater, as a drip doesn't stain things, though).
  4. walkman

    walkman New Member

    Messages:
    26
    Location:
    San Diego
    I've read different things about whether the primer should be wet or dry. So I was wondering if I could apply primer to several joints at a time to speed things up and then cement them 5-20 minutes later.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,255
    Location:
    Cave Creek, Arizona
    Do one joint at a time. It is best if BOTH are wet when the joint is made. As stated in the instructions on the cans.
    Last edited: May 17, 2011
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