Securing a wobbly PVC stack

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by penobscotman, Mar 18, 2013.

  1. penobscotman

    penobscotman Member

    Messages:
    30
    Location:
    Buffalo NY
    I just cut the last bit of CI out of my 4 inch stack, replacing it with PVC joined with Fernco sleeves. Now there is a bit of wobble that wasn't present when the CI was locked with riser clamps. I haven't yet connected branch lines to the stack and I expect that these will reduce the wobble. But until then is there some way of clamping/securing the PVC stack? I assume that the iron riser clamps are inappropriate.
  2. kreemoweet

    kreemoweet New Member

    Messages:
    371
    Location:
    Seattle. WA
    There's nothing inappropriate about riser clamps on PVC.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,360
    Location:
    Yakima WA
    One thing that may be part of the problem is the "Fernco sleeves" you used to connect the PVC. Typically, the term "sleeves" implies the neoprene sleeves that are clamped on each end with a hose clamp. These sleeves are not code for above ground use for the very problem you are having. They do not provide a ridged connection. The proper sleeved connectors are called "banded couplers" which have a solid clamp the full length of the sleeve. By the way, "Fernco" is a brand name and applies to all sorts of connectors made by Fernco. All of that said, you still should use riser clamps to firm up the pipes.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    Now you know why "Fernco" sleeves are NOT allowed inside the building, either under the floor or above it. Use ProFlex, (not No-Hub couplings), or similar "banded" couplings and the riser will be rigid.
  5. penobscotman

    penobscotman Member

    Messages:
    30
    Location:
    Buffalo NY
    Thanks for all the replies. I will replace the flexible (that's the problem!) couplings with the rigid banded couplings. I looked at both at HD, and it seemed to me that the flexible couplings, with 4 inches top to bottom had more bearing surface than the the banded couplings. I need to go to a real plumbers's supply.

    So it's OK to use iron rider clamps? There is no danger of over-tightening and shattering the PVC?
  6. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    The clamp only needs to be tight enough to hold the stack. If you don't over-tighten it, there is no danger.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    The rubber couplings only "bearing surface" is the area UNDER the clamps, which is relatively small. You could use a 2" long hose and get the same "bearing surface" and maybe more rigidity because of less area to "flex". Do not use N0-Hub couplings because the PVC pipe is slightly larger and the couplings have to "distort" to stretch over it. Use couplings specified for, made to, the size of the PVC.
  8. penobscotman

    penobscotman Member

    Messages:
    30
    Location:
    Buffalo NY
    Thanks to all who responded. I did what you said - proper Fernco shielded fitting, gently tightened riser clamp and now everything seems nice and rigid.
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