A tiny bit of rust in a new CI tub

Discussion in 'Shower & bathtub Forum & Blog' started by David Meiland, Nov 3, 2008.

  1. David Meiland

    David Meiland General Contractor

    Messages:
    16
    Location:
    Friday Harbor, Washington
    Tub is a Kohler Maestro cast iron drop-in, white. It sat outside my plumber's shop for a month or so in its crate, then we moved it to the job where it was inside, uncrated, and in perfect condition--I checked it carefully (I'm the GC). We installed it by lowering with an air bag due to a tight alcove and no way to manhandle it.

    Owner uses it once, to give the dog a bath no less. Later on I am crawling around in the bathroom doing some caulking and I notice a tiny little "spider" of rust in the bottom. Very small but it's there, and it's under the glaze, it won't rub off. My assumption is that the glaze has a pinhole or some crazing at this spot and the first use of the tub has caused the casting to start rusting.

    I assume we need to remove this tub and replace it. If it were acrylic I might hope for a patch in place, but it doesn't seem likely with a glossy enamel item like this.

    Any thoughts?
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I believe Kohler would deal with this in place. Go through your distributor and get a hold of the Kohler rep.
  3. David Meiland

    David Meiland General Contractor

    Messages:
    16
    Location:
    Friday Harbor, Washington
    The plumber is dealing with Kohler on it, and he seems to feel a new tub is the right call.

    How good would a patch or repair on a tub like this be? And, what are the chances that where there's one problem there's more? Maybe I ought to have the owner fill the tub and leave it a couple of days.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,519
    Location:
    Cave Creek, Arizona
    tub

    Filling the tub with water will not reveal any problem. What will eventually happen is that the rust will continue and eventually create enough pressure to pop the enamel from the bottom of the tub. A fixture refinisher might chip it out and restore the finish, but replacing the tub is the safest way, even though Kohler will only replace the tub. Installing it would not be covered.
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I have not experienced this....so I am just postulating. I know if you fine sand a piece of wood with 4/0 steel wool, then use a water based varnish over it....you can get rust stains in the finish. Is it possible that a tiny fleck of metal filing got imbedded in the final porcelain finish? My point on this is that in that case it is "surface" and not something which would continue to rust through to the iron. I guess this is something which it would not be worthwhile to chance.


    It sounds like Kohler and the plumber on scene are working this out, and I would respect whatever judgement they make.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,519
    Location:
    Cave Creek, Arizona
    rust

    The tub's finish is impermeable so steel wool fibers would not stick to it.
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