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  1. #1
    Join Date
    Jul 2011
    Posts
    7

    Confused Rusted Ductwork in Concrete Slab

    Hi,
    I just had my ducts cleaned (sort of) and discovered that the ductwork is rusted and crumbling in the portion of my house that is on a concrete slab. There is alot of dust (concrete?) in the ductwork and the cleaners could not get it out. They said it just kept coming. Any advice on how to clean and retrofit plastic ductwork into the space OR do we have to get an entirely new system through the attic?
    DESPERATELY NEED HELP..
    Pat

  2. #2
    Join Date
    Jan 2007
    Location
    N.E. Ok.
    Posts
    1,371
    It is best to go with new ducts in the attic when you have that option.

  3. #3
    Join Date
    Feb 2010
    Location
    Ontario Canada
    Posts
    1,341
    Just a crazy idea here, I know that older drains (clay tiles) can crack and cause problems. One of the solutions out there now is to have the tile coated on the inside. A company sends a cable down the pipe and it sprays a coating on the inside of the pipe and makes it water tight again.
    They may be able to do this to your duct work. It might be worth phoning around to drain companies that do this type of work and see if they think it is feasible.
    Good luck
    Never give up; Never surrender!

  4. #4
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,198

    If you are in a heat dominate area

    Then you are going to need to balance the value of low supply diffusors and perhaps some concrete dust with the inefficiency of having un-insulated ducts!

    If you are not in a heat dominate area then installing new duct on the perimeter of your home ( inside the building envelope) and then enclosing these ducts in drywall soffits is your answer.

    Hard to believe you have slab on grade in a heating dominate area. Where are you
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  5. #5
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,603
    Are you using the gal. metal ductwork inside the cement floor for discharge air? If so, where is your return air ductwork located?

  6. #6
    Join Date
    Jul 2011
    Posts
    354

    Unhappy

    that is a OLD set up. bite the bullet you need a new duct sytem! good luck$$$$$$$$$$.

  7. #7
    Join Date
    Jul 2011
    Posts
    7
    Thanks to those of you who gave me some ideas. I live in Albany, NY so we use the heat and/or the A/C most of the year. The system is functioning fine (although now I realize some of the blowing capacity is probably compromised). If we get a whole new system with ductwork through attic, do we need to seal up the old ductwork? Anyone have a recommendation in the Albany, NY area that is reputable and reasonable that does this kind of work?
    Thanks again for all of your help.

  8. #8
    Join Date
    Jul 2011
    Posts
    7
    I am not sure what I have. The returns are all on the wall, the supplys are all in the floor, so I think the returns are fine, just the supplys are rusted out and disintegrating. At least that is the way it appears from looking in throught the floor registers and about 3 feet in through the basement ducts.

  9. #9
    Join Date
    Jul 2011
    Posts
    354

    Hmm

    just so you know, there are a lot of systems out there like that, usually over MANY years they get the same results you got. i'd seal up the ducts if you do the attic system!

  10. #10
    Join Date
    Jan 2007
    Location
    N.E. Ok.
    Posts
    1,371
    I live in rusted slab duct capital of the U.S.A.
    I have just about seen it all. Seal the ducts with concrete install new equipment and duct work and be done with it.
    You won't be able to sell the house to anyone that requires a mortgage, lender will deny untill fixed.

  11. #11
    Join Date
    Jul 2011
    Posts
    7
    Has anyone heard of DST? Duct Seal Technologies for this type of problem. Not sure it would work if the ducts have disintegrated.

  12. #12
    Join Date
    Jan 2007
    Location
    N.E. Ok.
    Posts
    1,371
    Have you had a camera run through and confirmed the duct is still intact?
    It works if not rusted out.
    The problem is metal duct was to be encased in concrete 2" thick min. A lot of the times the concrete slump was to dry to evenly flow around the pipe which leaves voids at the bottom, this is where coatings have problems there is no pipe or concrete to coat.

    Mclean out of Tulsa,Ok. claims they can build up rusted out ducts with a duct sealant process before coating, i have no knowledge if it works.

  13. #13
    Join Date
    Jul 2011
    Posts
    7

    Thanks Captube

    We have not had a camera, but thinking about doing that. I suspect there is severe rusting and disintegration based on looking at the first 3 feet I could see into the supply when they did the vent cleaning, but I could be wrong. I guess that will be our next step and then decide what to do. If everything is disintegrated and vacumed out, can you just run the heat and air through the concrete opening that is left? OR run some other flexible ducting through the opening? My heat and A/C seem to be functioning fine at the moment (even better after the duct cleaning).
    Thanks again for your input.
    Desperate in Albany, NY!!

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