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underground ductwork

zepfanzepfan Member Posts: 229
does anyone know what type of ductwork is suitable to be installed in the slab (underground) we have a job that we have given them a price on transient ductwork (plastic duct with a lining on the outside that is made to go in the ground) the customer balked at that price and the builder is saying that that type of duct is not needed and regular sheet metal duct is ok.i have told them that i do not feel comfortable installing anything but the plastic ductwork,because once it is in the slab,there is no turning back.i have also gone back on jobs with regular duct underground where it has filled up with water.i can't find anything in the international mechanical code that addresses this,and did not know if anyone knew of an ashrae standard for this.any assistance would be very helpful. thanks to all.


  • pipekingpipeking Member Posts: 252

    can u put regular galvanized sheet metal ductwork underground!!! it has to have an impermeable membrane. do not do that, it will kill!! get some literature on poly duct work and give it to the home owner, one they find out that it will cause and infectious environment in a matter of months, they will opt for the right way of doing it. and if not, leave! no amount off money is worth the health off someone.
  • Jamie HallJamie Hall Member Posts: 6,708
    I'm not sure about code issues...

    but sheet metal ductwork either in the ground or in direct contact with concrete isn't going to last long.  A few years if you are lucky.  Go with the Transite or even large diameter poly or ABS pipe (you don't say what the duct is for).

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • pipekingpipeking Member Posts: 252
    what is the duct being used for?

    i don't know the prices off hand between transient duct and plastic sewer pipe cuz u can use that. I've used it for vacuum ventilation underground be4 but it was 4", if u have to go bigger obviously the price might not be economical. also the amount of excavation for a large round pipe might not be feasible and a rectangle duct would be more feasible. also you know when u use a product that is designed for a specific use you won't have any problems.
  • zepfanzepfan Member Posts: 229

    thanks to all. the duct is being used for supply air from a gas fired furnace into an addition on a house.i found it in the imc code 603.8,i am going to make a copy of this part of the code,and send to the builder,and then i will get a cutsheet on the duct to show the homeowner that this is the only thing that can be used in the this point i would rather lose the job,then do something that is going to cause a code or health are right there is no amount of money worth that as there is always another job to do. thanks again
  • David MeilandDavid Meiland Member Posts: 12
    This might work

    but I doubt it will help get the price down
  • pipekingpipeking Member Posts: 252

    if it's getting inspected then there is know way that the builder could do it. you know some people try and sneak things in and also not pull permits. my whole thing is it's not safe, at all.
  • tim smithtim smith Member Posts: 2,226
    Underground duct

    Spundstrand is the standard of the industry for underground but wow get the check book out. It is a great product although and fits the bill. Good luck
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