Offseting waste stack

BordlAugust 31, 2011

Can the waste stack be offset after the branches tie in? I would like to run a waste stack from the second floor through the slab to the building sewer.

My builder says this cannot be done because a column footer is in the way. As a result of the footing the stack must enter the slab 12" away from where it will run on the first and second floors.

Can this offset be done? And, if so how far does the offset start from the last branch fitting entering the stack?

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If your under the IRC you may not have an offset on a vertical waste stack...REf. IRC-3109.2

    Bookmark   August 31, 2011 at 1:06PM
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lazypup, if the offset could be done with two 22 1/2 elbows over some distance from the slab to the next level, would that meet the code definition of vertical?

    Bookmark   August 31, 2011 at 6:52PM
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Any angle greater than 45 degrees would be defined as vertical, however the code says "NO OFFSET" on a vertical waste stack.

    Bookmark   August 31, 2011 at 7:49PM
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My suggestion to the homeowner is to first ask his plumber. We do not know for certain which code applies in his jurisdiction. And the plumber could ask the inspector if necessary. The builder may not know much about the plumbing code. In NC, the basic code is the IPC , but the State has made numerous amendments and even publishes it with those as their own code. Their Section 710.1.2 in the 2009 edition does permit offsets in vertical stacks if sized per a couple of referenced sections. The applicable code in this instance may permit the offsets- or may not.

    Bookmark   August 31, 2011 at 9:31PM
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The IPC does permit an offset in a vertical stack,,but a vertical stack is not necessarily a waste stack....

    Bookmark   August 31, 2011 at 9:52PM
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Maybe I am not using the correct terminology. The reason I ask is on the other end of our house this was done and inspected.

A cast iron pipe rises out of the slab, continues 6" vertically to a 3" copper clean out, another 6" to a pair of 45 degree bends separated by 14" of pipe and then vertically to a number of branch connections. The net result is the stack exits the slab about 16" from the wall and then the stack runs against the wall. Is this setup in violation of IRC code?

If we can do the same thing with the other stack then we can significantly increase the size of our family room.

    Bookmark   September 1, 2011 at 9:57PM
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