There is a stand pipe that goes to the roof but it was capped in the wall where I believe it was originally vented. Is there a reason this was done. I did'nt have a problem with a slow drain before but am curious about why this was done. I do have a smell now with the current drain that I have. When I'm ready to install new sink, will it be all right to just go with the way it currently is used?

Your sink line needs to be vented, both for better draining and for sewer smell

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