The washing machine in my basement drains into this utility sink. On the end of the washing machine discharge, there is a lint catcher. Can anyone tell me what this white pipe is that comes up and is open at the top near the sewage stack? There is a bad sewage smell that comes out the top of this pipe and I'm wondering why this pipe is here and open? The p trap where the utility sink drains is supposed to leave water in there in order to prevent smells from coming back up, right? As a side note, the sink drains slow. It's hard to tell, but at least part of it seems to be from the small drain cap that I leave in when the washing machine drains. I've debated even if it would make sense to have the washing machine discharge directly into the sewage stack to avoid having to go through the utility sink altogether. I'm not sure why this wouldn't have been done in the first place either? The house is older, built in the 1950s.
I'm guessing that the white pipe you're referring to is the original drain for a washer. The extension piece fastened with duct tape might have been added because the washer draining caused some water to overflow out of the pipe.
The slow draining could be due to partial blockage. You might want to remove the trap and clean out the pipes. Scum can build up above the trap over the years and can smell. Try removing that extension piece and put the washer drain pipe, minus the lint catcher, into the pipe and see how it works out.