Happy New Year. I had a plumber come to install a drain for a utility sink in my garage. This is what he did. I'm not a plumber, but I thought that the sink drain had to run into a vertical drain. The drain stack is behind that wall stud, to the left of the fitting that he installed. The copper pipe running through the drywall is the drain from the bathroom sink. I asked him about the angling of the drain and he said that it didn't have to be angled. That doesn't seem consistent with what I've read, but again, I'm not a plumber. He told me to make a little riser for the plastic sink out of 2 x 4. Is this OK or do I have a problem? By the way, I figured out not to use the sink on the other side of the wall (he did not install the sink itself) before the sink is attached, but he never bothered to tell me not to.