I see. This house is pier and beam so can I add the cleanout under the floor where it slopes toward the main drain? This way I don't have to create an access panel and move the vanity if I need to snake it?? Also, the drain lines from the sink to the double fitting, should they be sloped .25" per foot? I keep seeing examples online and some appear to be level, with no slope. The old drain from the sink that I am tearing out, opposite wall, doesn't have a slope on it. It's flat and tees into the vent pipe that is shared with the toilet. ?? What do you say?