Trying to prove this point to myself and others, I asked Claude to tell me how to add a drain line for a robot vacuum to the wash room sink.
Claude told me to drill a hole into the trap arm and add the line there. Which would, in case you’re not aware, be the worst place to put it. You never do this.
Drain lines get added to the tail pipe coming down from the sink, because if you add it to the trap arm (from the p-trap to the wall) you bypass the water seal keeping sewer gasses from infiltrating your home.