Per the attached picture, I’d like to put in a double vanity sink about where the red spot is and hook up to existing plumbing. I see other examples but I just want to use my exact situation. Can I just tie into existing horizontal, run the second line lower over to the existing Drain/Vent line (blue line) or do I need to add a vent line up to 42” and over to existing? Any help is greatly appreciated.
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