Plumbing gurus... I'm planning on running a 3/4 pvc condensate line for a new HVAC unit into my tub drain (currently old brass fittings) . I purchased an adapter at fergusons which i can put in between the the tub waste tee and the overflow pipe that also has an inlet that will accept a 3/4 pipe. ( I was trying to find a picture online to make the description more clear but cant find one). My question is, if I use this setup and I later have a backup in the tub and try to use a plunger, could that blow tub water back up into the AC unit? I was considering putting a stop valve in the middle of the condensate line that I could close in case of a tub backup emergency. Is this even required or complete overkill... OR.. or there any other issues that I could later face that I'm not even considering using this setup? Thanks in advance for any and all advice.