Giantsean
Member
The vent comes off at the same level as the trap arm, not below.
When it's vented below, it can still siphon the trap. That's why your plumbing inspector said it was too low.
Apologies I think (I hope) you got me wrong. I still plan to scrap the fully intend to rework it as per the advice here (assuming it's still same as the pic below). The vent will go up the wall behind the bay that the tub drain is in.
The only thing I wanted to confirm is whether I could tie in the trap somehow to the existing 2" drain somewhere before it drops below the ceiling, as it's already hooked up down below and would be much easier to cut inside the floor. That's all.
If you're saying I can't do that under any circumstance until it goes through the sheetrock into the room downstairs, then it's a moot point and I will have to find a way to raise the entire tub drain line