I have back to back bathrooms. The current lavatories drain to a wye then to the vent further down the wall (behind the toilets). I want to raise the P-trap for one of the lavatories (putting in a vanity with an open middle and trying to hide as much of the plumbing as possible). I presume I cannot connect the higher p-trap into the existing drain pipe as that would seemingly make it an s-trap (which I think I read were not allowed in the US anymore). So it would seem I have to take down the drywall, run a separate drain to the vent for the higher p-trap. That is oh-so much work for about 8 inches of height... any other options? (BTW is there an minimum distance that the bottom of the p-trap has to be below the bottom of the lavatory? I know it has to hold enough water to prevent the gas from coming up, and there needs to be some working space for the coupler...