In Australia and many places in Europe this second floor drain is a most and required by their countries "Plumbing Code". I think these second drains should always be used with a channel drain / curbless shower installation. I reviewed this subject with my local plumbing inspector and he informed me that a plumbing system designed and built properly to code does not need the second drain to pass inspection. "But is it a good idea?" I think so. David's concealed drain the most applying concept to me so far! - buried under the vanities kick or deep behind a free standing or floating piece (a second channel drain up tight to the baseboard?). Some of the options for designer drains available through California Faucets are amazing - all the top bathroom shops carry them. This second drain and fail safe would offer up better protection if a clog caused by blocked hair, wash cloth, foot, toys ("Little People & their stuff") went unnoticed in the Peak of Play Time. There are issues with priming this second drain line and many was of doing just that - have a ticketed plumber help you with the lay out to be approved by city hall. My kids bathroom floor is heated and I slopped this floor a hair so dripping water would not sit up against the tub base and baseboards (Wood). If a drip or slow leak happen I hope this will bring it out to the center of the room for us to notice and repair. I designed my daughters vanity piece to have 6 drawers, 2 sinks and an open back to work on and service the plumbing connections. In my en-suite I will rip up the floor and follow David's advice on a concealed back up drain. This second drain will cause my curbless shower to have compound angles so I'm thinking we should look at a 4"x4" tile or smaller for the floor. More work.... Safer.... Nice.... Perfect.

You can get integrated 2-sided tubs or deck mount. I would absolutely NOT do freestanding in such a case. It's just not possible for any kind of cleaning. Drop in tub plus wall flange works fine for this installation though if you can't find 2 wall. My plan allows for a deck mounted filler in a pony wall type scenario at the end of the bathtub, but there are other possibilities. Those measurements are to studs, not to the opposite drywall, aren't they? 91 and x/4 (can't read x) minus 2 sheets of drywall gets to 90 and x/4. Unless she is measuring really weird!!!! You can mount a deck faucet on the tub itself if you get the right tub. It works just fine. You can also mount it on the end of the tub or get one that is wall-mounted. You can have a wall tub spout just fine with a 2-wall tub.

Thanks for all the comments. I ended up getting a nice 13 amp grinder with a concrete grinding wheel. Since about 1/5th of the floor is the hump I opted for the grinding. So far I have taken about 1/4" down. As far as the "pros" and "experts"... this concrete was done by the "pros". The rough framing which I've had to fix in multiple spots was also done by "pros". The HVAC runs that I have had to re-adjust so that sheet rock will fit on the walls was done by "experts". The upstairs tub, which had the overflow leak all over the downstairs ceiling, was also done by an "expert". All those things are what makes me a DIYer. Thanks again for all the perspectives.

LOL, I knew about soldered copper, but had never heard "sweat". I learned something new! Thanks. One plumber did not know they were hard copper and can't be bent. Not good... So, the connections/fittings will be soldered if copper, or they will be PEX. They will be under the concrete when lengthened. Both plumbers said that was not to code, but they didn't seem to care since no one will inspect inside the concrete. I just want the job done correctly, but it seems like it will not be to code. Thanks for your help. Now, I will know a little more about what the plumber should do. I have had 3 or 4 plumbers come here to do the work, then they change their minds I guess. They say they will call me, but I don't hear from them, and they don't respond to my calls. I found another plumber through my electrician, and he is supposed to come Tuesday. I can't believe this bathroom has been gutted since April, and nothing has been done yet. Southeastern Oklahoma used to have cold winters, but we rarely get past freezing now. Last ice storm was 2007.