Elevating tub; bubble on level

[Pitterpat]

Remodeling my bathroom and I turned my tub 90 deg. Now the tub runs perpendicular to the joists, meaning where the tub is located the drain goes across the joists and would need to be cut (hacked up) to run the drain. I have come up with the bright idea (maybe not too bright) of elevating the tub so the drain is above the current floor and the vertical drain will just go straight down into the basement to be hooked up to the drain stack in the basement. I'm wondering how much the bubble should be on the level should be, a 1/4 bubble or a 1/2 bubble or less.

Right now I have the rear of the tub sitting on three 2 x 8's and the front of the tub on two 2 x 8's plus 3/4" of plywood. Also, this is a left hand tub that I'm using as a right hand tub. Why because I want the faucet to be toward the front not the back of the area.

 

[Terry]

The top edge of the tub should be level. The slope that drains the tub is built in.
I have used tubs that were raised, and nearly fallen when stepping out of the tub. If you do raise the tub, make sure you raise the flooring where you would come and go.
Plumbing pipes need 1/4" per foot grade. The p-trap gets vented within 42" before entering the other plumbing.

 

[Sponsor]

 

[Pitterpat]

Thanks Terry. This is an old cast iron, there are 2 nubs / little legs that created the slope of the tub. The 2 nubs are of different lengths. It's also a very low tub, like 12" high.

I also forgot to mention I have never used this tub in the 4 years I have lived here and don't expect to in the future.

 

[Jadnashua]

Terry's comment is right on, and should be seriously kept in mind. Should someone try to exit the wet tub, stepping over the edge to a lower point by more than say the typical tub floor height to the room floor means putting your leg and foot at a significant angle, and with the wet, and maybe quite slippery surface from soap or conditioner, or really bad if anyone likes to use oil conditioners, VERY dangerous. A step on the outside of the tub at the 'typical' floor height would eliminate , or at least lessen that problem. Sometimes, it's better to box in the drain below the floor at the ceiling height underneath.

The rim, L-R, should be level and in-out.

 

[Pitterpat]

Tub is gone, it will be a shower only bathroom.