Alcove Tub Drain/Rough-In Question I Can't Find An Answer To Concerning Joist & Wall Cavity.

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ARC

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Hi and thanks once again. I looked all over the internet but could not find my particular situation. I hope the answer will help others in the future too. Basically, can I change how/where the plumbing for a tub drain and overflow connect?

So my situation is I have a set of double joists mostly not directly under a 2"x6" wall that has the CI stack. The outermost joist is directly in the way of the downspout of the overflow and the joists run along the short end of the tub. I have room otherwise for the rough-in (6.5") where the floor drain is. My basement is old and unfinished and all the plumbing runs below the joists soi have access. There is a 2"x4" subfloor brace but I can cut a gap in this if needed to get my full 6.5" rough-in area, and if I turn the shoe 90˚ parallel to t joist before it heads downwards I for sure have enough room.

My question is can I connect the tub drain and the overflow separately to the 2" mainline that connects to the CI stack? Instead of doing the standard sideways "T" assembly with a santee for the floor drain and overflow, I'd like to run the floor drain down to below the joist level. I understand that the tub shoe is horizontal but I believe have room between the joists in the rough-in to then make a 90˚ turn straight down. I'd then run the overflow into the wall cavity which is 2"x 6". So the overflow would probably have a couple of 45˚s to run it over to the wall cavity, and then down. Then when they both are below the joists they will connect into the mainline going into the CI stack either separately or together with a combo. I should have enough room for the overflow to do the fitting and glueing since I have 2"x6" for the wall cavity as mentioned, and room for the drain rough-in. I'll still use slip nuts for both. How does this sound?

I don't see why this should be an issue, but I am here to ask the hive mind what they think I am not considering. I don't want to cut into the joists, or furr out the wall if I can avoid this, and I like this tub which doesn't have an above ground rough-in option. I will be removing the stub in the picture. I can't find this situation anywhere on the internet where someone did this so what do you all think? Thanks.
 

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Reach4

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Drainage from both paths must pass through a vented trap.

They also don't want slip joints that don't stay accessible.
 
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ARC

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Derp. I totally forgot to draw the P-trap! I planned on one, but thanks for the catch. I also realized I should have put the slip-nut closer to the tub but I already posted. I think this new drawing is more accurate. How does this look now? My main question is whether the idea is ok to do such an idea. What do you think?

Reach4: What do you mean slip nuts need to "stay accessible?" Would one in the cavity be a bad idea or is it better below the subfloor? What if I could still get to it through the bottom plate?
 

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Terry

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Your drawing does not show a proper trap with proper venting to prevent siphoning of the trap, allowing all kinds of sewer gas and fumes into the home.

dwv_b2.jpg
 

Reach4

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Reach4: What do you mean slip nuts need to "stay accessible?" Would one in the cavity be a bad idea or is it better below the subfloor? What if I could still get to it through the bottom plate?
I don't know the fine points. They normally want glued joints. If you feel you want rotational adjustment freedom during the work, you could use shielded couplings.

If there would be access to the "cavity" via an access panel after install, slip joint might be allowed. Not sure.

Really nice clear sketches that you drew.

The vent after the trap has to be before the pipe turns down. There must be at least 1.5x2=3 inches of horizontal and then a vent.

I don't know how far the path to the trap is allowed to be.
 

ARC

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Sorry. I think my poor attempt of drawing these types of things is the issue. The vent and Stack were above the tub, but of course wasn't obvious to others.

Maybe this drawing shows it better. This would be looking at the short side of the tub opposite the overflow and towards the 2x6 wall cavity with the CI stack.
 

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