Can I connect tub drain and overflow below joists instead of needing a standard rough?

[ARC]

Hi and thanks. 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 from the standard sideways "T" style?

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 (5") where the floor drain is. My basement is old and unfinished and all the plumbing runs below the joists so I have access. There is a 2"x4" subfloor brace but I can cut a gap in this if needed to get my a full 6.5" rough-in area, and if I turn the shoe 90˚ parallel to the 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 one buys with the downward santee for the floor drain and overflow, I'd like to turn the flor drain 90˚ and run it down to below the joist level. 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 gluing since I have 2"x6" for the wall cavity as mentioned, and room for the drain rough-in. Also, should I still add slip nuts to both lines because it's best practice and I have access from the basement? How does this plumbing plan sound and is it a legit substitute?

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.

 

[FishScreener]

I would be ok with that set up. Because it ties the overflow and drain together before the trap, and I would much rather see something like this, than find you had done a standard installation by destroying the strength of the joists by cutting into them.

But, check with your plumbing inspector to be sure they are ok with it.

 

[ARC]

I would be ok with that set up. Because it ties the overflow and drain together before the trap, and I would much rather see something like this, than find you had done a standard installation by destroying the strength of the joists by cutting into them.

But, check with your plumbing inspector to be sure they are ok with it.

Thanks for the bode of confidence FishScreener. Yeah, I don't want to cut the joists at all, but I know so many do. I couldn't find anything like this on the internet but this has to come up enough in first-floor baths with unfinished basements that make it possible.

It's essentially how the old clawfoot worked as the P-Trap was between the joists under the subfloor, but then the vent popped back up through the subfloor so that it could connect to the main vent branch that was in the wall cavity. I'm just lowering the P-Trap and making the vent in line with the wall cavity. You can see (bottom left) the water lines in and the hole that dropped to the P-Trap and then the vent still coming back up the floor to join the main branch.

 

[breplum]

The normal waste/overflow design is made to create a vent for the drain to allow free flow out the drain (and even then, we often see gurgling.
It might work, but gurgle a lot and certainly it is NOT to any code approval level.
The Tee (for the vent) on its back should be substituted with a combo on its back, but the combo you have picking up the w/overflow is best as a TEE, not a combo.

 

[ARC]

The normal waste/overflow design is made to create a vent for the drain to allow free flow out the drain (and even then, we often see gurgling.
It might work, but gurgle a lot and certainly it is NOT to any code approval level.
The Tee (for the vent) on its back should be substituted with a combo on its back, but the combo you have picking up the w/overflow is best as a TEE, not a combo.

I really appreciate you for the advice. So you're saying that the standard sideways "T" allows air from the overflow to allow the floor drain to breathe? Therefore it's not going to work like a wet-vent for the longer distance I have?

Thanks for the catch on the Tee on it's back. I knew better but still drew that in. I was thinking the vertical combo before the trap would just make cleaning easier, but you're saying a Tee is actually better. Out of curiosity so I know, why? Does this look better like to recommend?

And if I may ask one last thing, please. If it were then possible to angle the overflow with a couple of 1/16th bends or maybe one of those copper flex lines and some shielded couplings, is that better in your opinion?

Thanks so much.

 

[breplum]

Your last drawing does not resemble anything to do with plumbing that is designed to work and meet code in any way shape or form.
Yes, offsetting the overflow is done all the time, and certainly 1/16 bends are suitable. The smoother and less bends, the easier to snake from the overflow.
Copper flex would not be suitable because it is not drainage piping material...
A tee is the only fitting allowed when going from horizontal to vertical, but that only relates to vents and drainage. So in reality, the sweep of a combo in your case for the waste/overflow kinda does make sense.
I simply automatically corrected it thinking venting, but it is not hardly venting and such an abnormal installation that my correction doesn't make any sense.
I'd like to see you drop the tub drain straight down to pick up the w/o, then connect to a tee, and then you would have the normal-ish configuration. But, they don't make a drain fitting for a tub that goes straight down.
I do very much recommend you use sheilded no hub couplings to transition from 1.5" tubular from the waste/overflow parts to 1.5" plastic. They hold and seal perfectly without the risks of slip joint nuts/washers.
Be sure to come back when you put it all together to report on how much gurgling you get (if it drains at all, since there is no proper configuration on the drain.
If you have the room, consider a two inch p-trap to help everything flow.

 

[Zanne]

There are various configurations for tub drains:
1. Standard where there is a tub shoe that goes to an overflow
2. Direct drain where the drain is directly over the trap and the overflow is what elbows over to meet the tee below the drain
3. Back drain where the pipe is horizontal behind the overflow

and so forth.
You can do a modified Direct Drain & have the overflow pipe go long enough to pass under the joists.

Nice drawing by the way. The trap arm must be at least 2 pipe diameters long (so if you have 1-1/2" pipe it must be at least 3" long) and it must slope downward at 1/4" per foot. If it is not at least that long it is called a crown vent and will create a siphon (thanks to @frodo for that info).

My drawing/sketch isn't nearly as nice. I hope it makes sense. This is assuming it will line up.


You might need to reverse the direction of the trap/vent from my sketch and run it inside the wall behind the tub.
The trap arm must remain horizontal until it meets the vent. It can't go vertical before the vent. Now, you can have the vent come before it goes vertical though. I hope this is making sense.

 

[frodo]

.....

 

[ARC]

Thanks, both @frodo and @Zanne. I really appreciate the advice.

So should it be:
P-Trap under Overflow? (Drain feeds in horizontally) VERSION #1
OR
P-Trap under Drain's downturn? (Overflow feeds in horizontally) VERSION #2

I realize my side view drawing confused these two. Sorry about that.

 

[frodo]

click here

 

[Zanne]

I believe Keeney brand (could be mistaken) also sells a modular drain kit that can be configured in different ways. It can have direct drain, normal overflow type drain, or have the pipe continue out behind the overflow and then down for the trap. I like direct drain bc it seems like it would drain faster than having the tub shoe. Got a direct drain on friend's tub & it drains faster than tub shoe.

Thanks for the link, Frodo. I may end up using something like that for my tub setup when I switch to direct drain & repair & box the joist under my tub.

 

[ARC]

Thanks guys.

@frodo I'll do it that way for sure. Thanks for the clarification drawing.

@Zanne When you say "direct drain" would a schedule 40 female made for tub drains that lets the pipe go directly downward work better as in the Westbrass version on Amazon? Would there be a code issue? That would eliminate two of the 90˚ turns and I have the room.

This subject was difficult to decern in the codes. The only code I found in the UPC was 404.1 for overflows and I don't think the word "shoe" is anywhere in there.

Thanks

 

[frodo]

just stick a ftg clean out into the side of the shoe/ tee

 

[Zanne]

Arc, I believe you can. I was the one who asked the question about a tub drain going into it & was told it could be done that way. That was actually what I was planning to get. Question Link

It says it's for a tub without an overflow but it can also be used for a situation where you need to extend the pipe lower. I *think* you can still use a tub show gasket, but am not certain. I need to refresh my memory on how the tub drains go together- I've been focused more on shower drains as that is my next project.

There's also Keeney had a 71W overflow drain kit that is modular: https://www.amazon.com/Keeney-71W-Style-Triad-Chrome/dp/B000H5Q09I
Got one for my friend's tub but his fiance broke the plug for it (bc she couldn't figure out how to use it properly).

May just be easier to go with the Westbrass straight adapter and then have a straight run of 1-1/2" PVC pipe then have the sanitary tee. That's what I was thinking of doing for two of my bathroom projects at my house (other bathroom is getting a shower). I need to see if they have something like that adapter & an unboxed tub drain so I can see how they fit together at the hardware store next time I go.

Frodo is the expert though. @frodo, does the Westbrass fitting Arc linked look like it would work to put in a tub drain? Would it just thread into it?

I was told teflon tape should be used for that application. There is a related tub drain linked but sometimes the related stuff doesn't always match up.

Editing to add I think you could use the Westbrass adapter with something like this drain shoe. The rubber gasket goes on top of the tub instead of using plumber's putty (at least according to mfr answers). You would probably still want a thicker gasket under the tub like this one.
I'm not sure where or how a shank nut would fit in. I'm still researching.