Installing New Kohler Bathtub, Vertical Pipe (Vent Stack?) in the Way

[Vci15]

My bathroom (house built in 2002) is on the top floor of the home (3 floors) and I was able to remove the existing bathtub and now I'm preparing to put in the Kohler Underscore 60x30 bathtub

Of course with my luck there seems to be a problem. There is a black pipe (vent stack?) that is going vertical into the ceiling but part of it is protruding into the space where the tub is supposed to go. The Kohler tub doesn't have that much room to spare on the side so it seems the black pipe is going to have to be rerouted somehow. The pipe extends 4" from the stud where the bathtub flange is going to be against. Below are the pics of the bathroom and Kohler tub. Anyone know what kind of options I have? What is this pipe for?

 

[Terry]

If this is the top floor of the home, then I would guess that it's a vent pipe. Maybe for the tub drain, or perhaps for plumbing below. Without knowing the plumbing layout, it would be a guess. The tub drain would have a vent somewhere, to prevent siphoning of the trap.
Options, If you have 2-1/4" to spare, maybe cut some of the stud out to fit the pipe in closer in the corner there. That stud is mainly to support backer board in the corner and there is none below the tub anyway.

 

[Sponsor]

 

[wwhitney]

Seems like that vent junction shouldn't be below the tub flood rim, as presumably one of those two vents is for the tub itself.

But given the number of studs in that side wall, that is presumably a structural post that you can't pass the vent through. Can you take a look or stick a camera into the subfloor cutout for the tub waste arm? Maybe you could lower the horizontal vent leg below the subfloor, and come up along side the vertical vent stack, joining the stack at least 6" above the tub flood rim.

Cheers, Wayne

 

[Jeff H Young]

outside wall with a window my guess judging by the insulation. But I wouldnt care? id just move the vent tight to the wall and do a little surgery to the stud in corner no worrys. that tub is going in ill make it fit!

 

[Vci15]

Seems like that vent junction shouldn't be below the tub flood rim, as presumably one of those two vents is for the tub itself.

But given the number of studs in that side wall, that is presumably a structural post that you can't pass the vent through. Can you take a look or stick a camera into the subfloor cutout for the tub waste arm? Maybe you could lower the horizontal vent leg below the subfloor, and come up along side the vertical vent stack, joining the stack at least 6" above the tub flood rim.

Cheers, Wayne

is this maybe what you mean? going from the top image to bottom image? And when you mention vent junction, you're referring to where I highlighted in yellow? Essentially I should keep that junction as is since it seems to be above the tub flood rim?

 

[wwhitney]

So, I misinterpreted the photos in your first post, I thought the fitting in the yellow box in your last photo would be a san-tee, with another vent coming up from below. Hence the comment about junction. Since it's just an elbow, ignore that comment.

That raises the question of just what is being vented by your vent. Is it for the tub itself, and if not, where is the tub vent? If it's for a fixture on the story below, the rules for how you can reroute it are less restrictive, and your last drawing would be fine (if that fits). If it's for the tub itself, then you aren't supposed to go horizontal until above the tub flood rim, which makes your options much more limited.

Cheers, Wayne

 

[Jeff H Young]

Push the vent against the wall make hole in floor a little bigger and notch the stud I'd put a new trap and waste and overflow and shower valve while your at it.

 

[Vci15]

So, I misinterpreted the photos in your first post, I thought the fitting in the yellow box in your last photo would be a san-tee, with another vent coming up from below. Hence the comment about junction. Since it's just an elbow, ignore that comment.

That raises the question of just what is being vented by your vent. Is it for the tub itself, and if not, where is the tub vent? If it's for a fixture on the story below, the rules for how you can reroute it are less restrictive, and your last drawing would be fine (if that fits). If it's for the tub itself, then you aren't supposed to go horizontal until above the tub flood rim, which makes your options much more limited.

Cheers, Wayne

Ok I cut a hole in middle of the subfloor to see if the drain goes to the vent and indeed it does. The drain makes a 90 turn to that pipe.

 

[Vci15]

Isn't the existing pipe already going horizontal well below the flood rim? What would be the difference with the proposal in my drawing

 

[Jeff H Young]

if the vent is against the studs tub still won't fit?

 

[Jeff H Young]

no its not horrizontal, its a 45 legal in our code

 

[wwhitney]

no its not horrizontal, its a 45 legal in our code

I think they may have used 60s to get it to fit below the tub deck, which is bending the rules a bit, but still better than 90s.

Cheers, Wayne

 

[wwhitney]

OK, so the problem solution, I think, is something like the crude drawing below.

The red stick figures represent the fittings and pipes. The p-trap u-bend is rolled back towards the vent wall as far as it will go without hitting the I-joist (which I understand runs parallel to the vent/valve wall). Then the p-trap elbow outlet is pointed perpendicular to the vent wall (as it is currently). Then a short section of pipe (not shown), an upright wye for the vent take off, then a LT90 (as currently), then a pipe segment connects to the existing trap arm (the current vent takeoff is capped or removed).

Assuming there is an I-joist between the trap and the vent wall, the tricky question is whether the p-trap is low enough so that you can get the vent through the I-joist via a hole in the web without hitting the I-joist top chord (which can not be modified). The wye can be rolled to 45 degrees off fully upright, which puts the vent at only 30 degrees from plumb, and means you could would use a 60 degree bend to turn up into the vent wall.

Also, I think that unless the tub waste, overflow and trap are accessible after installation, they are supposed to be glue joint fittings, rather than slip joint fittings So they should be replaced, which may be required anyway if your new tub has a slightly different drain and overflow placement compared to your old one.

Cheers, Wayne