Help with redesigning stack

[Mosho]

I would like to move an exposed part of my main stack into a wall. Pretty simple I think:

Serves a single bathroom, toilet from the top 3'' and tub/shower and vanity sink from the 1.5''.

My questions:

1. Is a 1.5x3x3 wye installed vertically the right fitting at the top?
2. Would it be better to go as steep as possible as soon as possible (e.g. a 45 under the beam then connect to the vertical stack) or go horizontal first and connect to the vertical 3'' on the right right below the beam?

Thanks!

 

[wwhitney]

One comment: any rubber couplings used above ground should be the metal shielded variety. The unshielded variety is only for use below ground.

So you've got 3" cast iron in the leftmost joist bay, and 1.5" (cast iron?) in the joist bay next to it (above the red X)? And you're going to have a framed 2x6 wall that is directly in front of the I-beam? And you want to turn both drains down into the wall, and connect them, and end up at the bottom right?

Then I'd say turn the 3" line downward at a 45 to the right using a quarter bend. Then turn the 1.5" straight down with a quarter bend. Join them with a 3x3x1.5 wye with the 3" barrel at a 45, the 1.5" inlet pointed straight up. Continue with the 3" line at a 45 until over the bottom of the stack, and use a 3" 45 to turn downward.

Cheers, Wayne

 

[Sponsor]

 

[Mosho]

One comment: any rubber couplings used above ground should be the metal shielded variety. The unshielded variety is only for use below ground.

So you've got 3" cast iron in the leftmost joist bay, and 1.5" (cast iron?) in the joist bay next to it (above the red X)? And you're going to have a framed 2x6 wall that is directly in front of the I-beam? And you want to turn both drains down into the wall, and connect them, and end up at the bottom right?

Then I'd say turn the 3" line downward at a 45 to the right using a quarter bend. Then turn the 1.5" straight down with a quarter bend. Join them with a 3x3x1.5 wye with the 3" barrel at a 45, the 1.5" inlet pointed straight up. Continue with the 3" line at a 45 until over the bottom of the stack, and use a 3" 45 to turn downward.

Cheers, Wayne

Roger on the rubber coupling, I'll replace that.

The 1.5'' is all ABS now after I replaced it but was cast iron. I want to move it into the wall as well (the green lines top left) so that it is going into the back of the 3'' going down from upstairs. So I can't really get it in front of the 3'' to accommodate the 45 wye unless I make the wall significantly wider than a 2x4.

The wall under the beam is actually 8'' wide same as the beam, so plenty of space there. But the wall perpendicular will be just 2x4. Makes sense with two 45s to me, but I would also need a 90 between the perpendicular walls, right?

 

[wwhitney]

The wall under the beam is actually 8'' wide same as the beam, so plenty of space there. But the wall perpendicular will be just 2x4.

So now I'm a little confused: the wall parallel to the beam will just be under the beam. There will be a 2x4 wall perpendicular to the beam, so any pipe in the joist bay above that 2x4 wall can dive into the wall to pass under the beam and turn down into the wall under the beam. But you have pipes in two different joist bays, so one perpendicular 2x4 all can't do that for both joist bays. Are you planning a soffit on one side of the 2x4 wall?

My first answer was based on the simpler case where the wall parallel to the beam is not directly under the beam.

Cheers, Wayne

 

[Mosho]

So now I'm a little confused: the wall parallel to the beam will just be under the beam. There will be a 2x4 wall perpendicular to the beam, so any pipe in the joist bay above that 2x4 wall can dive into the wall to pass under the beam and turn down into the wall under the beam. But you have pipes in two different joist bays, so one perpendicular 2x4 all can't do that for both joist bays. Are you planning a soffit on one side of the 2x4 wall?

My first answer was based on the simpler case where the wall parallel to the beam is not directly under the beam.

Cheers, Wayne

Yeah, it's directly under the beam. The double 90 currently in the 3'' gets it from the joist bay under the beam. I'm going to move the 1.5'' into the same joist bay as the cast iron pipe and the 3'' though, so they will be in the same 2x4 wall.

 

[wwhitney]

Yeah, it's directly under the beam. The double 90 currently in the 3'' gets it from the joist bay under the beam. I'm going to move the 1.5'' into the same joist bay as the cast iron pipe and the 3'' though, so they will be in the same 2x4 wall.

So the 2x4 wall perpendicular to the beam is going to be under the 3" drain (which looks to be very low in the joist bay). You're going to drill the double joist so that the 1.5" drain can move over into the same joist bay and also drop into the wall. Is that correct? What's the vertical difference between the center lines of the 1.5" drain and 3" drains as they are running parallel to the joists approaching the beam?

If that's correct, then one simple option would be to combine the 1.5" and 3" with a vertical wye with 3" barrel at a 45, similar to my first answer, but within the 2x4 wall. The 3" would turn from horizontal with a 45, and the 1.5" would use a horizontal LT90 to go through the double joist, and a quarter bend to turn down into the 2x4 wall. Then they join with the wye, and the combined pipe continues to the intersection of the 2x4 wall and the wall under the beam. If falling at a 45, and you way to turn the corner in plan, from the 2x4 wall to the wall under the beam, you need a 60 degree bend.

Cheers, Wayne

 

[wwhitney]

Another option, if you're willing to have a small soffit against the beam:

Run the 3" drain in the joist bay and just before the beam, turn it down into the 2x4 wall with a quarter bend. The 1-1/2" drain stays in its current joist bay, and again just before the beam, it turns down into the soffit with a quarter bend rolled 45 towards the 2x4 wall, and a 45 to go horizontal (2%), as high as possible under the joist. Then it goes through the soffit to hit the 3" on the vertical; a 3x3x1.5 combo would be good, but a 3x3x1.5 san-tee is allowed and would make for a shorter soffit.

Now the combined 3" drain wraps around the corner with a 45, then a 60, then a 45 to turn down vertical over the existing stack location.

Note that with 3" fittings in your 2x4 wall, you should plan to fir out the wall at least 1/2".

Cheers, Wayne

 

[Mosho]

So the 2x4 wall perpendicular to the beam is going to be under the 3" drain (which looks to be very low in the joist bay). You're going to drill the double joist so that the 1.5" drain can move over into the same joist bay and also drop into the wall. Is that correct? What's the vertical difference between the center lines of the 1.5" drain and 3" drains as they are running parallel to the joists approaching the beam?

If that's correct, then one simple option would be to combine the 1.5" and 3" with a vertical wye with 3" barrel at a 45, similar to my first answer, but within the 2x4 wall. The 3" would turn from horizontal with a 45, and the 1.5" would use a horizontal LT90 to go through the double joist, and a quarter bend to turn down into the 2x4 wall. Then they join with the wye, and the combined pipe continues to the intersection of the 2x4 wall and the wall under the beam. If falling at a 45, and you way to turn the corner in plan, from the 2x4 wall to the wall under the beam, you need a 60 degree bend.

Cheers, Wayne

The 1.5'' is above the bottom of the joists so there's a big different vertically. It would turn down as you said to connect to the wye. I'm not sure how you mean the wye would be oriented, do you mean that it's completely vertical so that the 1.5'' goes into it at a 45, or is the wye itself at a 45 so that the 1.5'' can connect to it horizontally?

And why do I need a 60 degree bend? If the 3'' goes into the wall under the beam at a 45 towards the floor, wouldn't I need a 90 to make it parallel with the beam (but still going down at a 45), then a 45 to connect to the pipe out of the slab?

 

[wwhitney]

The 1.5'' is above the bottom of the joists so there's a big different vertically. It would turn down as you said to connect to the wye. I'm not sure how you mean the wye would be oriented, do you mean that it's completely vertical so that the 1.5'' goes into it at a 45, or is the wye itself at a 45 so that the 1.5'' can connect to it horizontally?

My proposal had the 1.5" connecting to the wye from above, while the 3" is falling at a 45 from left to the right. But there are lots of options.

And why do I need a 60 degree bend? If the 3'' goes into the wall under the beam at a 45 towards the floor, wouldn't I need a 90 to make it parallel with the beam (but still going down at a 45), then a 45 to connect to the pipe out of the slab?

Nope. The angle between "downwards from left to right at a 45 in the 2x4 wall" and "downwards from left to right at a 45 in the beam wall", where the two walls are at 90 degrees to each other, is 60 degrees.

If you think about it, with a LT90, you could turn from "horizontal from left to right in the 2x4 wall" to "downwards from left to right at a 45 in the beam wall". That would be done by putting the LT90 horizontal, and then dropping the right end enough so you're 45 degrees below horizontal in the beam wall. So for the case in the earlier paragraph, it's going to be a smaller angle, and it turns out to be 60 degrees. [In vector math, (0, 0.707, 0.707) dot (0.707, 0, 0.707) = 1/2 = cos(60).]

Cheers, Wayne

 

[Mosho]

My proposal had the 1.5" connecting to the wye from above, while the 3" is falling at a 45 from left to the right. But there are lots of options.



Nope. The angle between "downwards from left to right at a 45 in the 2x4 wall" and "downwards from left to right at a 45 in the beam wall", where the two walls are at 90 degrees to each other, is 60 degrees.

If you think about it, with a LT90, you could turn from "horizontal from left to right in the 2x4 wall" to "downwards from left to right at a 45 in the beam wall". That would be done by putting the LT90 horizontal, and then dropping the right end enough so you're 45 degrees below horizontal in the beam wall. So for the case in the earlier paragraph, it's going to be a smaller angle, and it turns out to be 60 degrees. [In vector math, (0, 0.707, 0.707) dot (0.707, 0, 0.707) = 1/2 = cos(60).]

Cheers, Wayne

Had to go downstairs and try it out for myself pretty cool. Sounds good though, I'll go look for the parts I need, thanks!

 

[Mosho]

@wwhitney Hi! Would it matter if I did the 45 -> 60 -> 45 part at the bottom instead of the top? for drainage but also noise etc.

edit: also, would it be beneficial to add a cleanout anywhere? there's one at the bottom of the stack going into the slab.

 

[wwhitney]

1) Sure you could put it lower if you like. That would change how the 1.5" connects with the 3" perhaps and end up introducing an a net extra 90 (horizontal to vertical) in the 3" line, but that's fine.

I don't see the advantage, though. If you're concerned about noise, do the work in no hub cast iron.

2) Definitely need to preserve the existing cleanout, you could move it if you want, but I don't think there's any need for two cleanouts.

Cheers, Wayne

 

[Mosho]

@wwhitney made good progress, but not sure about this section:

The 90 top left is connected to the pipe coming out of the hole in the joist at whatever angle is needed to connect to the 22.5. Should I instead have the 90 go horizontally and use two 22.5s? Something else entirely? I'd remove that 2x4 and just go horizontal and a 45 but the cast iron is in the way.

 

[wwhitney]

How does this latest photo relate to your earlier photos spatially? What's the cast iron carrying and what's the 1.5" (?) ABS carrying? And how about a photo that is looking straight up from underneath the joist bay with the cast iron and the 2x4 bottom of bay cross block?

Cheers, Wayne

 

[Mosho]

How does this latest photo relate to your earlier photos spatially? What's the cast iron carrying and what's the 1.5" (?) ABS carrying? And how about a photo that is looking straight up from underneath the joist bay with the cast iron and the 2x4 bottom of bay cross block?

Cheers, Wayne

It's the top left part of the first picture, the 4'' cast iron is right to the right of the pipe with the 22.5.

Cast iron is from the toilet and the 1.5'' is the shower and sink.

Here it is from below:

 

[wwhitney]

So is replacing the 4" cast iron an option? I assume that the closet flange is right above the 2x4 bottom of bay cross block. If replacing the cast iron is possible, you could join the 1.5" and the WC drain in the joist bay, and the lavatory would be wet venting the WC.

If replacing the cast iron isn't an option, and you just want to get everything into the "2x4" wall that we were discussing earlier (except with 4" cast iron in it it won't be a 2x4 wall, it will have to be bigger), then the solution in your picture is elegant, in that it just uses a LT90 rolled down 22.5, a 22.5, and a vertical wye. The only down side is that the 1.5" line at a downward 22.5 degree angle is going to need a long slot in the top plate. But if it's a 2x6 non-bearing wall, cutting a 2" slot in the top plate is no big deal, that leaves you with 1.75" of wood on either side of the slot.

If your ABS is all dry fit, you understand that for the final glue up you will need to slightly cut longer pipe segments?

Cheers, Wayne

 

[Mosho]

So is replacing the 4" cast iron an option? I assume that the closet flange is right above the 2x4 bottom of bay cross block. If replacing the cast iron is possible, you could join the 1.5" and the WC drain in the joist bay, and the lavatory would be wet venting the WC.

If replacing the cast iron isn't an option, and you just want to get everything into the "2x4" wall that we were discussing earlier (except with 4" cast iron in it it won't be a 2x4 wall, it will have to be bigger), then the solution in your picture is elegant, in that it just uses a LT90 rolled down 22.5, a 22.5, and a vertical wye. The only down side is that the 1.5" line at a downward 22.5 degree angle is going to need a long slot in the top plate. But if it's a 2x6 non-bearing wall, cutting a 2" slot in the top plate is no big deal, that leaves you with 1.75" of wood on either side of the slot.

If your ABS is all dry fit, you understand that for the final glue up you will need to slightly cut longer pipe segments?

Cheers, Wayne

I would very much like not to replace the cast iron, yeah. I might make the wall a bit thicker if I don't think I can accommodate the width with finishes.

That's a very good point about cutting things slightly longer... I did do that but I was off in one 3'' pipe somehow and it's not very deep into the hub... Everything is cemented and there are no leaks but is there a way to fix that?

 

[wwhitney]

I was off in one 3'' pipe somehow and it's not very deep into the hub... Everything is cemented and there are no leaks but is there a way to fix that?

If it's all cemented, the only fix is cutting it out and redoing it. A 3" hub is 1.5" deep, if you have 1.25" of engagement that's fine; 1" is marginal; 3/4" might be a redo; 1/2" I would definitely redo. Others might be more or less stringent.

Cheers, Wayne