Too many Elbows?--Location of Wye on "Main Stack"

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Amicrazy

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Hello all, long time lurker, first time user/poster, I appreciate all of the posts I've been able to read so far as they have helped me out with numerous other smaller projects. This one is a little bigger, and leaves me with some questions.

I'm replacing a cast main stack that was rotted out at the bottom and wanting to plumb a bathroom on the second story, and add a half bath on the main level. Attached is a mockup of my plan.

Screenshot_20221023-003012_Concepts.jpg



Green is Venting, any black lines coming off at a 45 degree angle indicate a wye fitting (with the exception of the bottom most 45 degree offset) All is plumbed in 3 inch with the exception of the Lav's, Tub and vents which are 2"

My first question is, can the main vent/stack take make that horizontal (with proper slope) or does a "main stack" always have to be vertical.

Not specific to this design, but I guess I'm a little curious/confused as to the purpose of the main "vent" if fixtures are vented by other means, is the "main stack's" primary purpose to move waste down from upper levels, or is the vent at the "end/top of the line" so to speak necessary.

Which brings me to my next question. Do I need the vent on the far left, or can the toilet and tub be vented through the Lav. If the vent is needed, should it be 3" or can it be 2"?

I tried my best to depict it in my plan sketch, but the position of the Lav on the second story, is "downstream" of the Wye, with some elbows I was able to come up with a solution that I think would work and meet code.

Which brings me to my final question of the night, would this be acceptable as the waste would be running "backwards" to the wye and would have to make a near 180 degree turn, is there a limit on how many elbows I can use to make this work?

Screenshot_20221023-004357_Gallery.jpg



Thanks in advance for any input!
 

wwhitney

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Your diagram is non-standard in its rendering of 3 dimensions on a page, but I think I follow it.

0) At the upper left, you have a horizontal dry vent below the fixture flood rim, that is not allowed and needs to be eliminated. You could reroute the tub drain so that it just goes the direction out of the page, then turns right to hit that vent and the left-right horizontal branch.

1) A stack by definition is vertical, but there's no requirement to have a stack that goes all the way from the basement through the roof. You can have a horizontal branch drain at the top of the stack as you show.

2) Yes, as drawn you need the vent on the left, as it is the dry vent for the tub and the wet vent for the WC. The lav can't wet vent the tub and WC when the lav is the 3rd fixture on the branch.

If you reroute the lav drain to join the horizontal branch between the tub and the WC, then it might be able to wet vent both the tub and the WC. It would need to hit the tub drain sufficiently close to the tub trap.

3) I don't follow the question or what your picture is supposed to be showing. Also, I don't take your diagram to be showing specific fittings at the connections, so there are still details not shown on which fittings are required.

Cheers, Wayne
 

Amicrazy

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Thanks for the feedback Wayne!

Unfortunately I don't think i'd be able to move the lav between the W/C and tub.

That make a lot of sense, but also a brings a few follow-up questions.

You could reroute the tub drain so that it just goes the direction out of the page, then turns right to hit that vent and the left-right horizontal branch.
I think I have an idea of where you are going with this thought...but maybe I am misunderstanding.

Instead of coming off the straight end of the wye, but rather attached at the 45 degree outlet, would the vent then be considered vertical and allowed in this instance? Could the tub could connect to the straight end of the wye?

OR... would I need a San-tee to connect the vertical vent, trap arm, and 2-45's to make the bend to connect to the end of the left-right branch.

Screenshot_20221023-153122_Gallery.jpg


Hopefully this picture is a bit clearer without the markup. The wye is installed in the correct orientation with waste flowing from the top of the photo to the bottom.

Coming off the wye is 2 street 45's and another 45 bend in the middle, before attaching with another 45 that will go vertical to the san-tee.

The direction of waste flowing from the final 45/san-tee to the wye is the opposite, from the bottom of the photo to the top, where it would reverse and (hopefully) flow the other direction.

Any feedback or additional wisdom is appreciated.

Thanks again!
 

wwhitney

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Instead of coming off the straight end of the wye, but rather attached at the 45 degree outlet, would the vent then be considered vertical and allowed in this instance? Could the tub could connect to the straight end of the wye?
If the barrel of the wye is horizontal, and the tub drain is coming in the straight inlet, then the side inlet of the wye needs to be upright (rotated 90 degrees around the barrel from a "flat" position) for a dry vent to connect to the side inlet.

Hopefully this picture is a bit clearer without the markup. The wye is installed in the correct orientation with waste flowing from the top of the photo to the bottom.
If the photo is generally looking downward, so that the hub in the foreground is level in both directions (i.e. a pipe in it would be plumb), and the pipe at the bottom that the barrel of the wye is attached to is horizontal, then that configuration is fine for a drain. I see how in plan it sort of corkscrews 180 degrees, but everything is vertical (in the plumbing code, that includes up to 45 degrees off plumb), so there's no issue.

Cheers, Wayne
 
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