Double fixture + sanitary tee stack?

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RxC

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Hello all!
Renovating to add a double vanity. This will be my first solo run after doing work with my dad.

Existing setup has another sink back to back in the master bath. Plan is to merge and reroute the two left vents further left to make room for an added drain to the left.

Current drain is in roughly the right position. Going to replace the section of copper with PVC but questioning my options. Do I stack a sanitary tee under a double fixture, run both drains for the double vanity to the left with a stack of sanitary tees or something else?

Since the vent will be sweeping left am I better to vent off the new left drain or is that overkill?

Happy for any advise as I keep learning.
IMG_6541.jpeg
IMG_6527.jpeg
 

RxC

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Hello all!
Renovating to add a double vanity. This will be my first solo run after doing work with my dad.

Existing setup has another sink back to back in the master bath. Plan is to merge and reroute the two left vents further left to make room for an added drain to the left.

Current drain is in roughly the right position. Going to replace the section of copper with PVC but questioning my options. Do I stack a sanitary tee under a double fixture, run both drains for the double vanity to the left with a stack of sanitary tees or something else?

Since the vent will be sweeping left am I better to vent off the new left drain or is that overkill?

Happy for any advise as I keep learning.
View attachment 103161View attachment 103160
For clarification pvc vent is coming from the first floor laundry discharge and center copper vent is from a bathroom. Work shown is existing from the prior owners.

New drain and supply will be ~58” from current drain and land where the pipes turn vertical to feed the master shower on the other side.
 

RxC

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This was pending approval for a moment. Bumping to get some eyes on it. Can draw I top of the image my planned path if it is unclear. This one has me scratching my head on how to approach best.
 

wwhitney

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Assuming you are replacing the double wye copper fitting, use a double fixture fitting to replace it. If you would prefer not to replace it, you need to check the elevation of the trap weirs relative to the inside crotch of the double wye (where the the vent starts) to see if it's OK to continue to use, or needs replacement anyway. I can explain further if necessary.

Your main problem is going to be crossing the new horizontal drain line over the two vents to reach the existing drain line. Is that drain line 1-1/2" or 2"? Do you have enough depth in the wall to cross over? If not, you either have to take the new drain downward and deal with it on the floor below, or maybe cross over outside the wall and conceal it within a vanity.

Cheers, Wayne
 

RxC

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Hi Wayne- Thanks for replying. I plan to replace the current double wye with my new PVC setup. This is what I am thinking with the sections marked black removed and routed left and around following the green path. Everything is 1.5” in the photo. Just right of the upper vent intersection it transitions to 2”. The main stack is about another 2ft to the right.

I have a double fixture to install to replace the current drain and that for the master bathroom sink on the other side of the wall. Drain height currently is 18.5in to center. Am I better to run a sanitary tee from just below the double fixture (yellow dot) for the new drain? Or do I scrap the double fixture and instead replace with a sanitary tee feeding the master bath sink and another sanitary tee at the yellow dot to handle the existing drain relocated just left to the red dot on the same leg as the new drain far left? Advantage in my mind is the drains for the new double vanity are on the same run and maybe more similar resulting height minus slope.

For either approach, should I tie back into the vent near the new left drain since over 30”?
IMG_6556.jpeg


This would be the double fixture setup and orientation. Figuring 1/4” per foot the drains will be 5” different in height. The alternative would put the existing drain about where the water feed is with the new drain further left on the same line would put them about 1” different.

IMG_6558.jpeg
 
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wwhitney

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Preliminary comment: since you mention a main stack to the right, and a bathroom on the wall behind, best answers would require you to post a diagram of all the DWV in both bathrooms and the main stack. My answers previously and below are somewhat piecemeal without that info, so there may be an oversight. [Conversely, if that left hand vent is a dry vent for a single fixture in the bathroom behind, it might be possible to turn that into a wet vent and use it for drainage from the new lav, which would save you having to reroute the vents as you propose.]

As for rerouting those vents as shown, are they both from fixtures on the floor below? If either one is a fixture on this floor, (WC or shower or tub or whatever, in either this bathroom or the bathroom behind), then you can't have it turn horizontal below the fixture flood rim. [On which basis, since the vent comes up from the floor below, there should be a drain running through the floor system next to or under the wall, so the vent can be taken off plumb or at most 45 degrees from plumb, which still counts as vertical. It's also possible that there is an improper horizontal vent below the floor.]

[On the other hand, if that left hand vent is a dry vent for a single fixture in the bathroom behind, it might be possible to turn that into a wet vent and use it for drainage from the new lav, which would save you having to reroute the vents as you propose. You could even leave the copper double wye as is, assuming you confirm the trap weir rule is complied with despite the wye.]

But if they are both from the floor below, your green rerouting works and keeps you from having to cross the new trap arm over a vent within the wall. [Upon reflection, this doesn't seem too likely, as more typically they would be combined in the story below so that only a single vent runs up between floors.]

As to the drain side of things, you want to put 3 lavs into a single 1-1/2" drain. That is allowed on a horizontal branch, but oddly not allowed on a single floor for a stack. (IPC Table 710.10(2)) So does the 1-1/2" drain basically turn immediately to the right to hit your main stack, or does it proceed downward for at least one story? The latter would make it a stack, which would mean you are not supposed to put in 3 lavs all on the same story, and as an alternative you are supposed to tie into the main stack.


Assuming you can put 3 lavs into that 1-1/2" copper drain coming up from the floor, since it is 1-1/2" in diameter, you can't use a double fixture fitting, as they all have 2" outlets to my knowledge. A simple arrangement would be 3 separate san-tees, located horizontally and vertically where you want, one for each lav, each with a vent riser to the upper horizontal vent in your proposed rerouting. The fact that two of them would be so close together would complicate combining their drains, but it would be doable. Other arrangements are possible, e.g. one dry vented lav wet venting lav one or two of the lavs, but with that proposed horizontal vent so conveniently located, dry venting each one seem best.

So that's not quite a complete suggestion, particularly on the how the three lav drains would tie together. I'll wait for some more info before commenting further.

Cheers, Wayne
 
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RxC

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Hi Wayne,

I am definitely feeling my novice status while trying to digest the great information you are sharing. Threw the below floorplan together for the two bathrooms sharing this wet wall. Not sure where all the DWV runs thanks to the joys of a quad-level home.

On the double-fixture it is 2" natively on the downward side, would it be ill-advised to reduce to 1-1/2" before connecting back to the copper with a proflex collar?


Bath.jpg
 
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