Back to back toilets in horizontal main

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tmcnutt18

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I have back to back bathrooms that are a mirrored image of each other. The main line will start beneath the bathrooms and be a horizontal line that I would like to keep in the floor joist space. I'm trying to figure out how to plumb the toilets. They are back to back. I'm thinking the first toilet would be a 4 x 3 closet bend into the main, then a 3 x 3 x 1.5 Wye with a 1.5" street 45 for the vent up the wall that divides the bathrooms. Should I use a 3 x 3 x 3 Wye with a street 45 to pick up the next toilet? How can I connect 4" toilet line? What about vent for this toilet? Could I do another 3 x 3 x 1.5 at a slight angle from horizontal over to the next joist space and then back to wall between bathrooms?

Thanks,
Tom
 

Terry

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One 2" vent would vent both toilets. I would use wye fittings. You only need 3" and they make 4x3 closet flanges. Toilets typically have a 2" trapway dropping into a 3" line.

 
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tmcnutt18

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Terry,

Thanks for replying. Can the vent be between toilets so I can run vent up dividing wall? See attached drawing that lists fittings. Let me know if this would work. Do you recommend Wye and street 45 instead of long sweeping one piece wye?

Thanks,
Tom
 

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WorthFlorida

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Yes, the vent would go straight up on the center. Reduce it down to 2".

Screen Shot 2019-12-05 at 1.44.40 PM.jpg
 

tmcnutt18

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I don't think I have enough room to use a double Wye and keep main line in joist space.
 

Reach4

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See back to back bathrooms on the lower left of https://terrylove.com/forums/index.php?attachments/upc_wet_venting_bathrooms-jpg.34573/

That would satisfy UPC. Kentucky State Plumbing Code is based on an IPC precursor, so KY code would probably be more permissive. Current IPC is more restrictive than UPC in one area that I know of: they would want the pipe below the lavatory to be raised from 1.5 to 2 inch and the wet-vented section carrying the shower water to bump to 3 inch.

I suspect your dry vent diagram is fine, except that I think that instead of a tee, that would be a 3x3x2 wye+45 or combo. I think that is to minimize getting solids into the vent.
 

Reach4

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Are these double wye/ 1/8 bend fittings readily available? I am having trouble locating these at the box stores, only finding double fixture fittings which look slightly different (to my untrained eye at least).
You want ABS I presume.
 

Reach4

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I am not finding that so far. You can use a double wye
black-abs-fittings-c5834hd3-64_145.jpg
and two street 45s.

A double fixture fitting would be nearly as good, and is easier to find.
plastic-abs-fittings-c5835bhd3-64_145.jpg
 

Allison

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Are there online suppliers that carry the double wye/ 1/8 fitting? Everything I've found looks just like like a double fixture fitting. I was under the (maybe wrong) impression that the wye+45 and double fixture fitting wouldn't pass UPC for back to back toilets.
 

Reach4

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All that carry much in ABS would have a double wye and two street 45s. That would be best.

Two combos or wye+45 in series might do what you need and then a combo for the vent.

Are you planning to have the output of the dual whatever in the horizontal plane or vertical? I am not confident that a double whatever adds much for you.
 

Reach4

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So that mounted vertically would have an elbow at the bottom to go from vertical to horizontal. I have to think there would be a better way.
 

Allison

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Yeah correct, I am limited on space. I am planning on running a horizontal drain perpendicular to the joist direction then connecting to the main stack. I'm trying to keep the connections to the horizontal drain as much in the joist space as possible (so the wall that will eventually hide the drain does not have to be exceptionally wide, this is in a currently unfinished basement). I've considered using two wyes in series but then it is tight to keep them in the same joist as the toilet drains, and tight again to find a spot to vent before the next connection (shower and tub). It might be possible but I'm trying to explore all the options/make sure I can source all of the potential fittings.
 

Reach4

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In the downstream joist bay, I am thinking of a wye somewhere between horizontal and tilted 45 degrees. Maybe a 4x3 closet bend coming down, and a 45 or 22.5 to make those things connect.

Maybe make a top view sketch showing the closet flange locations and the joist locations. Somebody may have the better suggestion based on that.

You could buy some smaller fittings to play with as a model of what you implement. Perhaps sand those smaller on the ends to fit together easily for visualization.
 

tmcnutt18

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One 2" vent would vent both toilets. I would use wye fittings. You only need 3" and they make 4x3 closet flanges. Toilets typically have a 2" trapway dropping into a 3" line.

Terry,

Would I be able to to use toilet vent as a wet vent and have back to back vanity drains connect to toilet vent? If so would size need to increase? I’m trying to keep joist space open for HVAC duct.

Thanks,
Tom
 
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