Re-plumbing bathroom and soil stack


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Old 02-24-21, 08:48 AM
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Re-plumbing bathroom and soil stack

Hello. This forum been helpful in the past so I want to run by you my plan for replacing drain and vent pipes in my bathroom and connecting it to the main sewer line.

Location: Minnesota.

Here is the picture of what I'm planning to do with indication of size and type of every fitting.




Several questions:
1 - Is everything looks correct on the diagram? I have to use couple of 22 bends right under the flange to slightly redirect the pipe as there is concrete wall right under the flange. I might use couple of 45 instead if I determine that i need to move it a little more.
2 - The pipe that goes from the kitchen serves a sink/DW combo and right now this pipe is 1 1/2. Shall that be increased to 2? Looking at 703.2 table it should be 2'' since kitchen with DW is 2 DFU according to 702.1
3 - the size of the horizontal vent. 703.2 says that 1 1/2 pipe can vent 8 DFU which is greater than 5 (combined kitchen/DW + lavatory + tub). Am I correct? Can I use 1 1/2 pipe here or shall it be 2?
4 - the size of the vent that goes to the roof. 904.1 says the vent shall be no less that max required sewer. In this case according to 703.2 my largest required in 3'' for the toilet. Mean vent shall be 3 as well?

Thank you for help.
 
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Old 02-24-21, 10:02 AM
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I'm a bit confused as to which pipes are vertical and which are horizontal, so I'm not sure I'm looking at it completely correctly. Can you sketch out a plan view (rooms looking down) on how everything is laid out?

1) No problem with using a few elbows to adjust the toilet position
2) Some codes are changing to increase the kitchen drain to 2". I see no reason not to upgrade to 2" as you'll definitely see fewer clogs in the future.
3) 1.5" pipe is fine for the DFUs you have. BUT, the kitchen can't wet-vent through the bathroom group, so it'll need its own vent. The bathtub can wet-vent through the vanity sink, but with the kitchen drain between might change that rule. It's a setup I'm not familiar with, so I'm not 100% sure.
4) As long as you have a stack vent already through the roof, that code ref doesn't apply. Your vent only has to cover the DFUs on that branch. So you're good with a 2" vent - though some snow-filled areas require upsizing to prevent freezing.

Some other comments:
* The san tee at the top left is upside down. Vent tees are installed so the sweep follows the airflow.
* Can you do something else other than 3 90deg fittings on the bottom right? If you have that much change in direction, you need to add a separate cleanout, which you probably don't want or need.
* the 2 90deg fittings to the vanity should be long-sweep 90s
* At the bottom, the 4x4x2 san tee should probably be a wye or combo wye. If it's a vertical stack at that point, a san tee is fine, but a wye is preferable if usable.
 
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Old 02-24-21, 11:21 AM
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Thank you for your response.

I should've uploaded real life picture of the existing situation. Pretty much every pipe is vertical except couple of short runs of vent pipes and one short run of the drain pipe under lavatory.




On first diagram blue = venting, black = drainage

3 - I haven't thought about that. I was originally trying to replicate existing layout where kitchen drains into main 4'' soil stack and I assume in this case vent directly through the 2'' roof vent. But then I changed the design. Looks like I will have to go back. It would just add one more 4" wye to the main stack dedicated for kitchen drain. And I've just realized that kitchen and bathtub got switched around on the diagram.
4 - Yes it is an existing vent (which frankly I was going to replace with PVC of the same size, it is iron now). But if leaving it as is allows me to have 2'' there then I'm fine with it. If I re-route kitchen drain to main 4'' soil stack, DFU would be 5, so 2'' vent still should be enough.

Can you do something else other than 3 90deg fittings on the bottom right? If you have that much change in direction, you need to add a separate cleanout, which you probably don't want or need.
Does it matter if it is a vent pipe?

[QUOTE* At the bottom, the 4x4x2 san tee should probably be a wye or combo wye. If it's a vertical stack at that point, a san tee is fine, but a wye is preferable if usable.][/QUOTE]

Yes it is vertical at that point, but I see no problem with changing it to wye
 
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Old 02-24-21, 04:03 PM
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Re-designed the diagram going back to original version more or less replicating existing piping.

1. Added reducer for the vanity vent from 2 to 1.5
2. Put 2 wye on the main stack. One for kitchen and not for lav/bathroom. I assume that now I don't need a separate vent for the kitchen. Or do I?
3. that 3'' 90 bends for vent. I will have to probably replace 4x4x3 san tee with wye and instead of 90 use 45s and/or 22s to avoid 90 degree angles.




 
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Old 02-25-21, 10:27 AM
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Welded steel drain pipes... haven't seen those before (though I do have welded steel heating pipes in my house).

The updated layout looks good. Thanks for the pics.

* I can't tell if there's a cleanout already on the stack, but I would add one if there isn't.
* Since this is your main stack, yes, the vent out the roof needs to match - so a 4" vent.
* I would plan on venting the kitchen sink now or in the future. Using a 2" drain alleviates the desperate need for a vent, but a vent is still required in most codes.
* For what it's worth, the wye to the bathtub is usually done using a combo wye (wye + 45deg street elbow). Fewer pieces - but will do and work the same as you have it.
* Where you connect to the existing sewer, be sure to use a shielded no-hub coupling (similar to the ones already used). Many people go for the rubber Ferncos, though they don't meet code and can cause clogging issues.

Lastly, i would do away with the steep-slope kitchen drain. Move the wye up and let the drain run horizontally (with a 1/4" per foot fall), and then combo-wye into the stack. Same with the tub, though that's basically how it's run now - just make sure it has a proper slope.
 
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Old 02-25-21, 12:00 PM
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Uffff, 4'' for the vent? Isn't is an overkill? I thought it should match required (not what is actually installed)? And i believe required main stack is 3.
 
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Old 02-26-21, 09:44 AM
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Oh - sorry if I misunderstood. All the vents through the roof need to contain the same area as the main drain. So in most cases, if you have a 3" drain, your vent needs to be 3". I see no reason to upsize any drain to 4".
 
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Old 03-01-21, 11:04 AM
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Right but isn't the code says the vent shall be same as required drain, not same as existing in case it is bigger than required?

Any thoughts how can overcome those 90 bends that go from main stack to vertical vent? I need to get over that wall somehow. Do you think Y instead of T would give me a better angle?

Also a question - can combo Y be placed not on its side, nor vertical but in this in-between position sorta like at 45 angle?
 
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Old 03-01-21, 03:00 PM
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Tie the lav right into that bathtub arm. That will take care of lav and tub vent as long as tour runnung vent for lav like your picture

vent for toilet needs to be only 2" and ties in to the 2" sink vent you show.

yes stack will be 3"
 
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Old 03-20-21, 03:35 PM
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Just wanted to say thank you and show the final result.

Had to change the drain from the tub/lav a little but overall everything was as planned thanks to your advises. Kicking myself though for cutting a vent pipe little too short and having to use the coupling but oh well. And my priming job wasn't as clean towards the very end (vent pipe) as I was at wits already and it wasn't very convenient location to move the swab around.

One thing that is left is to put new toilet into its rightful place.




 
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Old 03-20-21, 05:50 PM
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Looks great, nice clean work!
 
 

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