Venting for 1st floor bath when second floor bath ties into 1st floor bath via horizontal waste line

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Djd275

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Hi all,

I am in the process of adding a second floor bathroom and completely redoing the first floor bath and need some advice for how to vent the first floor bath/ kitchen sink (current venting cant not be left as is, as it vents straight out of the side of the house near a patio- house built in 1890s). I have been reading about wet vents, but am unsure if my situation would qualify as a wet vent/ work, since the 2nd floor bath would make a toilet not be the last fixture. The area I live in has no code I have to specifically follow, but I would like to keep it as close to national code as possible. There will be a rooftop patio over the first floor bath so, I can not add a second roof vent near the 1st floor bath or have any vent pipes that go above the flood rim level until about 5 feet from all the fixtures in the 1st floor bath. See attached picture for the basic layout of the two baths. Basically the second floor bath has a tub, shower, sink, and toilet connected to a 3" vertical stack that then turns and runs horizontally (1/4 slope) in the crawl space until it reaches the 1st floor bath 3" waste line that runs to the septic system. 1st floor bath consists of a tub/shower, sink and toilet. Also connected in the same area of the 1st floor bath fixtures will be a washing machine and kitchen sink. The second floor bath is vented normally via a 2" pipe which penetrates the roof. My thought to vent the 1st floor bath is to "wet vent" it by using a sanitary tee to tie a 2" vent line (listed as possible vent in the picture) into the 3" waste line and then connect it to the 2nd floor bath vent which goes out of the roof. Vent from first floor bath will be connected just above where vents of 2nd floor bath tie in. This vent will be vertical or have 1/4 slope back to the waste line for the entire 35 foot run. Since the kitchen sink will have about a 10 foot trap arm, I am planning on adding an AAV near the kitchen sink as well.
If additional information is needed, please let me know and I will try to add it. This is my first time posting on a form like this, so please let me know if anything needs to be changed.
Thank you in advance for any advice/ comments.

bath venting.jpg
 

Jeff H Young

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the drawing isn't very good but in general on first floor I'd branch the shower off the toilet line by wet venting and then vent all the fixtures together to the 2 inch vent and run up to the second floor tie in. not knowing your code but looking at your drawing Id continue on the stack going to upper floor and stay 3 inch all the way through roof since I don't know which codes you use
 

Djd275

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the drawing isnt very good but in general on first floor Id branch the shower off the toilet line by wet venting and then vent all the fixtures together to the 2 inch vent and run up to the second floor tie in. not knowing your code but looking at your drawing Id continue on the stack going to upperfloor and stay 3 inch all the way through roof since I dont know which codes you use
Jeff, Thank you for the reply.
I apologize for the poor drawing, drawing has never been my strong suit. I am not sure that I understand what you are suggesting though. I can tie the shower into the toilet line, however they are on opposite sides of the main soil line, so I am not sure if it would benefit much as the shower would not have a normal vent that goes above its flood rim level in a short distance. Due to the structure of the house I can't put in any vent lines above the 1st floor (all vent and soil lines must stay in crawl space) until about 5 feet upstream of the kitchen sink tie in to the main soil line (this is where it would rise above the flood rim level of the 1st floor fixtures). So if my understanding of wet venting is correct, all fixtures would be wet vented through the main soil line until it hits the 2" vent (labeled as possible 2" vent) that would tee into the vent through the roof above the 2nd floor bath fixtures. I have attached a top down view of the layout of the fixtures to hopefully better explain. Where I am mainly getting confused is that everything I have read on wet venting requires the toilet to be the last fixture. In my case I would have the entire 2nd floor bath upstream of the "end of the wet vent". So, is it ok to have the 2nd floor bath come straight into the end of the main soil line that goes to the septic system with a vent line pulled off in-between the 2 baths? Is a vent line between the baths really even necessary or can the 1st floor fixtures all be wet vented to the vertical stack that drains the 2nd floor bath since it continues through the roof as a vent?

top view bath plumbing.jpg
 

John Gayewski

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You can't wet vent anything across the building drain. So you need a vented branch off of both sides. One wet vented branch containing the toilet and sink,and one vented branch for the shower. You need to run vents in walls or ceilings to get to atmosphere You can use aav's but I actually don't think they will work that well without more atmospheric venting.

I'm pretty sure Missouri is ipc (which will allow aav's) yes you do have a code adopted by your state, your county should provide enforcement if you are not in a city, but many either don't or aren't made aware that there's a project that needs inspection.
 

Terry

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The downstairs plumbing needs to be vented separately from the line that carries the upstairs bathroom waste.
Looking at the drawings, it isn't clean that any of what you're supposing is correct.

You can't just wye into a waste line that carries water from a floor above and expect the venting to work.
Every p-trap and arm needs venting coming off the top, not the bottom somewhere.

index.php


dwv_b2.jpg
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I have in the past, cut drywall in the floor above, and dropped a vent down to the lower floor to use.
 

Djd275

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Thank you for the replies. I was figuring that may be the case.
Sadly I cant run the vent lines in the walls for the 1st floor. There is a roof top patio above the bath which leaves no room for connecting the pipes above the bath and 3 of the walls are load bearing and old/current exterior walls that I can't get the pipes into/ notch the vertical supports for the pipes to run. So any venting will have to run 3-5 feet under the floor before it can turn vertical and get above the flood rim level of the fixtures. I drew up another possibility that may be better, although I know is probably is not ideal. I am wanting to follow national code/ Missouri's. My county does not provide enforcement of the codes, but I want to follow them incase that ever changes and so I know it will function properly. Going off of John's comment, I can make the toilet wet vent through the sink and the sink's vent would run horizontally (with 1/4 slope) 3 feet before turning vertical and tie into an atmospheric vent (2"). The tub/shower would tie into the same vent above the flood rim level (again after about a 3' horizontal run). The kitchen sink (in an island) would have an AAV and drain into a shared drain line with the washing machine which would have a vent that goes to atmosphere after 5 feet horizontally before turning vertical. All vent lines would have 1/4" slope back to drains and run about 3" above the drain line. Hopefully the picture helps (I wasn't too sure the best way to draw it). Thank you again for the advice and your patience in helping me figure out my options.
 

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John Gayewski

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Sounds like you need to build another wall to run some piping in or just fur the current wall(s) out to accommodate piping.
 

Jeff H Young

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all of the fixtures need vents on first floor in some manner. the " possible 2 inch vent " can receive vents from any or all of the others if your able to rout them
 

Djd275

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Looks like I'm SOL for any kind of venting being done under the 1st floor. Although it will cause a fair amount of demo on finished walls/ceilings, I believe I have figured out a way to vent the sink and toilet by running them up a new wall until they hit the ceiling. They would combine in the ceiling and then run horizontally until it gets to an area where it can exit the roof. However, for the tub/shower the main soil line runs on the opposite side of the tub drain and wall I have to run a vertical vent in. Is it ok to have a 90 degree bend where the vent tees in which would then turn the drain line back to run slightly under the trap, centerlines of the trap arm would be minimally offset. I want to make sure this isnt in creating a S trap which would allow the trap to empty. I only have about 4-5" of room to work with due to the main floor joist which cant be notched and the foundation wall below. Please see attached picture for the tub drain/vent. Thank you again for all the comments and replies, I greatly appreciate it.
 

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