Residential DWV Layout Questions

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Goodimike

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First off, I want to thank everyone for their help with my plumbing layout thus far. I've learned so much from you all.

We are currently renovating our upstairs and adding a new laundry room, 1 full bathroom group for kids, and 2 lavs, and a soaker tub to the master bathroom. I am writing this post to double check my plumbing layout is up to IPC Code and will work efficiently. I have already posted questions about dry and wet venting which have been answered and I feel confident the venting layout. Everything is sloped 1/4'' for 2'' and 1/8-1/4' on the 3'' runs. I have on short run (3 feet) that is 1/16'' on the long toilet run which is okay I hope.


This is my updated attempt at a 2.5D drawing of the 2nd story plumbing layout. This includes vents and fixture drains:
9F65D45B-7CA3-473A-9C86-AB2BADA95264.jpeg


Here is the horizontal layout from above (not including vents):

image_6483441.JPG




Here is the Proposed Master Bathroom Layout:

AB55F925-14D9-4428-87AB-71FC6EE631C2.jpeg

For the Master Bathroom I am currently trying to figure out a better way to run drainage for the existing toilet and the new lav that are to the left and to the right respectively of the main 3" stack. Both of these fixtures are within 5 feet of the main stack. The way the house was originally plumbed had the most downstream toilet going into a long sweep 90 a foot or so of pipe and then another 90 leading to the main 3"

Here is the original layout before it was modified (this is all horizontal plumbing except 4 x 3 WC 90):

image_6483441 (2).JPG


Picture of most downstream Toilet (Left) and Lav (Right) which are within 5 feet of main stack (this is all horizontal plumbing except 4 x 3 WC 90):

image_6483441 (1).JPG



My concern is that both the downstream toilet and the most downstream lav turn 180 degrees in a relatively short distance. I know there is likely a better alternative to this current layout, but not sure how to go about it without tying directly into the 3" stack (i'm hoping to avoid this as it seems daunting for DIY and the rest of the downstairs plumbing vents through this stack and I've never used shielded couplings). I thought that maybe I could connect the lav drain to the 2'' at a >45 angle (nominally vertical) to eliminate a horizontal 90 so there would only be one horizontal 90? I may or may not have enough joist space for this, but is this allowable or does it add any benefit? I believe the toilet is vented by the 3'' stack, is that correct? I'm not sure if the new lavs and tub affect the toilet venting since they connect on the horizontal after the toilet.

From what I've read on these forum it looks like under IPC a 3'' drain needs to be used whenever another fixture drain connects to the 2'' washing machine drain. Is that correct? Does this also apply to UPC or just IPC?


I know a cleanout is needed after >135 change in direction on the horizontal, but not sure where to put an accessible clean out unless it is to be located in the tile floor and not in a wall.


Hopefully My post makes sense. Sorry for the poor drawings and thank you for your help with this project.
 
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Jeff H Young

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the lavies and tub are no issue at all . main issue to me me is the wash machine messing up the horrizontal wet vent oportunities, and what looks like horrizontal dry vent below the 6 inches above fllod level on the uppermost stream toilet
 

Goodimike

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the lavies and tub are no issue at all . main issue to me me is the wash machine messing up the horrizontal wet vent oportunities, and what looks like horrizontal dry vent below the 6 inches above fllod level on the uppermost stream toilet
Hi Jeff, are you saying the Washing machine drain is negatively affecting the went venting of the bathroom upstream of it or downstream of it? Also, I’m trying to figure out which dry vent you are referring to. I have a post on this forum called wet venting where I drew the layout. It is a horizontal wet vent. I’ll see if I can post a picture. I went with the layout at the top of the drawing.
 

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Jeff H Young

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Didnt realize youve got several options ? Im talking about the first sketch in post 1 has w/m running through wet vent cant do that and the uppermost toilet appears to have a vent in the joist bay that wont work either
 

Goodimike

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Sorry, the sketch is not complete. The upstream toilet and tub is being wet vented by 2 lavs that are not shown on the top picture. I just drew out the horizontal plumbing under the floor and nothing else. The washing machine has a 2” common vent going through the roof that it shares with the most upstream lav, but I may be misunderstanding what you are meaning. Given that the washing machine is dry vented and the upstream toilet is horizontally wet vented by a lav, where should the W/M drain connect to the 3” drain?

There is currently no vent for the most downstream toilet which is the way it originally when I found it. I’m assuming the 3” stack was used to vent it? If I need to add a new vent to the toilet then I believe I can.
 
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Jeff H Young

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ok well the upstream toilet is actuall wet vented by 2 lavs not dry vented so thats portion is good. the downstream toilet would be fine except the wash machine needs to tie in to the waste line between the stack and first branch
 

Goodimike

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ok well the upstream toilet is actuall wet vented by 2 lavs not dry vented so thats portion is good. the downstream toilet would be fine except the wash machine needs to tie in to the waste line between the stack and first branch
Hi Jeff, thank you for your helpful responses. I may have to re think some things then. Tying the W/M drain in near the stack as you recommended will be very difficult due to many factors.
The most upstream bathroom group is wet vented by the lavs that has a 2” vent through the roof. The W/M has its own separate 2” dry vent going through the roof which is completely seperate of the bathroom group downstream of it. I know the toilet has to be the most downstream fixture when wet venting, but I thought that since the W/M has its own dry vent that the washer could connect downstream of the wet vented toilet. Could you help me understand the reasoning of why this set up will not work? Thank you again.
 

Goodimike

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I added a more detailed drawing which is hopefully easier to see the full layout of things.

I have a basement so if I need to create a vertical drain for the W/M through a wall and tie in at the basement level I can. I would consider this last resort, but it would likely be easier than tying in upstairs closer to the 3” stack.

Will adding a vent to the downstream WC fix the issue?
 
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Jeff H Young

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I added a more detailed drawing which is hopefully easier to see the full layout of things.

I have a basement so if I need to create a vertical drain for the W/M through a wall and tie in at the basement level I can. I would consider this last resort, but it would likely be easier than tying in upstairs closer to the 3” stack.

Will adding a vent to the downstream WC fix the issue?
yes thats the entire issue is venting the downstream toilet if you can vent it between the closet bend and the combi on the drawing you are good , Im hoping its not piped yet if that 3 inch is long enough and a wall is right above it thats all you would need , Just guessing but think that senario is doubtful
 

Goodimike

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yes thats the entire issue is venting the downstream toilet if you can vent it between the closet bend and the combi on the drawing you are good , Im hoping its not piped yet if that 3 inch is long enough and a wall is right above it thats all you would need , Just guessing but think that senario is doubtful
Thank you for the feedback Jeff. That makes sense. There is an unused lav to the left of the toilet that has a 1 1/2” vent that connects to the main 3” stack (I didn’t include it in the drawing). I might could tie into that? I’ll take a picture today and see what you think. Thank you.
 

Goodimike

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Here is the picture of the downstream toilet drain and unused lav drain next to it. Could vent the toilet by tying into this? Also there is a short wall to the right of the toilet drain that I might could run a vent through.


Also, doesn’t the W/M drain need to be 3” when another fixture drain is added to it according to IPC?
 

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Goodimike

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What are my options if I cannot vent the toilet? If I find another route for the W/M connection then the downstream toilet is properly wet vented?
 

Goodimike

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Jeff, I will plan on re-routing the W/M drain. Could I run the most upstream LAV's drain (the one that currently Wyes into W/M drain) to the 3'' horizontal drain where the W/M currently connects instead of the W/M? Thanks.
 

Jeff H Young

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sure nothing wrong with that the codes only have a problem with fixtures not associated with a bathroom so sinks and washing machines are 2 of the most common in a home , a w/m does dump a lot of water same with laundry sink and kitchen sinks a bar sink wouldnt hurt a thing but its prohibited too
 

Goodimike

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Here is a picture of what the horizontal branches look like in the basement and the connections. I’m planning running the W/M drain down from the 2nd story and attaching it to the 3” branch in the basement located to the right which is downstream of the 1st floor kitchen sink (common vented through roof) and the 1st floor island sink (vented with AAV). Does this setup look okay? If for some reason I am unable to run the W/M downstream of the two sink drains would upstream also work or would that be a bad idea?
 

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