Are my DWV vents adequate for a new bathroom install

[James Borjas]

Hi all, hope everything is going well. This is in WA state.

I am adding a 9' x 3' full bathroom and stacked washer/dryer to a finished space above the garage. I have attached the layout of the space and my proposed plan for waste lines and vents.

Is the venting I have adequate (or redundant?). Each vent line requires drilling through a 24" x 6" beam to get into the wall , so I would rather eliminate any unnecessary vent lines if at all possible. All drainage lines will meet up together under the subfloor, turn 90 degrees and travel through the 3" main line to the house.

All waste lines will be properly sized (3" for toilet, 2" for washer/shower, 1.5" for lav sink) and 2" venting will be used throughout.

Thank you so much for any constructive criticism or feedback.

 

[wwhitney]

In your drawing you can eliminate the rightmost vent that is dedicated to the shower. Then the lav would wet vent the shower and the WC. The trap arm on the shower still needs to meet the usual requirements (where the vent connection is the horizontal connection to the lav drain).

The lav vent and lav drain need to be 2" for wet venting the WC. The washer vent only needs to be 1-1/2".

Where is this 6x24 beam and can you really not avoid drilling it?

Cheers, Wayne

 

[Sponsor]

 

[Terry]

The drain for the washer can be in the wall behind the toilet.
The lav vents the shower.
If you fir the wall behind the lav, the waste and vent can miss the beam. Have you considered a cabinet there to hide the pipes?
I don't see enough height there to drop the toilet straight down into a wye or combo fitting. A santee spreads the poop both directions. I now, I've had to cut them out before and replumb them. Someone else did the original work, not mine.

I don't see how a bathroom with a shower, toilet and sink can work being only 36" wide. In fact, a 36" pan after the drywall goes up is more like 34.75" in the clear.
You need 24" in front of the toilet, and somehow need to squeeze into the shower past the sink.

 

[James Borjas]

In your drawing you can eliminate the rightmost vent that is dedicated to the shower. Then the lav would wet vent the shower and the WC. The trap arm on the shower still needs to meet the usual requirements (where the vent connection is the horizontal connection to the lav drain).

The lav vent and lav drain need to be 2" for wet venting the WC. The washer vent only needs to be 1-1/2".

Where is this 6x24 beam and can you really not avoid drilling it?

Cheers, Wayne

Thank you very much for the insight and reply, much appreciated. It’s great to know the shower vent is redundant. That was going to be the most challenging vent given the beam in the way.

The beam runs along the entire middle of the building exactly on center below the 9’ back bathroom wall that bathroom sink will be installed on. In fact, the bathroom sink wall is framed directly on top of the beam (you can see it in my last picture where I went to open up the wall and the beam is in the way of drilling down to the bottom plate of the framing).

If anyone has any suggestions for ways to avoid drilling through the beam that’d be incredible. Since the garage is below the bathroom and I don’t care how the garage ceiling looks, I thought about running the pipes below the beam and venting around the beam. However, due to height constraints between the bathroom floor and the garage door opener below it, I would have to run the vents from the waste line at 35 degrees above horizontal for about 12” to bypass the beam, before going directly upwards to the roof. My understanding was that anything less than 45 degrees was not okay for vents until I cleared the height of the bathroom sink, hence why I chose to go through the beam. It’s entirely possible there’s a better way I haven’t considered.

 

[James Borjas]

The drain for the washer can be in the wall behind the toilet.
The lav vents the shower.
If you fir the wall behind the lav, the waste and vent can miss the beam. Have you considered a cabinet there to hide the pipes?
I don't see enough height there to drop the toilet straight down into a wye or combo fitting. A santee spreads the poop both directions. I now, I've had to cut them out before and replumb them. Someone else did the original work, not mine.

I don't see how a bathroom with a shower, toilet and sink can work being only 36" wide. In fact, a 36" pan after the drywall goes up is more like 34.75" in the clear.
You need 24" in front of the toilet, and somehow need to squeeze into the shower past the sink.

Thank you for offering to edit the title, much appreciated. And for your reply as well. The title should ideally be “Are my DWV vents adequate for a new bathroom install?”

Thank you for the suggestion about the washer drain being able to be in the wall. This is a great idea, I had not considered the washer drain line could be on the side of the “closet” as I’ve not seen it done that way before, but it would bypass the beam entirely that way. I will either add a cabinet/fir or frame out that dividing wall with 2x6 or 2x8 to fit to the vent inside the wall after your suggestion.

The 9x3 bathroom will be tight. Those are the interior dimensions of the bathroom after drywall/backerboard. The lav sink will be a 10” deep wall mounted sink to allow clearance to the toilet (my drawing does not depict that, sorry). I installed the exact same bathroom layout (excluding washer dryer) once before and it was approved. It’s not luxurious but gets the job done. I greatly appreciate all the feedback and criticisms, they are things I would not have considered!

I don't see enough height there to drop the toilet straight down into a wye or combo fitting. A santee spreads the poop both directions. I now, I've had to cut them out before and replumb them.

Do you mind to elaborate on this? It seems quite important but I missed what exactly it is referring to besides the toilet drain. I’m sure it’s my lack of experience not following you. Thank you.

 

[wwhitney]

The beam runs along the entire middle of the building exactly on center below the 9’ back bathroom wall that bathroom sink will be installed on.

Thank you, I missed the small yellow type in your photos.

You certainly can't drill that beam vertically. You might be able to drill the beam horizontally in the middle, but being sure that would be allowed would require some more thought. You are best off figuring out a way to run all the DWV without drilling the beam at all.

For the sink, you'll have to put the vertical drain below the san-tee outside the wall to miss the beam (maybe leave 1/4" clearance between beam and pipe). Space is obviously tight in the 36" dimension, but you could use a shallow pedestal sink or a shallow vanity to hide the pipe. Then at a height above the beam, the san-tee and vent can be within the wall.

Not quite following where your laundry standpipe is going to be, but again, the drain below the laundry san-tee that has to penetrate the floor needs to avoid the beam.

Cheers, Wayne

 

[James Borjas]

Thank you, I missed the small yellow type in your photos.

You certainly can't drill that beam vertically. You might be able to drill the beam horizontally in the middle, but being sure that would be allowed would require some more thought. You are best off figuring out a way to run all the DWV without drilling the beam at all. Alternatively I realized I could frame out a false wall at the back of the washer closet for the drainage since I have an extra 6” o

For the sink, you'll have to put the vertical drain below the san-tee outside the wall to miss the beam (maybe leave 1/4" clearance between beam and pipe). Space is obviously tight in the 36" dimension, but you could use a shallow pedestal sink or a shallow vanity to hide the pipe. Then at a height above the beam, the san-tee and vent can be within the wall.

Not quite following where your laundry standpipe is going to be, but again, the drain below the laundry san-tee that has to penetrate the floor needs to avoid the beam.

Cheers, Wayne

Thanks Wayne! You are right that the best way would be to avoid the beam altogether. I think with a combination of yours and Terry’s suggestions I may be able to.

For the washer, Terry suggested to relocate the drain into the dividing wall between the bath and washer closet, so that will prevent me from having to worry about the beam. The drain would just be on the right hand side of the washer “closet” but you can’t see back there anyways. Then I can run the vent vertically in the new dividing wall between the bathroom and washer. I also realized I have enough space behind the washer/dryer to frame an additional 2x4 wall for the plumbing to run in as an alternative, though I prefer the dividing wall suggestion.

Removing the unnecessary shower vent I had prevents needing to drill in the beam as well. Finally, if I incorporate your last suggestion to bring the bottom of the bathroom sink into the room, I should avoid it everywhere. Really appreciate the helpful ideas that have been given!

 

[Noah Simpson]

Is the beam made up of LVLs? You should be able to look on the manufacturer's webpage and they will have a design document indicating where/how many/how big the holes can be if you need to drill it.

 

[James Borjas]

Is the beam made up of LVLs? You should be able to look on the manufacturer's webpage and they will have a design document indicating where/how many/how big the holes can be if you need to drill it.

Yes, thank you. I hope I don’t have to end up drilling through it with the suggestions I’ve been given but that will be helpful in the event it is unavoidable.

 

[wwhitney]

Terry suggested to relocate the drain into the dividing wall between the bath and washer closet

FWIW, if you are using a recessed wall box that also has the water supplies, it's good to put them in a place you can reach in to shut off the water. E.g. with a 3-4" gap between the machines and the wall, and the recessed box close enough to the front that you can reach the water shutoffs.

Cheers, Wayne

 

[James Borjas]

In your drawing you can eliminate the rightmost vent that is dedicated to the shower. Then the lav would wet vent the shower and the WC. The trap arm on the shower still needs to meet the usual requirements (where the vent connection is the horizontal connection to the lav drain).

The lav vent and lav drain need to be 2" for wet venting the WC.

Cheers, Wayne

Question: for the fitting in the red box on my diagram (joining the vertical lav drain into the horizontal shower drain), am I still able to use a 2" Wye (with a 45 degree bend attached going up to the lav) to join the lav drain line into the main waste line, since it is wet venting the shower and WC?

I was putting together the rough in up on my ladder after everyone's extremely helpful advice and realized I was not 100% confident that the fitting shouldn't a sanitary tee instead of the wye I had planned due to the wet venting. Thank you!

 

[James Borjas]

FWIW, if you are using a recessed wall box that also has the water supplies, it's good to put them in a place you can reach in to shut off the water. E.g. with a 3-4" gap between the machines and the wall, and the recessed box close enough to the front that you can reach the water shutoffs.

Cheers, Wayne

Thank you! This is helpful; the type of thing I would likely otherwise only realize was very inconvenient when something breaks, water is leaking everywhere, and one can't get to the shut off...

 

[wwhitney]

Question: for the fitting in the red box on my diagram (joining the vertical lav drain into the horizontal shower drain), am I still able to use a 2" Wye (with a 45 degree bend attached going up to the lav) to join the lav drain line into the main waste line, since it is wet venting the shower and WC?

Yes. Typically the shower drain would join the lav (first) and the WC via a horizontal (2% slope on both inlets) wye.

So ideally you would be able to pick a line for the horizontal drain perpendicular to the joists such that both the lav drain (entering the floor system against the beam) and the WC are far enough off the line to leave space for a 90 (LT for the lav drain) to point at the wye. And also within one u-bend offset of the shower drain. But that may not all be geometrically possible at once, in which case you'd have to compromise on one or the other or use a small bend on the horizontal.

Cheers, Wayne

 

[James Borjas]

Yes. Typically the shower drain would join the lav (first) and the WC via a horizontal (2% slope on both inlets) wye.

So ideally you would be able to pick a line for the horizontal drain perpendicular to the joists such that both the lav drain (entering the floor system against the beam) and the WC are far enough off the line to leave space for a 90 (LT for the lav drain) to point at the wye.

Cheers, Wayne

Awesome, thank you! That is incredibly helpful.

Any problem in your viewpoint of having the main horizontal drain line run directly underneath the shower and toilet drains and have them connect directly down to the horizontal line with wyes oriented on their back? (The orientation shown in the blue circles fitting from the code manual)?

I may have misread your last comment but I got the impression you suggested to offset thee horizontal line so it is not directly under the toilet/shower and attach the wye like the red circled wye from the code diagram and wanted to understand why one may be better than the other. Thanks!

 

[wwhitney]

Any problem in your viewpoint of having the main horizontal drain line run directly underneath the shower and toilet drains and have them connect directly down to the horizontal line with wyes oriented on their back? (The orientation shown in the blue circles fitting from the code manual)?

Comments:

That illustration must be from an IPC-based document, as the UPC (in force in WA) requires a 2" dry vent for any WC. Thus practices illustrated may not be appropriate for the UPC. Just something to be aware of when looking at sources, whether they are based on the IPC or UPC.

I assume when you mention shower wye you mean the shower/lav wye, which I'd be more inclined to call the lav wye. The shower itself absolutely can not connect via an upright wye, as its trap needs to be vented according to the usual requirements, including no more than one pipe diameter fall from the trap outlet to the vent connection (the lav wye). So the elevation of the trap outlet is the elevation of the upstream end of your horizontal drain.

Then the only question is the orientation of the wye where the lav comes in and the wye where the WC comes in (since the WC has an integral trap and is self-siphoning, so it is not subject to any vent elevation requirements). [If you had a fourth fixture, like a tub or floor drain, it would have to use a horizontal wye, for the reasons in the previous paragraph.] Everyone agrees that they can both be horizontal, like your red circle. I think it is widely agreed that the lav can be vertical, like the blue circle. There is some language in the plumbing section of the IRC (residential code) that say wet vented fixtures have to connect on the horizontal, but that language is not in the UPC or the IPC.

So if you are subject to the plumbing section of the IRC (depends on whether the jurisdiction has adopted it, not sure how likely that would be in a jurisdiction using the UPC, since the IRC is based on the IPC), then the WC connection would have to be horizontal. Otherwise, I don't see any code restriction. But some will say that horizontal for the WC will still perform better, and I don't have an opinion on that. Horizontal is conventional and a safe choice. Since as far as I can see there's no particular reason to favor one location of the horizontal line over another, per your photos (unless you've subsequently drilled the joists), I suggested going with the offset and horizontal wyes.

Finally a quick note: if the WC is closer to the horizontal line than in the diagram shower, you can omit the 45 elbow on the wye and just rotate the closet bend 45 degrees to point into the wye.

Cheers, Wayne

 

[James Borjas]

I assume when you mention shower wye you mean the shower/lav wye, which I'd be more inclined to call the lav wye.

Yes, I meant the lav wye. Thank you so much for both answering my question and being able to interpret what I should have called it.

The shower itself absolutely can not connect via an upright wye, as its trap needs to be vented according to the usual requirements, including no more than one pipe diameter fall from the trap outlet to the vent connection (the lav wye). So the elevation of the trap outlet is the elevation of the upstream end of your horizontal drain.

Thank you! I was thinking about this last night trying to figure out why my idea didn’t quite seem right. Your explanation helps me understand why specifically it’s wrong so I can apply that to future situations too. Much appreciated.

Then the only question is the orientation of the wye where the lav comes in and the wye where the WC comes in (since the WC has an integral trap and is self-siphoning, so it is not subject to any vent elevation requirements). [If you had a fourth fixture, like a tub or floor drain, it would have to use a horizontal wye, for the reasons in the previous paragraph.] Everyone agrees that they can both be horizontal, like your red circle. I think it is widely agreed that the lav can be vertical, like the blue circle. There is some language in the plumbing section of the IRC (residential code) that say wet vented fixtures have to connect on the horizontal, but that language is not in the UPC or the IPC.

See as far as I can see there's no particular reason to favor one location of the horizontal line over another, per your photos (unless you've subsequently drilled the joists), I suggested going with the offset and horizontal wyes.

Finally a quick note: if the WC is closer to the horizontal line than in the diagram shower, you can omit the 45 elbow on the wye and just rotate the closet bend 45 degrees to point into the wye.

You’re absolutely right, there’s no reason to favor any particular placement of the horizontal line over another. I will offset the line and go with horizontal wyes; I haven’t drilled anything yet. Thank you so much for helping walk me through this. I feel much more confident because I understand why it has to be a certain way (or not) now. That’s been one of the hardest parts for me learning all this stuff - understanding if a choice when seeing a system was personal preference or a requirement, and you cleared that up really well for me. Wish I could buy you a beer at the very least!

 

[James Borjas]

Comments:

That illustration must be from an IPC-based document, as the UPC (in force in WA) requires a 2" dry vent for any WC. Thus practices illustrated may not be appropriate for the UPC. Just something to be aware of when looking at sources, whether they are based on the IPC or UPC.

Thank you, I should have checked that.

One final question. As I’m assembling the system I realized I had a last doubt about the main drain line that I am connecting each of the fixtures into. Does the main line need to be 3” throughout because the toilet and shower are venting via the lav? Or is it okay to use a 2” main line from the shower until past the lav wye, and an increaser to change from 2” to 3” before connecting the WC wye?

 

[wwhitney]

The lav trap arm can be 1.5". Everything else can be 2", except the drainage path of the WC. That means the WC wye could be 3x2x3, which doesn't exist, so you could use a 3" wye with a 3x2 bushing in the straight inlet that is receiving the lav/shower drain.

If there were a cleanout requirement, it would make sense to extend the 3" as far towards the shower (or the lav) as needed to get to an accessible cleanout. But I'm pretty sure that the UPC doesn't require a cleanout on an upper story horizontal branch.

Cheers, Wayne

 

[James Borjas]

The lav trap arm can be 1.5". Everything else can be 2", except the drainage path of the WC. That means the WC wye could be 3x2x3, which doesn't exist, so you could use a 3" wye with a 3x2 bushing in the straight inlet that is receiving the lav/shower drain.

If there were a cleanout requirement, it would make sense to extend the 3" as far towards the shower (or the lav) as needed to get to an accessible cleanout. But I'm pretty sure that the UPC doesn't require a cleanout on an upper story horizontal branch.

Cheers, Wayne

Awesome, much appreciated. I’ll be adding a 3”clean out as soon as the 3” horizontal main line to the house turns 90 degrees to head to the main building. Thank you.