Will this pass inspection, or additional vent needed?

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Ptwinter

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Newbie here, thanks for your help with my research.

I am building a one story addition that is not tied to the existing plumbing system. I have a couple of questions regarding the DWV in the UPC.

3" main drain pipe runs to 4" sewer. There are four connections to this drain pipe, from upstream to downstream, they are as follows:

2" shower into horizontal 3x3x2 wye. Branch is about 3' from p trap to drain pipe and is approximately 2' upstream from vent.
2" vent from roof into vertical 3x3x2 wye. Also, if possible, would like to have washer drain into the vent.
2" lav into 3x3x2 wye horizontal. This branch is about 8' from drain pipe and will be vented to main vent by 2" above ceiling and is about 2' downstream of the vent.
3" WC into 3x3x3 wye horizontal. This is about 2' to 3" drain and about 3'6" downstream of the vent

Questions: Do I need an additional vent upstream or downstream in this system? If needed, can it be tied into the existing vent?

under slab plumbing 2.jpg
 

Terry

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With UPC code the washer needs it's own vent, and the bathroom needs it's own venting. The washer can't be part of the bathroom wet vent. It's a pumped fixture, pushing way too much water for that to work.

The washer could wye in downstream of the bathroom.
The lav run with 2" could wet vent the toilet and the shower. You still need an end of the line cleanout. Sometimes that is at the lav, hidden in the cabinet and accessible.
 

wwhitney

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To be clear, what you have is fine as long as you tie the laundry in downstream of all 3 bathroom fixtures; it can't drain into the dry vent. And of course the laundry needs a vent, which could tie into either of the 2 dry vents shown.

In case it helps, the marked up picture below is my take on what Terry is suggesting, that you may eliminate the dry vent for the shower and let the lav wet vent it. The limit is that the shower trap arm, from the p-trap outlet to the wye where the lav drain joins is, needs to be no more that 5' in length along the pipe, and no more than one pipe diameter (2") in fall. The dashed blue is an alternate shower trap arm routing if it is currently over 5'.

And of course the laundry standpipe and trap is above the slab, just drawn in for reference.

Cheers, Wayne

under slab plumbing 2.jpg
 

Ptwinter

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Thank you Terry and Wayne! The one problem that I run into is the downstream end of the 3" combo wye for the WC is right against the foundation and I cannot, on this drain, go any further downstream due to that physical limitation. If the laundry drain has to be downstream, I would have to run a separate drain for the washer through the footing and tie it into the main 3" drain line outside the foundation, unless you have a better suggestion. I will check to see if the distance from p trap to lav wye is more than 5', otherwise, I will follow your suggestion.

All the best,
Phillip
 

wwhitney

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You could consider a layout as below, where red is 3", yellow is 2", and the red circle is the cleanout under the lav. At the foundation it would use a 3" wye and a 3" street wye. You'd need to check if that doesn't put the WC closet flange too far away from the foundation, or else enlarge your foundation hole enough for some of the branch of the downstream 3" wye to stick into it.

Cheers, Wayne

under slab plumbing 2.jpg
 

Ptwinter1

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You could consider a layout as below, where red is 3", yellow is 2", and the red circle is the cleanout under the lav. At the foundation it would use a 3" wye and a 3" street wye. You'd need to check if that doesn't put the WC closet flange too far away from the foundation, or else enlarge your foundation hole enough for some of the branch of the downstream 3" wye to stick into it.

Cheers, Wayne

View attachment 82838
I apologize that I didn't respond right away, I was having trouble recovering my password and ended up re-registering.

Can you let me know your thoughts on this layout?
Plumbing Layout.jpg
 

wwhitney

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My thought is that it is fine if the shower trap arm is no more than 5' and no more than 2" fall, which appears to me to be true.

I also think that the cleanout by the laundry is unnecessary if you install a 3" cleanout at the left (which is labeled but I don't actually see a fitting). I.e. that last 3" combo could just be a LT90. Or that combo could just receive the laundry drain, rather than extend to the cleanout. And that "main vent" is not required for anything, you just need the lav vent (2" for wet venting the WC) and the laundry vent (1.5").

On the number of required vents, that's related to this being an addition and ultimately connected to the existing DWV in the house. If it were a standalone building, it would need an aggregate vent area through the roof of at least a 3" vent, which that "main vent" at 2" would comply with (2" + 2" + 1.5" >= 3" in area). But the lav vent could instead be made 3".

Cheers, Wayne
 

Ptwinter1

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Wow, Wayne, you are amazing. Much thanks for the super quick response.

This is an addition whose plumbing is entirely separate from the rest of the house, other than it ties into the same sewer pipe. My hope was to keep the main vent where I have it labeled and tie the Lav and laundry into it. This would keep it from being right at the edge of the house in an exterior wall, as it would be at the location of the Lav. I assume, that I could follow your plan and put an elbow in the Lav vent and run the vent to a more favorable place to penetrate the roof. In that scenario, I could run the laundry vent through the roof. This would give this system the 2" Lav vent and the 2" laundry vent.
plumbing layout 1.jpg


Is the 90 off the WC, followed by another immediate 90 going to be OK?
 

Ptwinter1

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Wow, Wayne, you are amazing. Much thanks for the super quick response.

This is an addition whose plumbing is entirely separate from the rest of the house, other than it ties into the same sewer pipe. My hope was to keep the main vent where I have it labeled and tie the Lav and laundry into it. This would keep it from being right at the edge of the house in an exterior wall, as it would be at the location of the Lav. I assume, that I could follow your plan and put an elbow in the Lav vent and run the vent to a more favorable place to penetrate the roof. In that scenario, I could run the laundry vent through the roof. This would give this system the 2" Lav vent and the 2" laundry vent.View attachment 82934

Is the 90 off the WC, followed by another immediate 90 going to be OK?
plumbing layout 2.jpg
 

wwhitney

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This is an addition whose plumbing is entirely separate from the rest of the house, other than it ties into the same sewer pipe
When you say sewer pipe, are you using that in the technical sense, a drain pipe under the ground more than 2' outside the building footprint? Or are they connecting within the building footprint?

Certainly in the latter case, there'd be no reason to apply the 3" minimum vent through the roof rule separately to the addition and the existing building. I don't think there'd be any reason to treat them separately even in the former case, as the spaces are attached, but I'm not sure. If they were separate buildings, then I think the 3" minimum vent through the roof would apply to each of them separately.

Certainly you can route your lav vent through the ceiling framing/attic to exit the roof at a more favorable location.

Is the 90 off the WC, followed by another immediate 90 going to be OK?
It's not great, but it's OK, and it's no worse than the combo and the extra vent. I'm not sure if my latest drawing fits, but it avoids the net U-turn.

Cheers, Wayne
 

Ptwinter1

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When you say sewer pipe, are you using that in the technical sense, a drain pipe under the ground more than 2' outside the building footprint? Or are they connecting within the building footprint?

Certainly in the latter case, there'd be no reason to apply the 3" minimum vent through the roof rule separately to the addition and the existing building. I don't think there'd be any reason to treat them separately even in the former case, as the spaces are attached, but I'm not sure. If they were separate buildings, then I think the 3" minimum vent through the roof would apply to each of them separately.

Certainly you can route your lav vent through the ceiling framing/attic to exit the roof at a more favorable location.


It's not great, but it's OK, and it's no worse than the combo and the extra vent. I'm not sure if my latest drawing fits, but it avoids the net U-turn.

Cheers, Wayne
Hi Wayne, you mentioned a drawing. I didn't see a drawing attached.

The addition is attached, however, the two plumbing segments don't connect except at the same sewer drain about 10' outside the building footprint.
 
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