Basement Bathroom Wet Vent + AAV

[kevinwatson]

DIY plumbing a basement bathroom in Michigan (IPC) and am wondering about venting. Only real access to existing stack is a 3" line that carries waste from other bathrooms on other floors so I believe that is a no-no. I've got a revised plan drawn out and attached. I can use an AAV in my location but I'm wondering if the rest is good? I've bumped up the lav and shower/tub to 2" for the wet vent purposes. Thanks for the help!

 

[Jeff H Young]

Connect main drain downstream of w/c connection also why not 1 1/2 trap arm for the lav?

 

[Sponsor]

 

[Tuttles Revenge]

Only fixtures that are part of the bathroom group may drain through the horizontal wet vent system. The toilet needs to be wye'd off of the horizontal wet vented portion and only 1 fixture can be upstream of the dry vented fixture. So it would need to be downstream of the sink drain.

Chapter 9 Vents: Vents, 2018 Michigan Plumbing Code | UpCodes

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912.1 Horizontal Wet Vent Permitted
912.2.1 Horizontal Wet Vent

Looks like AAV are permitted but may have to read some of the fine print.. which I haven't in a while.

Chapter 9 Vents: Vents, Michigan Plumbing Code 2015 | UpCodes

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[Jeff H Young]

bringing the main drain to downstream of w/c would sovl

Only fixtures that are part of the bathroom group may drain through the horizontal wet vent system. The toilet needs to be wye'd off of the horizontal wet vented portion and only 1 fixture can be upstream of the dry vented fixture. So it would need to be downstream of the sink drain.

Chapter 9 Vents: Vents, 2018 Michigan Plumbing Code | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

912.1 Horizontal Wet Vent Permitted
912.2.1 Horizontal Wet Vent

Looks like AAV are permitted but may have to read some of the fine print.. which I haven't in a while.

Chapter 9 Vents: Vents, Michigan Plumbing Code 2015 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Dosent tieing the main in down stream of the toilet solve all issues? there is only one wet vented fixture upstream of the dry vent that I see

 

[John Gayewski]

Looks to me if he just changed the 4x2 wye to a 4x3 wye and piped the toilet off of that he'd be good.

Also yes, the lav trap arm should be 1.5"

 

[Jeff H Young]

yep no other issue main drain seperated from wet vent good to go!

 

[kevinwatson]

@Jeff H Young @John Gayewski Thank you for the quick responses. Would this revised layout work?

 

[Tuttles Revenge]

bringing the main drain to downstream of w/c would sovl

Dosent tieing the main in down stream of the toilet solve all issues? there is only one wet vented fixture upstream of the dry vent that I see

Same thing I think. just different ways of saying it. I think we were answering at the same time initially. I was just rushing out the door to meet my guys starting a new project

 

[kevinwatson]

yep no other issue main drain seperated from wet vent good to go!

Thanks for the help. I think I'm understanding correctly. Do a 4x3x3 wye off the main, do a wye for the toilet, a wye for the vent/lav, and 2" for the tub/shower? Or would the toilet need to tie-in before the vent goes up?

 

[Tuttles Revenge]

Thanks for the help. I think I'm understanding correctly. Do a 4x3x3 wye off the main, do a wye for the toilet, a wye for the vent/lav, and 2" for the tub/shower? Or would the toilet need to tie-in before the vent goes up?

@Jeff H Young @John Gayewski Thank you for the quick responses. Would this revised layout work?

Almost there. I believe that All connections to the horizontal wet vented system must be made with horizontal connections, So the sink WYE should be horizontal then 90 up.. One fixture, your tub/shower may be upstream of that dry vented fixture.

**EDIT**
This is where my understanding the horizontal connection comes from. I don't plumb in IPC so I'm not as steeped in it as UPC.

912.2.1 Horizontal Wet Vent​

The dry-vent connection for a horizontal wet-vent system shall be an individual vent or a common vent for any bathroom group fixture, except an emergency floor drain. Where the dry-vent connects to a water closet fixture drain, the drain shall connect horizontally to the horizontal wet-vent system. Not more than one wet-vented fixture drain shall discharge upstream of the dry-vented fixture drain connection.

 

[wwhitney]

Almost there. I believe that All connections to the horizontal wet vented system must be made with horizontal connections,

This is a confusing point of disagreement between the IRC and IPC (although for the configuration shown in post #7 it turns out not to matter). The IRC's plumbing section has language similar to what you mention, but the IPC does not. In jurisdictions that adopt both the IPC and the IRC's plumbing sections, what often matters for single family residences is the language in Chapter 1 of each code, which clarifies whether the plumbing must be done per the IRC or whether the option to use the IPC is available.

For the OP, MI has adopted both the IPC (based on 2021 IPC) and the IRC (based on 2015 IRC), and the Chapter 1 language specifies that the IRC is operative for single family residences, with no option to use the IPC.

So the relevant section of the IRC is P3108.1, which states:

" . . . Each fixture drain shall connect horizontally to the horizontal branch being wet vented or shall have a dry vent."

Chapter 31 Vents: Vents, Michigan Residential Code 2015 | UpCodes

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up.codes

That language requires the tub/shower and the WC to connect horizontally to the wet vented horizontal branch. However, I would say that the lavatory is exempt from that requirement, as it does have a dry vent.

Thus I see no issue with the configuration show in post #7, looks IRC compliant to me.

Cheers, Wayne

 

[kevinwatson]

This is a confusing point of disagreement between the IRC and IPC (although for the configuration shown in post #7 it turns out not to matter). The IRC's plumbing section has language similar to what you mention, but the IPC does not. In jurisdictions that adopt both the IPC and the IRC's plumbing sections, what often matters for single family residences is the language in Chapter 1 of each code, which clarifies whether the plumbing must be done per the IRC or whether the option to use the IPC is available.

For the OP, MI has adopted both the IPC (based on 2021 IPC) and the IRC (based on 2015 IRC), and the Chapter 1 language specifies that the IRC is operative for single family residences, with no option to use the IPC.

So the relevant section of the IRC is P3108.1, which states:

" . . . Each fixture drain shall connect horizontally to the horizontal branch being wet vented or shall have a dry vent."

Chapter 31 Vents: Vents, Michigan Residential Code 2015 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

That language requires the tub/shower and the WC to connect horizontally to the wet vented horizontal branch. However, I would say that the lavatory is exempt from that requirement, as it does have a dry vent.

Thus I see no issue with the configuration show in post #7, looks IRC compliant to me.

Cheers, Wayne

Much appreciated!

 

[Jeff H Young]

Almost there. I believe that All connections to the horizontal wet vented system must be made with horizontal connections, So the sink WYE should be horizontal then 90 up.. One fixture, your tub/shower may be upstream of that dry vented fixture.

**EDIT**
This is where my understanding the horizontal connection comes from. I don't plumb in IPC so I'm not as steeped in it as UPC.

912.2.1 Horizontal Wet Vent​

The dry-vent connection for a horizontal wet-vent system shall be an individual vent or a common vent for any bathroom group fixture, except an emergency floor drain. Where the dry-vent connects to a water closet fixture drain, the drain shall connect horizontally to the horizontal wet-vent system. Not more than one wet-vented fixture drain shall discharge upstream of the dry-vented fixture drain connection.

Good eye Tuttles , Yea Im still trying to get this only place I ve learned about horrizontal wet venting is on the forum and the codes online I never did any of this venting on commercial work and got out of most home building in 03, little jobs remodel etc Ive stuck to old way for most part think ill remember this tip though on entering the wet vent on the horrizontal