Independently vented washer feeding into a horizontal wet vent

[Gmandesigns]

Hello all, I'm having trouble deciphering chapter 9 of the IPC with regard to horizontal venting. I have a washer with its own vent that discharges into a 3" horizontal section. I want to add a dry vent to that 3" line so that it is between the washer and a bathtub/shower. My question is whether I can use a short distance of the horizontal 3" pipe as a vent for the shower? The washer and shower are on the same level. Thank you for any responses!

 

[John Gayewski]

Hello all, I'm having trouble deciphering chapter 9 of the IPC with regard to horizontal venting. I have a washer with its own vent that discharges into a 3" horizontal section. I want to add a dry vent to that 3" line so that it is between the washer and a bathtub/shower. My question is whether I can use a short distance of the horizontal 3" pipe as a vent for the shower? The washer and shower are on the same level. Thank you for any responses!

View attachment 84644

As far as I know ipc won't let you do that and neither will upc. Horizontal wet venting is for bathroom group fixtures only.

 

[Sponsor]

 

[Gmandesigns]

As far as I know ipc won't let you do that and neither will upc. Horizontal wet venting is for bathroom group fixtures only.

I'm with you, but the washer is not technically wet vented. It just happens to be upstream of a horizontal vent section. Also, the ICC guide for Methods of Venting Plumbing Fixtures and Traps in the 2018 IPC states "The Circuit Venting method is similar to wet venting except that it allows you to combine a total of eight fixtures on a single floor that are not limited to the two bathroom groups". So maybe what I've created constitutes a circuit vent?

 

[Terry]

I'm not seeing washing machines listed for a circuit vent mixed with bathroom fixtures. Where did you see that?

 

[Gmandesigns]

I'm not seeing washing machines listed for a circuit vent mixed with bathroom fixtures. Where did you see that?

914.5 - "fixtures, other than circuit-vented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented." I cannot find anything that addresses washing machines specifically. Hence my confusion. Thank you!

 

[Terry]

Looking at their diagrams, it looks to be bathrooms. I'm UPC, but there should be some IPC plumbers that know that stuff here.

 

[wwhitney]

Here's TN's 2012 IPC section on circuit venting:

Chapter 9 Vents: Vents, Tennessee Plumbing Code 2012 | UpCodes

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

up.codes

The way 914 is written, specifically 914.2 and 914.5, the diagram would appear to me to comply if there were another shower on the horizontal drain, between the washing machine and the circuit vent. As then, if you delete the washing machine, it's a standard 2 fixture circuit vent; and 914.5 allows the separately vented washing machine to drain through the circuit vent, without any restriction of where it joins in (i.e. it doesn't say downstream of the circuit vent, for example).

Then given it would be OK with an extra shower, logically I would say it should be OK without the extra shower. The diagram is basically a 1 fixture circuit vent, with another separately vented fixture being used to wash the circuit vent. However, the way 914 is written, it doesn't seem to contemplate such an arrangement.

So while I would say that logically it should be allowed under IPC 914 Circuit Venting, I wouldn't be surprised if many inspectors/plans examiners didn't read IPC 914 that way.

Cheers, Wayne

 

[Gmandesigns]

Here's TN's 2012 IPC section on circuit venting:

Chapter 9 Vents: Vents, Tennessee Plumbing Code 2012 | UpCodes

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

up.codes

The way 914 is written, specifically 914.2 and 914.5, the diagram would appear to me to comply if there were another shower on the horizontal drain, between the washing machine and the circuit vent. As then, if you delete the washing machine, it's a standard 2 fixture circuit vent; and 914.5 allows the separately vented washing machine to drain through the circuit vent, without any restriction of where it joins in (i.e. it doesn't say downstream of the circuit vent, for example).

Then given it would be OK with an extra shower, logically I would say it should be OK without the extra shower. The diagram is basically a 1 fixture circuit vent, with another separately vented fixture being used to wash the circuit vent. However, the way 914 is written, it doesn't seem to contemplate such an arrangement.

So while I would say that logically it should be allowed under IPC 914 Circuit Venting, I wouldn't be surprised if many inspectors/plans examiners didn't read IPC 914 that way.

Cheers, Wayne

Awesome answer, thanks so much! My head was spinning on this one.

 

[John Gayewski]

I can say I've seen a washing machine drain act as a wet vent for a shower and it didn't work. Sudsing and water accumulation were two things that effected this setup. The way the drain was piped took 240° of turn at the shower wye which I don't think helped.

 

[Jeff H Young]

Here's TN's 2012 IPC section on circuit venting:

Chapter 9 Vents: Vents, Tennessee Plumbing Code 2012 | UpCodes

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

up.codes

The way 914 is written, specifically 914.2 and 914.5, the diagram would appear to me to comply if there were another shower on the horizontal drain, between the washing machine and the circuit vent. As then, if you delete the washing machine, it's a standard 2 fixture circuit vent; and 914.5 allows the separately vented washing machine to drain through the circuit vent, without any restriction of where it joins in (i.e. it doesn't say downstream of the circuit vent, for example).

Then given it would be OK with an extra shower, logically I would say it should be OK without the extra shower. The diagram is basically a 1 fixture circuit vent, with another separately vented fixture being used to wash the circuit vent. However, the way 914 is written, it doesn't seem to contemplate such an arrangement.

So while I would say that logically it should be allowed under IPC 914 Circuit Venting, I wouldn't be surprised if many inspectors/plans examiners didn't read IPC 914 that way.

Cheers, Wayne

Wayne, it also might not be classified as a circuit vent . in the definition the vent would serve 2 to 8 traps .

 

[wwhitney]

Wayne, it also might not be classified as a circuit vent . in the definition the vent would serve 2 to 8 traps .

I agree, that's the primary concern that I mentioned.

Cheers, Wayne