Possible for Water Lines to Cross 4" Vent in a 2x4(.5) Wall?

[clw143]

I have a 4" PVC pipe coming out of the slab and going up through my roof, this is a single story with a septic if that matters. The issue is that hot water is to the right of the main stack, and cold to the left. The wall was spaced on one side of the studs with 1/2 plywood to give enough room for the 4"pipe and there is absolutely no way to go around it. I need to have both (hot and cold) on both sides of the vent. The only way I see doing it is to reduce it down and right back up to 4". I found where Louisiana Code says "Such vent shall run undiminished in size..."

Are there any exemptions to this where I can reduce and return to 4"?

If I can not reduce it, can I take a heat gun to it and flatten it out a bit oval like to get by it?

 

[wwhitney]

A 2x4 is 3.5" deep, and a 4" Schedule 40 pipe is 4.5" OD, so you'd need add 1" of furring, or else gouge out the back of the drywall. And hubs are at least an extra 0.5" in diameter, so you really need a 2x6 wall to contain 4" fittings.

But unless your house is really large, you're unlikely to need any 4" DWV anywhere inside the house. You could figure out how to put a 4" cleanout just above the slab, and run only 3" above that, including the vents.

As to your question, no squashing of the pipe. If you have a perpendicular adjoining wall running into your plumbing wall near the stack, and if you have room for DWV fittings within the plumbing wall, you could do something tricky like jog the stack from one side of the adjoining wall to the other, and then back again. That would let water supplies cross over the stack by going into the adjoining wall and then rising or falling within the adjoining wall. Effectively using the adjoining wall as a "bump out" for passing over the stack.

Cheers, Wayne

 

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[Reach4]

I have a 4" PVC pipe coming out of the slab and going up through my roof, this is a single story with a septic if that matters. The issue is that hot water is to the right of the main stack, and cold to the left. The wall was spaced on one side of the studs with 1/2 plywood to give enough room for the 4"pipe and there is absolutely no way to go around it. I need to have both (hot and cold) on both sides of the vent. The only way I see doing it is to reduce it down and right back up to 4". I found where Louisiana Code says "Such vent shall run undiminished in size..."

Are there any exemptions to this where I can reduce and return to 4"?

If I can not reduce it, can I take a heat gun to it and flatten it out a bit oval like to get by it?

Is this in a bathroom interior wall, and you only need to supply the lavatory and tub with hot? Is this a kitchen on an exterior wall and you need to supply cold to the sink?

Do you know what is below the floor?

 

[clw143]

Is this in a bathroom interior wall, and you only need to supply the lavatory and tub with hot? Is this a kitchen on an exterior wall and you need to supply cold to the sink?

Do you know what is below the floor?

The vertical 4" vent is in an interior wall. I need hot and cold on both sides of the vent, left of the vent would be a shower and tub, right of the vent would be Vanity.

The house is on a slab, below it is dirt.

 

[Reach4]

Can you put crossovers inside of a vanity or kitchen cabinet? If not, you could build a soffit around the crossovers.

 

[clw143]

You could figure out how to put a 4" cleanout just above the slab, and run only 3" above that, including the vents.

I see where code references doing it for trailers, does IPC code allow this, I don't see it.

 

[wwhitney]

I see where code references doing it for trailers, does IPC code allow this, I don't see it.

The IPC will only require a 3" building drain for many (most?) houses; if you get enough WCs or enough DFU total, it will require a 4" building drain.

If you have a 4" building drain under the slab, but 3" suffices to meet the IPC requirements, you can just run 3" for everything above the slab, and convert to 4" as you enter the slab. This is unrestricted as you are increasing the drain size in the direction of flow.

What is the current state of construction, is the slab already poured? If not, and the drains under the slab aren't installed yet, and a 3" building drain suffices, you don't need to install any 4" under the slab. I think it is common to switch to 4" where you exit the building; that's the point where the building drain becomes the building sewer, and using a 4" minimum sewer is common. [Sewer basically means "sanitary drain outside the footprint of the building."]

Cheers, Wayne

 

[clw143]

What is the current state of construction, is the slab already poured?

Yes. House was built in the late 70's. That all makes a lot of sense. Thanks for the input.