Shower drain into laundry sink

[jaywalker]

I am replacing tub with a standing shower.

On the adjacent wall is the laundry room. Where I have a laundry with 2" drain and 1.5" vent.

I wonder if I can drain the shower(not a tub) into the laundry drain(the laundry drain acting as a wet vent). Now I understand that the laundry has to be downstream of any other drain. Is that because of suds? Is that a problem for utility sinks?
I have been debating this configuration. If there is no risk for this configuration, can I use a San tee for the connection between sink, shower drain and waste.


My other option is to connect to the 1.5" drain coming from the lav. My concern here it is that it's 1.5". While 1.5" is ok for a tub but it may not be ok for standing shower(we are installing a curbless pan). I live in California so all fixtures are low flow fixtures.
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[Reach4]

I think vertical wet venting may do what you want. It looks like the line below the laundry tub trap would need to be at least 2 inches.

UPC 908.1 Vertical Wet Venting

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[wwhitney]

The configuration in the diagram does not conform with the UPC's requirements on vertical wet venting. UPC 908.1.1 requires the wet vented section to be at least one size larger than the minimum drain size for the drainage carried, and at least one size larger than the minimum vent size for the fixtures wet vented. The minimum drain size (after vent takeoff) for a laundry sink is 2", so the wet vented section would need to be larger than 2".

Chapter 9 Vents: Vents, California Plumbing Code 2022 | UpCodes

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But you could take a dry vent off the shower trap arm before it joins the laundry sink, and bring it up vertically (at most 45 degrees from plumb) to join the existing 1.5" laundry sink dry vent at an elevation at least 6" above the laundry sink's flood rim (and the shower's, but the laundry sink's flood rim is higher).

The UPC requires a 2" shower drain, so utilizing the 1.5" lavatory drain is also not an option.

Cheers, Wayne

 

[jaywalker]

The configuration in the diagram does not conform with the UPC's requirements on vertical wet venting. UPC 908.1.1 requires the wet vented section to be at least one size larger than the minimum drain size for the drainage carried, and at least one size larger than the minimum vent size for the fixtures wet vented. The minimum drain size (after vent takeoff) for a laundry sink is 2", so the wet vented section would need to be larger than 2".

Chapter 9 Vents: Vents, California Plumbing Code 2022 | UpCodes

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

up.codes

But you could take a dry vent off the shower trap arm before it joins the laundry sink, and bring it up vertically (at most 45 degrees from plumb) to join the existing 1.5" laundry sink dry vent at an elevation at least 6" above the laundry sink's flood rim (and the shower's, but the laundry sink's flood rim is higher).

The UPC requires a 2" shower drain, so utilizing the 1.5" lavatory drain is also not an option.

Cheers, Wayne

Some additional context. My shower drain is a linear drain.

There is a 14" I-joist under the wall between laundry room and the bathroom. The existing laundry drain comes through the drywall section where it is vertically dry vented with a San Tee. The waste line then bends around the joist flange and goes about 9 inches down before it bends 45 inches vertically to go down the exterior wall.

Sounds like, I will need to branch off the vent from the shower trap arm, bring it through the joist webbing then up the floor through the vanity cabinet box and back into the interior wall(non load bearing) where it travels vertically before tie-ing at 6" above floor level into the existing dry vent.

 

[Reach4]

Sounds like, I will need to branch off the vent from the shower trap arm, bring it through the joist webbing then up the floor through the vanity cabinet box and back into the interior wall(non load bearing) where it travels vertically before tie-ing at 6" above floor level into the existing dry vent.

Shower vent will have to be within 45 degrees of plumb (vertical) until 6 inches higher than the shower flood level. Your words may have painted that picture to you, but I did not follow it.

"bring [the vent pipe] through the joist webbing then up the floor" sounded like it might involve something going more horizontal.

Also, if you join the dry vent to the shower arm, the wye would be pointing the opposite of way of your first sketch.