Kitchen Sink Rough In - Below Flood Rim

[Paul E.]

I am working on my kitchen plumbing rough in. There is a steel beam overhead of the kitchen sink, so my vent line will have to turn a corner, as shown below. I will replace the sanitary tee I used in the mock-up with a 2” x 1-1/2” x 1-1/2” so I can eliminate the bushing.

Is there anything I am doing wrong with this setup?

 

[Breplum]

2" cleanout is required, so good...you don't want to drill out that supporting so-called post/studs, so maybe two 45s to make the turn without cuts.

 

[Sponsor]

 

[wwhitney]

As per the title of the thread, the horizontal portion of the vent needs to be at least 6" above the sink flood rim.

 

[Paul E.]

As per the title of the thread, the horizontal portion of the vent needs to be at least 6" above the sink flood rim.

I believe UPC will allow the vent to run horizontally until I am clear of the steel beam overhead.

Unless prevented by structure, the vent rises vertically 6 inches above the floor level rim before continuing to horizontal. Vent pipe located below flood level of rim is drainage pattern. UPC 905.3

 

[wwhitney]

I believe UPC will allow the vent to run horizontally until I am clear of the steel beam overhead.

You obviously have other routing options that will not require running horizontally below the flood rim level, so I would say the exception does not apply.

Cheers, Wayne

 

[Reach4]

A picture marked up to illustrate the 45 degree for the vent. 45 is considered vertical for this purpose.

Easier would be to have the santee off to the left, and bring a horizontal line from the trap adapter under the window to the side of the santee.

Then route the waste from above to join somewhere after the santee, I think. So no diagonal pipes thru studs that way.

 

[Paul E.]

You obviously have other routing options that will not require running horizontally below the flood rim level, so I would say the exception does not apply.

Cheers, Wayne

Hey Wayne, what other routing options do you see? My half wall (plumbing wall) is centered on the steel beam above, so I’m not sure how else it could be routed without popping a vent through the countertop.

 

[wwhitney]

A simple option, not necessarily the best, is below. Blue is 2" drain, Red is 1-1/2" trap arm, and Green is 1-1/2" vent. The trap arm is limited to 42" by the UPC, so if the distance drawn is greater than that, the san-tee could move to the left, with the vent turning 45 to the right at a lower level.

Wrapping the green vent around the inside corner while minimizing intrusion into the cabinetry might be tricky but is feasible. Turning the vent 90 degrees in plan (projected onto the floor) while the vent is 45 degrees from plumb before and after the turn requires a 60 degree elbow. In the markup below my attempt to show that appears as a very shallow kink in the diagonal green line.

Cheers, Wayne

 

[Paul E.]

Thank you for taking the time to sketch that Wayne! That’s very helpful.

For my own education, between the two options, if we pretend the first one was granted an exception and allowed, is there a difference in performance between the two? Is there any benefit to having less pipe and shorter travel distances for waste from the sink?

 

[wwhitney]

Beyond my experience to say.

Obviously the two extra elbows in the drain path is some detriment. Depending on the distance left-right, you might be able to do the drain offset with only 45s, not 90s. The san-tee can be farther to the left, with a street 45 on top, that would reduce the drain offset.

Also, depending on what type of sink you have and what's connected, i.e. one or two basins, garbage disposal, dishwasher, the trap arm stub out may not want to be centered, and could be at a 45.

Cheers, Wayne

P.S. If you came out of the slab with an immediate 45 to the upper right (before the cleanout), and if that would let you hit the upper right corner of your knee wall, so that the vent could wrap around the post as required, and if the kitchen sink stub-out could be to the right side of that diagonal run, then you can do the kneewall plumbing with just that 45, a wye for the trap arm coming in, and a LT90 for the trap arm to stub out. Just an FYI; I don't see any way to make that work with the stub-out where you have it.

 

[Daniel Collick]

Thank you for taking the time to sketch that Wayne! That’s very helpful.

For my own education, between the two options, if we pretend the first one was granted an exception and allowed, is there a difference in performance between the two? Is there any benefit to having less pipe and shorter travel distances for waste from the sink?

JMO, but my preference would be to simplify the waste as you have done. Running vents below a flood-rim is not uncommon especially in similarly scenarios, just grade the horizontal portions and use long turns where it’s appropriate. The intent is so the portion of the vent that’s below flood-rim drains in case it ever backs up. Just don’t tie any vents from other fixtures together until they’re above the flood-rim. Inspectors in our area would approve your rough-in. Again, JMO.