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 Kitchen drain replacement PART II
Author: sum (FL)

Last month I cut open the concrete slab to repair my kitchen drain. This is the link to that discussion:


The drain in question is a 2" cast iron drain located right under a common wall between two apartments. Apartment A is to the north and has a kitchen island (renovated in 2008) and apartment B is to the south and has a traditional kitchen.

Turned out there are a whole bunch of problems. The 2" cast iron drain is badly corroded and a section of it was totally rotted out at the bottom. The new PVC section from kitchen island in apartment A has an inverted slope (running uphill), plus it has a "dog leg" elbow with a p-trap (with a slip joint) under the slab, then another p-trap above the slab inside the sink cabinet. I have since enlarged the slab cut opening in apartment B, as well as made a cut under the island in apartment A.

Then I used a tunnel jet kit under the slab for a 3/4" pipe, then I increased it to 1", then 1.5" and finally I was able to run a 2" pipe at 1/4" per foot slope to the island. This is what I have done so far.

In apartment A this is the slab cut, the kitchen island has been moved out of the way. The 2" pipe starts here and runs south.

Further south is the kitchen common wall, and now you are looking at the other side of the wall in apartment B. See the existing CI pipe that has been cut back, and connected to a 2" combo fitting coming from the 2" pipe from the island.

I have not yet completed the section on the left that runs to the drain/vent for apartment B. I'll get to that later on this week.

Here is a sketch of the top view. The brown line is existing CI. The red line is new PVC.

The question I have is is the island drain properly wet vented? The distance from the island to the combo is less than 7'. The distance from the vent/drain to the combo is less than 4'.

Do I need a studor vent inside the island sink cabinet on the outlet side of the p-trap?

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 Re: Kitchen drain replacement PART II
Author: sum (FL)

This is part of what I took apart.

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 Re: Kitchen drain replacement PART II
Author: steve (CA)

Sum, you need to install an AAV. The sink trap needs to be above the slab, so you would be creating an S-trap if there was no AAV.

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 Re: Kitchen drain replacement PART II
Author: stuckinlodi (MO)

I think I would have considered moving to another place. What a lot of work!

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 Re: Kitchen drain replacement PART II
Author: sum (FL)

steve, yes I have forgotten about the S-trap. AAV it is.

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 Re: Kitchen drain replacement PART II
Author: exapprentice30 (MA)

Keep the aav as high as you can.You can offset with a couple of 45 s if you need. You can add a clean out tee for future use too.

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