How to fix this sink drain leak

[Steve7878]

Have a kitchen sink drain and small leak at the last L where it comes out the wall. The line in the wall is 1-1/4” copper and runs about 3 ft horizontal to the vent stack. Built about 1950.

Drain line in the crawl space has already had the copper drain replaced with 1 -1/2” PVC

Plan A was to cut open the back of 2 cabinets to replace that 3 ft section with pvc to the vent stack. Guess would have to piece together a few short pieces to fit in between the studs.

Plan B may be less work. And l would lower the drain a little so could add a garbage disposal. The line going in the wall now was a little too high to install one before.

But with this plan I would just cut open the sink cabinet back. And have a Tee. The top of the tee would tie into the old copper line for a vent.

Then drill a 1-1/2” hole thru the bottom wall plate. Then connect the bottom of the tee to the pvc drain line in the crawl space.



Is there any problem with either plan?

Thanks for any suggestions.

 

[Reach4]

Is this under a window?
Where does the water leakage appear-- where the drain line comes out of the wall, or elsewhere?

 

[Sponsor]

 

[Steve7878]

Yes, under a window. Right now leak is just at the first elbow in the wall. But have a few neighbors with same type house, that have had the same problem in the past year.
So makes me believe it is just past its life span, and I am worried about hidden leaks in the wall.

 

[Reach4]

I agree with your diagnosis and plan A. I think plan B would not be permitted, since it involves a dry vent going horizontal lower than 6 inches above the flood level of the sink.

An AAV would be an alternative, and then use a new drain line thru the floor. But you would still need to continue the old vent down to drain out rain and condensation in the existing vent, or you would need to block that off in the attic I think. I am not a pro.

 

[Steve7878]

I agree with your diagnosis and plan A. I think plan B would not be permitted, since it involves a dry vent going horizontal lower than 6 inches above the flood level of the sink.

An AAV would be an alternative, and then use a new drain line thru the floor. But you would still need to continue the old vent down to drain out rain and condensation in the existing vent, or you would need to block that off in the attic I think. I am not a pro.

Yes, would leave the alone. It already goes into the crawl space and attaches to the sewer line.