Help with diagnosing leak behind kitchen cabinet, leaking through stucco

[Jouster]

Hi everyone. Last night, Friday October 21st I noticed we had a plugged up sink and a small leak under the sink. The rubber of the Anti-vibration tailpipe piece into the garbage disposal was ripped. So I ordered a new piece coming tomorrow to fix that problem, and adjusted under the sink so I could at least use the left side of our sink and put a plug on the insinkerator dish rack side.

But today I noticed when taking out some trash that below our kitchen window, the stucco is all wet, and even had a small puddle under it as well. I've attached a few pictures. I apologize as it's already night time and I just barely noticed. Seems like an ABS pipe leak. As I don't have any expertise or experience with this, could I drill a hole in the stucco and take a look, or is it better to go through the wall under the sink? Or just any ideas at all will be super helpful, thank you!

-Respectfully,
Jonathan Feliciano

 

[Jeff H Young]

Pretty basic if you didn't have a leak under sink then its in the wall.
If your stucco is in perfect shape and the drywall is all beat up behind cabinet then I wouldn't bash out stucco. or vice versa.
You would know better if you have a leak or not. Perhaps if you didn't have a stoppage under normal use it wouldn't leak, but the stoppage isn't really a reason for it to leak inside the wall.
Assuming you can see through all the stuff under sink and you are sure its not leaking under sink

 

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[Jouster]

@Jeff H Young Thanks for your reply. After doing some research on the home, I found out that it was built in 1986 and probably a clay waste pipe that's leaking. I don't think I can comfortably work from under the sink to get to that pipe and replace it was ABS. The stucco was there from 1986 so the hard part is it wont match when fixed up, and I don't know if there is a steel beam, how thick and where is the best way to go at this.

 

[Weekend Handyman]

I am not a pro. I would 100% go through the interior wall. Much easier and cheaper to fix drywall. No stucco to speak of in my area, but I am pretty sure it is applied to metal lath, which I am sure is a joy to cut through.

 

[Jeff H Young]

Pictures weren't very good but if reachable from under cabinet a dry wall patch and isn't that hard nor need to be perfect.
1986 single family home in Los Angeles county about 99 percent chance ABS it wouldn't be clay . claypipe for sewer after exiting home a foot or so outside very unusual too unless its right on the property line we never run clay to the house in the 80s.
since the pics weren't worth 1000 words I'd say just make hole in drywall if worse case scenario you have a patch under the sink

 

[Jouster]

@Jeff H Young @Weekend Handyman Thanks for your input. Jeff you are correct it is ABS. The only problem is everything is dry that I can see and reach. I think the leak is to the right and I can't get to it. I'm not sure if the pipe has an elbow and goes down to the first floor. I need a camera to see where it is I guess. I live on the second floor of the house we own which is a duplex. I'm sure the ABS pipes are glued and don't see how I could replace it and fix it without doing it from the outside of the house unfortunately. This is how it looks right now:

 

[Weekend Handyman]

I might let it dry out, hook you sink back up, and let the water run to see what happens. If you get water again, you will know it is the plumbing. If there is no water where you have open, you will know it is down further. If you do not get any water where it should not be, it might not be the plumbing.

If you have had rain lately, I wonder about how well your security light is sealed. Water could be entering there and going down the wall. It could also be from the window, but I feel that is less likely given it is pretty close to the roof overhang.

I also wonder (again I know nothing about stucco) if there should be a drip edge at the bottom of the stucco. If not and if you have had rain, the water could be coming down the wall, and absorbing into the underside. Here is a video of Tom Silva talking about drip edge: