So I've been fighting an in-wall leak that I just can't seem to remedy ... all the rain we've been getting here in N. Carolina hasn't helped the situation either.
Anyway, this particular pesky leak is in an interior wall that separates the bathroom from the bedroom (see arrow in floorplan pic). It all started after I found the the floor under the sink wet during a random inspection. It's led to me removing the fixed bedroom "nightstand" cabinet, the fixed bathroom vanity, and the wall covering on the bathroom side ... all in an attempt to track down the source.
First, I found a staple that had punctured a supply line feeding the bathroom sink ... occurred during assembly ... replacing that supply line required me to remove the fixed bedroom "nightstand" cabinet. Thought I had it licked after ... but, no.
Second, I found that the plastic in-wall check valve for the black tank washer had a leaky/loose fitting. To get to that, I had to remove the fixed bathroom vanity, and the wall covering on the bathroom side. While exposed, I took the opportunity to upgrade the valve to brass vs. the plastic version. Thought I had it licked again ... but, no.
I've been watching the area while everything is still out. The base of the wall is still getting wet. Absolutely no evidence of water higher than the base of this wall, nor anywhere else on the floor around it.
What I've found now is a dry ABS pipe joint (see pic) - this is the drain for the bathroom sink & "also" extends on up to the roof vent. The sink is not even installed, so no water has been going down this pipe since the last dry-out. They glued every single joint, but missed this one (thanks Thor) - as a low pressure pipe, I'm not sure if its a contributor - but, I'll probably go through the frustration of cutting it all out & getting it glued in anyway.
On the vent cover (roof), I also found a screw that didn't quite have Dicor completely covering it. I'd say that was the culprit (water running down the vent pipe); but, I see no evidence of such at all. I'll get it all sealed up proper nonetheless.
Other than all that, I'm starting to be at a complete loss as to why the base of this little wall keeps getting wet. Any ideas anyone? The water damage to the surrounding wood (some MDF) is starting to take its toll, so I need to get it fixed soon.