About a year ago, our old washing machine had a water-level sensor failure, and it overflowed (for about 15 minutes before we noticed). It's on the third floor of our home, and luckily (by code) is in an overflow pan and connected to a drain pipe that runs out of the house, so most of the water didn't cause any damage.
Unfortunately, the way that my wife and I did notice was that water started dripping from the ceiling of our 2nd floor living room ceiling (not quite directly under the laundry room, but obviously on the path of the drain pipe). It wasn't a tremendous amount of water, but enough to cause a stain on the ceiling.
We ended up replacing the washer and obviously wouldn't expect to have a similar overflow issue again... but now I'm wary of having a known issue with the drain pipe (particularly when it comes to selling the house down the road) - although I don't really want to cut up the whole 2nd floor ceiling or 3rd level floor to try and get to the pipe and fix it.
Given all of this, is there anything (magic mystery oil, perhaps) that can be poured into a non-pressurized drain pipe such as this (maybe followed by water to wash most of it out) that could coat the inside of the PVC pipe and seal what is likely a very small leak/loose PVC joint? I realize that this may sound like a ridiculous question, but given the situation, I'm open to any suggestions.