I have a two-story townhouse condo built on a slab. The first-floor forced-air ducts run under the slab. The runs are 8" PVC pipes but the turns are actually round sheet metal. They were not made water tight. In times of heavy rain, ground water seeps into the ducts. I have attempted to seal the joints I could reach but there is one joint around a corner that I cannot reach.
I took a picture with my phone but can not upload it or post a link to my Dropbox. I cannot yet prove that the water is coming from around the bend. When the level drops, I should be able to dry it and then watch where it comes in from.
Does anyone have any suggestions how I can seal that joint? I would really (REALLY) like to avoid jackhammering through the slab.