My wife & I renovated our master shower a couple years ago. About three months ago, we noticed the baseboards in the guest bathroom (on the other side of the wall from the master bath) were getting water damage (similar to how they were getting damaged a couple years ago, thus the shower remodel). I tore out the baseboards & sure enough, water was showing up just like it did a couple years ago. I called my contractor friend out to look (he had spear-headed the original remodel) & his thoughts were that it wasn't leaking thru the tile/hot-mop since none of our tiles were displaced or coming off. So I tested - I plugged the drain & filled the shower with water. It held water for 6-8 hours without any showing up in the guest bathroom, but as soon as I took a shower, there was the water! This made me think it was the drain under our slab, but how was the water getting up?
Here is what I think is happening, but I would like some thoughts on how to remedy it without tearing up my newly-remodeled shower. I think the Fernco adapter mating the original cast iron pipe with the new PVC pipe is leaking. Of all of the pictures I took during the remodel, one of them showed the plumber didn't clean up the cast iron pipe before attaching the Fernco adapter. I believe this joint is leaking, the soil around this joint is now saturated and the water is being forced up thru the slab at the point where the vent pipe goes thru the slab. I called a company that does pipe relining, but they wanted $1800 for this three foot run and wouldn't guarantee a seal since they were getting to the problem area thru the shower trap. I do need to get a couple more estimates, but at this price it might just be cheaper to tear up the shower floor & fix it correctly, thereby confirming the problem & guaranteeing a fix.
Does anyone have any other ideas as to how to fix it? I'd appreciate any thoughts.