Why would more water get behind that once it's grouted than any other tile? Because it runs horizontally? But it has the slope in the back so water won't pool at the back on any grout lines. Doesn't make sense to do it any other way than the way the handyman has done it. I just googled and see some examples of it done the other way - it makes them look like after thoughts to me.

Okay, I am so glad I found this post!!! Here is our delimma. We built a new home two years ago in an area that has been building new homes during these two years all around our home. Over these two years we have experienced this 'dark water' through our pipes - toilets, sinks, kitchen. No ordor, and it goes away after 6 hours. It has remained on our 'punch list' with our builder and they have had plumbers out who drained our gas water heater, and these plumbing companies have no clue why this continues. You would think this is a common event somewhere and that they should say, "oh yes, that is.... All we need to do is....." But they have been clueless. We worry if it is from the inside of the house and we don't flush one of our toilets well enough upstairs, or wonder if the construction in the neighborhood has caused it. Our neighbor next door has had it one time when we had it so we think it is from the outside vs the inside. Hamster, I hate to tell you, but that may not be the problem. I would like to know if it comes back.

I understand the concerns about using dish soap if it tends to dry your hands. That hasn't been a probelm for me, but I do have a child with OCD who tends to wash more than necessary, so for a while I switched from the antibacterial dish soap to a dish soap that was not antibacterial. It was gentler on the hands, and kept my child's hands from cracking (and sometimes bleeding) as they had with the antibacterial soap. Since then, I've diverted my child from constant hand washing to using hand sanitizer in between a normal amount of hand washing, which has solved the problem. Now I can use whatever kind of dish soap I want. But if it doesn't bother your hands, dish soap is a perfectly good hand soap. (My grandmother even used dish soap for shampoo, which I do occasionally for a super cleansing of all hair products from my hair, with no discernible harm.)

Thanks to everyone for all the comments. I truly believe that I have clogged roof vents. Won't know for sure until I get someone to snake them and see if it takes care of the problem. The plumber that just came out told me that he thinks I have a cracked/broken pipe and that he would return when his camera is working so he can scope it out. I honestly do not believe that I do and I'll find out if my theory is correct once I've had the vents cleared. I will only pay for him to "diagnose" as a last resort. From what I've learned doing research and speaking to people with the same issue, the most probable cause is a clog. Also, the plumber did change the wax seal but that didn't stop the water from coming up. Will be replacing it again when my issue is resolved cause water has been coming up through that wax seal. I'll definitely update when I resolve issue. Hope my experience can help someone else.