Most of my family lived for decades on slab homes in FLA. Not one ever had a problem with the plumbing under the slab. My parents only had one basement home. Every other home has been a slab. Our city house in NC was a slab home built around 1975. No problems with the plumbing.
Personally, I HATE crawl spaces and the idea of having a toilet on wood makes me shudder. One morning, our toilet over flowed in our city slab house. To make it worse, the danged toilet kept running so it dumped more water on the floor. :shocked:
Did I mention I was late to a closing? The closing on our loan to build our current house? :shocked: After I stopped the toilet, and sorta clean up the mess, the wifey had to deal with most of the water, I went the lawyers office. The closing was a disaster but that is another story. Luckily, the slab was unlevel from the bathroom to the laundry room so the water stayed on vinyl flooring and did not get to the carpet. It would have been worse if we had been on a crawl space or basement. A coworker bought a fairly new house with a crawl space and had to completely redo the bathroom floor because the toilet had leaked and rotted out the subflooring. The floor, including the tile, had to be ripped up and replaced.
When we built our country house we put in a slab. Most people would have put in a crawl space, and given that we have a decent elevation change, so that one side of the house is about 18 inches above grade and the other is about 60 inches, a crawl space would have been a what most people would have done. Instead of a crawl space, the foundation was filled with 67 stone and then a slab was poured over rigid insulation. The PVC is was installed, sealed and pressurized before the gravel was put into place. 67 stone compacts as it is laid and does not settle. The pressure gauges showed no leakage and eventually the slab was poured. No problems in 10 years.
A neighbor has a crawl space and I don't know if they have fixed their messy crawl space. I looked into the crawl space when the house was mostly finished and about to be foreclosed. Long story there. Anyway, the house was maybe 6-9 months hold and the crawlspace was full of moisture and multi colored mold. :shocked: Now that ain't normal in a crawlspace but it is the sort of problems/nightmare one can get. Now a days, I would build a crawlspace that was sealed if I had to have a crawlspace.
A crawlspace to me is a negative, not a positive in a house.
Later,
Dan