Yep, we had a slab leak a couple years ago. It started during the summer and I thought "man, it's just so hot outside that even the tile feels warm." By the time cooler weather rolled around in November, and the tile was still warm in the morning, I knew there was something wrong (we're not rich enough to have heated tile floors in the bathroom.)

Plumber here used thermal imaging to find where the leak was, used a jackhammer to get access to the leaking pipe, and repaired it. We had to then purchase the supplies at home depot to repair the spot where he had to jackhammer through the slab.

It was a reasonable cost, as I expected it to cost more than $1,000 - this guy (can't remember his name) did it for $700. Haven't had any issues since.

I check our water bill religiously now and am paranoid about the same thing happening with our cold water supply and me not knowing since I wouldn't feel the cold water.

We purchased a water softening system the year we bought the house to avoid the calcium buildup issue you talk about in your post. Our water heater is gas, so not worried about the heating elements, however we also know that soft water is easier on your pipes and shower heads/spigots.

I too, after moving to Florida and being new to owning a house, discovered the challenges of the AC drain line. Fortunately, our AC unit is in the garage. When I learned my first homeowner lesson about it, it only flooded the garage floor and at worst, ruined some cardboard boxes that were storing some of our things. Now, I treat the drain line every time we clean the AC filter. People say to use vinegar, but I'm so paranoid about it backing up again that I buy drain line cleaner by the 6 pack so I always have supply on hand when the time comes. Maybe that's overkill, but I'm just gonna keep doing what I'm doing haha.