Got a whole ‘nuther scenario for you. We live in a slab house built in the late 50’s. After living here nearly 10 years, a couple of years ago we started noticing an area in the middle of the kitchen floor was getting and staying awfully warm- hot actually. Then we noticed when we would first turn on the cold water in the kitchen sink, it would come out pretty darn hot at first, then become cool like it normally was. Hot water worked same as ever.
My wife, who has a lot of sinus problems, started complaining of getting unusually stuffed up. Around that time we got a notification from the water company that they suspected we had a leak.
Putting two or three together and dividing by five, I deduced that the hot water line, buried under the slab, had at least partially ruptured under the kitchen floor between the water heater and the kitchen sink. This hot water pooled around the cold water line, heating it up, thus it would come out hot at first, then the fresh cold water coming thru that hadn’t had time to get hot yet, would flow thru and come out cool.
We rerouted the lines from the heater to the sink. No leaks, normal temperature floor, normal temperature water out of the spigots, and after a few months of the ground drying, my wife’s allergies were back to normal levels.
