I have a home in N. Texas that was built in the 1950's. It sits on a slab foundation. The carpet in a hallway (interior, not close to an exterior wall) is constantly damp. The hallway is adjacent to 2 bathrooms, but is damp only near one of them. I have checked the water meter for a leak, but the dial does not spin (faucets, toilets, washing machine, dishwasher, etc. are all turned off when checking it.) This leads me to believe it's not a leak on the fresh water side, but rather on the sewage side of the plumbing. If this is the case, wouldn't the damp carpet smell badly? The bathroom closest to the damp carpet was not used for about a month to test and see if the carpet dried up, but it stayed damp. I thought this would rule out a leak in the shower pan or toilet. My next step is to replace the wax ring under the toilet. Another possiblity I thought of was the overflow for the A/C system that sits about 10-12 feet down the hallway in a closet w/ a raised floor, but it was bone dry and the carpet between the closet and the damp area is also dry. I went into the attic to check for any pipes running above the damp area that may be leaking for sweating from condensation and leaking down the wall, but they were all dry. I should note that the hallway wall has paneling that has become warped from where it meets the floor to halfway up the wall. This could be from a previous slab leak that was repaired a few years ago though.
Any ideas on what I can check next and if I'm on the right track?