Hello, I am a new homeowner who has enjoyed learning to do tasks around the house (re-grouting in the bathroom, replacing water heater, etc...). I have a background in electrical, and know my way around a construction site, though my day job has me behind a desk. We live in the pacific northwest and have a one-story home with a basement. The kitchen is on the main floor, and every so often a small puddle (~a half pint) forms in the middle of the tiled kitchen floor. There is no moisture around the puddle, so it isn't seeping from the walls, sink, or appliances and there is no water damage I can see in the ceiling below the basement, though it is finished, and that may hide something, but I suspect I would see something. It's only myself, my girlfriend, and our cat living here, and no one knows why the water appears. It doesn't smell or look like urine, so I don't think it's the cat. I'm assuming I need to track water usage and monitor to figure out how to replicate, and then call a plumber, but has anyone experienced this before - do you have any pointers as to how I can replicate it?

My house is on a cement slab. There is a smell under the kitchen sink so I cut out a small portion of the base cabinet floor to see if something spoiled or dead is under it. Instead of concrete, an area of about a foot or so around the water pipes and drain is not cemented. It looks almost like loose charcoal or some kind of black stones is filled in that area. Is this normal? Could it be there in case of a water leak so the water seeps into the ground instead of the kitchen floor?