I have 2 story house. My guest bathroom is above my kitchen downstairs. Whenever someone upstair is using sink or toilet, I hear water dripping on the ceiling when I'm standing in the kitchen downstairs. It doesn't drip when bathroom is not in use. I just bought this house over a year ago. It's a brand new house with sorry a*** plumbing. I was just curious what kind of damage I'm looking at and about estimate expense? I'm new to plumbing and I have never owned a home and I get stressed when I get plumbing problems in a new house.

See if you can see where the water is coming from in the bathroom, under sink, behind toilet, there usually is shut off valves for these, if you can't see any leaks it could be the plumbing behind the wall for the shower, or it could be they didn't place your toilet down evenly and the wax ring is leaking, these are just ideas, its hard to tell with out looking right at it or being there.

Is your kitchen ceiling drywall? You might need to poke a small pencil hole to see if the water is puddling but eventually a large portion will need to be removed. You can't see it yet but there is mold growing on the top side of the ceiling.