In The Bathroom
Toilets: Listen for running water.
Faucets: Look for drips.
Showerheads: Look for drips when the shower control is turned off. When the shower is running, look for stray sprays. Both can be stopped with plumber’s tape.
In the tub: Look for drips when the control is turned off.
Under the sink: Check for pooling water under pipes and rust around joints and edges.