I have a 3 story 10 old townhouse in chicago. In third floor, When either the faucets in my sink or bathtub be turned on, I will hear a water drop like noise coming from the wall. In the second floor ceiling, I can see the water mark. I know there is a leak in the returnning water pipe inside the wall.

I wonder what is the right procedure to ask a RIGHT plumber to come to see it? Ased one plumber 4 month ago, he said somewhere else have leak problem. Now with the noise louder and clearer, the leakage is easier to recogniced than ever. Do I need to hire someone first to open the second floor ceiling first? Is there anything like x-ray can see through the house and diagnose it?

By the way, is this serious?