I figured out today that my bathroom shower is leaking somewhere when I saw the wet carpet in adjacent closet (there was no water on the ceiling or walls). I am new to this sort of thing. Where do I start looking for the leak? It is a one piece fiberglass shower. The plumbing is newer. My home is 4 years old and is built on a crawl space. Any help/advice is appreciated.

When I had blue pipe, I had no water hammer problems. Since replacing the blue pipe with copper 1 year ago, 21 plumbers have been to my house, most were master plumbers. Some have put: bladder on the hot water heater in the basement new PRV and main cut-off into the house in the basement water hammer arresters on hot and cold hookups to washing machine on the first floor (Prairie Home, IPC "AA" pattern arresters) backwash prevention valve on the water meter in the yard new toilet systems, insides of the tanks, 3 toilets. Strapping on the pipes at the entry in the basement Closing the water supply to every available outlet in the house will not stop it. Water hammer still persists.Sounds like a submarine for a few seconds, followed by 3 loud thumps. Then a few seconds silence. Then the submarine returns for new cycles. Lasts indefinitely. The only way to stop it is to turn the water supply to the house off at the main cut off in the house in the basement. Please give me your best recommendations to find and stop the source of the noise. Thank you.