Air Pressure Test In Water Lines

Im working on buying a forclosed house, but i know that the water lines leak and in order for the inspection to pass, i need all the water pipes to not leak, im trying to find where the leaks are, so I hooked up my air compressor to an open copper water pipe in the laundry room to see if the pipes would hold air, but the pressure gauge didn't go up at all. I checked everything visiable (faucets, capped pipes near the water main etc.) and nothing seemed to be leaking air. I hear a hissing noise behind the bathtub which unfortunatly shares a wall with the kitchen where all my cabinets are. I'de hate to start ripping the back of the cabinets up unless im sure thats where the leak is. Is there anywhere else i could check or any other tests i could do to pinpoint the leak(besides turning the water on and finding the water), any help would be appreciated as i know nothing about plumbing, thanks.

Fill with 100 to 120 psi air, listen for hissing, rip out wall, repair. Thats all besides replacing all of it.

got one of them little snake scopes where you can look into a wall through a little hole?


btw; I would suggest, if possible, to remove the cabinets rather that tearing up the backs.

maybe ill up my pressure i was only using 25psi. and im not worried about the cabinets, im going to replace them they are pretty worn. i dont have a snake scope but maybe it would be worth it depending on the price, thanks for the input guys

Use a stethoscope, it will help you hear exactly where it is leaking.

just wanted to give an update- went in there today and it was infact the water line that lead to the bathtub, so i ripped out the back of the cabinet and fixed the pipe; thanks for the help