This a shot in the dark. Someone would need to have a MH like mine to be able to know what I am taking about. I have a leak in the back bed room under the bottom drawer next to the closet. If you are ...
As stated turn off shore water and your pump. Hook up air to the water inlet about 40 lbs. you can put a shut off valve inline with a gauge down stream from tank and shut off , If you loose pressure then maybe you can hear it. If Pex you can go up to 60 lbs plus depending on temp and retest.