unidentifiable Condo leak below bathtub

[eg]

It was my a/c.... leak detector came out today and ruled out all pipes first. He went right to the a/c and ran a hose from the bathroom sink to the recirculating pump. The water started flooding the unit below... a/c guy came back (I called him first last month..) and replaced the plastic tubing with copper. Can't believe the a/c guy didn't suspect that when he came out last month. very dissappointing and a waste of time and money trying to figure this out. Thanks for all your help.