About 15 years ago, I had not one but two small pin hole leaks, in one of my rentals. Small drips were appearing above kitchen sink and cabinets. At first I thought it was the bathroom tile leaking above, so I pulled up a lot of suspicious looking tile, put new backer board up, re tiled, then grouted, and sealed. Amen, I thought.
Leak returned next day. I took out kitchen cabinet, and found a lot of damage to the plaster ceiling, the pipes were in the bulkhead! Without tearing everything apart, I could stick my head up in the hole to see, but it was too small to get my hands and head up to do the work. I cut out the small piece of copper, and put in a compression fitting. I let everything dry up, repaired the hole, painted and rehung the cabinets.Amen, I thought.
Until I got another call, the wall was wet coming down from the bulkhead behind sink. Off goes the kitchen cabinets, and into the wall. Another pin hole! This time, I replace 5 foot of copper from the bulkhead down to the sink. repair the wall, paint, put kitchen cabinets back up. Amen, I thought.
Until 3 years ago, when same tenant calls, says it's baaack! Well, I knew where to go this time. Down go the cabinets, I open up the bulkhead on either end and in middle, and replace 8 foot of copper from the 15yo 5 foot piece over to main trunk line. Let it dry, resealed holes, painted, put kitchen cabinets back up. Amen, I say......
Sorry you had to go through this, I thought I was the only poor soul that had this problem. And it's the only major problem with a rental I ever had, and hopefully, it was my last.