I recently moved to a new apartment. Bad thing, on Friday of first week in the new apartment, I got a call from a plumber -- he was in the apartment below mine there are notable amounts of water dripping from the ceiling. He would like to have a consultation with my water installation.

Long story short. This is what he found after two visits and removal of my shower base plus digging up parts of my bathroom floor and wall:

What we see here is a warm water pipe which had previously been perforated. But instead of calling a plumber to fix it, some fucking idiot* had the outstanding idea of fixing it with a bicycle puncture repair kit.
This is the punction of the warm water pipe as such:
... it lost one drop approximately every three seconds. Based on the assumption of each drop being one ml, that makes 28 liters each day dripping into the house.

* If the shitty bonehead who had this fucking idea wants to complain about me insulting him or her, he or she may feel free to drop me a mail at ad001 (at) uni (dash) rostock (dot) de. I will most happily forward it to the apartment owner who in return will gladly forward all bills resulting from this idiotic try to avoid spending 50 euros for a plumber to fix an accidential puncture.

Update 2016-01-14

Yes, the "repair" was hidden under some adhesive tape. Pieces of it can be seen on the first picture.