Vermin.
A recent visit to a house, I discovered this damaged waste water pipe.
I have had many calls for leaking pipe, only to find that mice or rats have chewed through the pipe work. Recently I discovered this waste water pipe that had been chewed through. Vermin aren’t selective as to where they get their water. In my time I have had water pipes, waste pipes, dishwashers and even a solar collector. Generally, it is after bait has been placed, this makes them thirsty and they will go through anything to get to water. If you do use bait, I recommend placing a bowl of water next to it, that way you can hopefully not have to pay a plumber to fix the problem.
If you have those tell tale signs of a leak, give me a call. Meeting your plumbing needs.