In my new apartment in Spain there is an opening in the middle of the tiled floor that reveals a ~15cm diameter pipe. This descends around 60cm and has water at the bottom and some smaller pipe connections that I can't see very well. There was some grease and grime on the sides of the pipe that I have cleaned as best I can. Water leaving the sink, toilet and bathtub all seem to disturb the water at the bottom of this pipe so it appears to be connected somehow.
- What is the purpose of this pipe?
- What maintenance, if any, does it require?
- Are there any signs of problems that I should look out for?