My basement has been flooding a little (1-inch or so pooled around a ~20 square foot area) for the past week or so. Whenever I pump out the water, new water starts seeping back in from through the concrete in the floor. It appears to be sewage (seems to have some toilet paper etc. in it) although it's hard to tell. It doesn't smell as bad as I assume sewage would (smells more like a muddy pond than feces), but who knows.
My question is: Can a sewer back up like this? There is no drain or clean out in the area that is backing up. There are cleanouts in other parts of the basement, but they are all dry. Is it possible that a pipe buried in the concrete floor has failed, and sewage is seeping up out of that and through the floor? If so, why would it back up out of the pipe and into the floor, but not out of cleanouts?
Also worth noting is that the water seems to stay at a certain level consistently: If I pump it out, it will come back up to a certain level, then stay at that level until I pump it out again. Doesn't seem to get deeper over time, which I assume it would if it were the sewer backing up.
Also may worth noting is that the house has old cast-iron drain pipes, and it once had integrated storm gutters that connected to the storm sewer system (so it's possible those are backing up, not the sanitary sewer).
Best Answer
I think that it is very like to almost surely that your basement is related to the city sewer drain being full. Note that while it is often referred to as the sewer or sewer system, it does not contain sewage but rather it is for rain water runoff. The system that carries waste water from your home is (depending somewhat where you live in the world) a completely separate system.
So the good news that the water in your basement is probably not sewage but just rain water. Which explains the lack of smell. The particles that look suspicious might just be dirt or other debris from the basement (these can't go through concrete anyway)
If you have not contacted your city about the water situation then I would do so, and tell them the situation and that it's flooding your basement.