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).

  • 1
    Is actually coming our of the floor, or is it coming out of a pipe that comes out of the floor?
    – SteveSh
    Apr 23 '20 at 23:17
  • @SteveSh no pipe is visible where the water comes out. But maybe there is a pipe buried farther under?
    – gadolphus
    Apr 23 '20 at 23:35
  • have you had unusual rain lately? or has the weather been dry? Any other changes inside or out from around the time that it started?
    – Ack
    Apr 24 '20 at 0:19
  • 1
    If you're seeing bits of toilet paper or anything floating in the water which wasn't in your basement already, then it's not seeping through the concrete - it's flowing in through a hole.
    – brhans
    Apr 24 '20 at 1:30
  • 1
    Can you turn on all the water in your house and let it drain, and this stays at the same level or rises?
    – DMoore
    Apr 24 '20 at 3:22

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.

  • 1
    I don't know where you live, but here in the UK many older developments are on "combined sewer" systems where the sewage and rainwater are taken away by the same pipes. Apr 24 '20 at 4:04
  • Thank you. I will call the city and hope I can get someone to come out and investigate why their drain is filled to the brim. Also, re: the smell, how bad would sewage backup smell? My basement currently does not smell pleasant, but it's certainly not gag-inducing either. It just smells kind of off damp or muddy, but not like feces that has been sitting stagnant for a long time. Could sewage smell only a little off, or would it smell very, very bad?
    – gadolphus
    Apr 24 '20 at 11:23
  • Where would the toilet paper come from? Sounds like sewage to me.
    – Ed Beal
    Apr 24 '20 at 14:42
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    @EdBeal this assumes that the OP is in fact seeing toilet paper, and I believe that they are not at all certain "seems to have some toilet paper etc. in it"
    – Ack
    Apr 24 '20 at 18:33
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    gadolphus: re how bad raw sewage smells and if you have it in your basement, let me answer this way, if it was sewage you'd most likely know without a doubt. During collage getting my civil engineering degree, we got an in depth behind the scenes tour of a waste treatment plan. There is no doubt about which was is the raw stuff flowing into the plant... You say it just smells kind of damp or muddy, this is what a moist place smells after a while. I'm going to guess that the water is actually smell free, and what has happened is that it has 'liberated' the smells already in your basement
    – Ack
    Apr 24 '20 at 18:38

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