: Yes, one MORE person asking about the smelly basement problem. I read some of your posts on the subject, and while informative, no one seemed to have my particular issue. So, I am posting it now. Okay, here goes. I live in a very old house, built in the 30's. It is also a rental, so I have no idea of WHAT has actually happened to the pipes, how old they are, what the floors might be covering, what might be in the ground outside the basement walls, etc. All I know is that there is a terrible smell in the basement that smells very highly of ammonia. At first I thought maybe a drain in the floor, but there isn't one. I am wondering if there is one of those P-drain things I saw in one of your other posts. There might not be in the pipe from the washer, and that could be it, but I am not sure. Anyway, I also thought maybe the carpet down there, so we removed it. The smell improved, but it is not gone. It also seemed to be coming from a damp crack inthe floor, but when we tested the wetness with a PH strip, it turned out to be a base, like from the laundry soap perhaps. I thought about sealing the floor with a cement sealer to see if that took the smell away, but what if it doesn't? What would be the most likely cause of this smell? The age of the house possibly? Or is it a greater possiblity that when someone put a washing machine down there, that they did not bother to put that drain in there containing the water "plug" as you put it? Anyone with an idea jump in here! Thanks!
When it smells like ammonia, it's mildew, not sewer gas or p trap gas. The basement is cooler and lower than the rest of the house, and lower than the ground, and gets the moisture from rain and lawn sprinklers collecting at the outside concrete block walls. Those blocks are a little bit porous, and so a little bit of water seeps through over time, but not enough to noticibly observe.That is just enough moisture to feed mildew, and let it grow. But the basement is also dark, and no sunlight shines in brightly enough to apply ultraviolet rays to the mildew (like it can in the upstairs rooms[ but like it sometimes does in the bathrooms]) Sunlight kills bacteria and mildew. So does ultraviolet light. But as the bacteria and mildew breeds it consumes oxygen in the air, releasing the ammonia odor. Any commercial mildewcide, or bathroom tub abd tile cleaner will clean it up. Isn't this a GREAT website?