We had a huge backup from our basement drain about a year ago (little children and too much paper in the toilet caused it I think). We cleaned up the concrete floor with cleaner and then with bleach and took out the carpet that got wet. All was fine for a while, then the smell started. We get a sewer stench off and on that seems to start in that room where the drain is (it is also the laundry room) then it will spread throughout the house. I also notice it sometimes coming from the 1st floor bathroom sink and shower drain. We also now have these little funny looking flies that hang out in the basement. The biggest number is right by that drain. I have tried drain cleaners and bleach. Every time I pour stuff down the drain, some of the fly things come up. An exerminator that was at the house for another reason saw one of the flies on the wall and told me it was a sewer fly and that I probably had a problem with one of my drains. Can I clean out that basement drain and pipe? Do I have a big, expensive problem that needs a plummer?

The same thing happened to us last year, right around December too actually. We had to get the intire pipe connected to my house and a street (how ever it works) changed. How old is your house?

Before you take any action you must first locate the source. The floor drain trap. Does it hold water? You should have about three inches of water in the floor drain trap. Take the strainer off and check. If not then you need a plumber to replace it. Good luck, Tom

Are you sure you are connected to city sewer and you do not have a septic tank? It sounds like a full septic tank to me. The smell will start from the first drain in you line and work its way up. If you are on septic, have it drained.(about $300.00). One quick way to find out if you are on city sewer is to make sure you have "man holes" on your street or ask your neighbors.
Good luck

The house was built in the early 70's, so it is about 30ish years old. We are definitely on city sewer (I called to ask after you posted that). There is water in the drain trap right now-it is kind of gross looking (but that could be because it is dark). There is a little bit of the sewer smell when I get right up on the drain (to look for the water). The pipe is rusty and gunky looking above the water level. The water comes up to about 2-3 inches below the grate in the floor. My husband grew up in the house and they never had the problem before we had the backup.