Hello,

I am struggling to determine the cause of a regularly occurring smell in our home and hoping someone can help point me in the right direction. I'm have reasons to believe the smell is likely sewer gas and our plumbing is involved.

First, the details of the issue:
Late last year (November / December), my wife and I were both waken (2 AM) to a horrible skunk-like smell in our home. It wasn't a typical skunk smell though as it also had a strong combination of chemical / cleaner smell with it. It was very strong throughout the second story of our home, strong enough to make us a bit dizzy and nauseous. The smell was present, but somewhat weaker on our first floor. The smell did not exist in our basement. It did not smell outside and took until morning to air the smell out of our home.

A second occurrence happened a week later. After this event, we did research and determined sewer gas as a possible culprit. We filled the floor drain in our attached garage and our basement with a bucket of water mixed with some bleach. For about two months, we were smell free. Then, it happened again.

We started filling the two floor drains with water once per month. Unfortunately, the smell has accelerated to the point where it will happen once every one to two weeks. I've experimented over the last month, filling only the floor drain in our garage with half-a-bucket of water each night. Ever since, we have not had the smell in our home.

Tracing the plumbing beneath our garage and where it flows into our basement, it joins a pipe just below where our second floor bathrooms and first floor laundry room empty before going out of the house and into the main. I'm suspecting that pouring water down the garage floor drain is creating a type of "second trap" preventing smells from coming back up our pipes.

A few questions:
1. Even if we had a dry trap in one of our bathrooms upstairs, would sewer gas ever be strong enough to fill an entire floor or home over the course of 4 hours? It seems strange to me that the smell is THAT strong throughout our home when it occurs. Note: Our bathroom doors are closed at night while we sleep (if it matters).

2. With the smell being stronger on the top floor and non-existent in the basement, should we be more suspicious of a venting issue? I'm relatively certain our traps are not dry when the smell occurs. Especially when we fill them with all with water and the smell occurs less than two weeks later. Could traps dry up that quickly in an unused bathtub or shower?

Thanks in advance for reading this long post and any advice you can pass along. Eager to get this figured out.

A dry trap can fill an entire floor level with strong sewer odors in a matter of minutes under the right circumstances. It does sound like it could be a venting issue with the toilet pulling the water out of a trap, or it could be as simple as a faulty wax seal under the toilet. I do not believe that the garage floor drain has anything to do with the odors on the top floor.

Air conditioning and attic fans are known for causing vapors when traps dry out.
Best Wishes

How much water should there be in a floor drain in a laundry room?

depends on the size floor drain..
a 2 inch would have about a cup and a half.
a 3 inch would have about twice as much and a four inch would have more than a 3 inch.