There is nothing worse than the smell of sewer gas in your home. This is especially true if you live in the country like I do because we have septic systems or on site sewage disposal units out here. The close proximity of the waste storage unit to the home makes the potential odor from uncontrolled sewer gas even more pronounced. Recently I had an issue with a hard to cure sewer gas odor coming from one of my bathrooms and this is what I learned.
For starters, I learned that most odors are caused by a malfunction of your P Trap. Every drain that leaves your house has a little curve in it that traps water. This water forms a physical barrier to keep sewer gas out of your home. If this water drains from the P Trap, you can get odor from the drain. The tricky part is finding out why your P Trap dried up and correcting the issue.
The most common reason is that the drain does not get used often. If it does not regularly see water, the water in the drain will simply dry up from evaporation. Easy enough to fix, just run water into the drain for a minute and voila, you have a functioning P Trap and your odor should disappear. Sure enough, I have a tub in the offending bathroom that never gets used. I ran the water for a minute and the P Trap in that drain was surely good to go. Well, maybe not. In a couple days I noticed an odor again.
So what else can cause a P Trap to dry up? Well it turns out that every drain must also have an air vent that will exit through the roof. If you go outside your home you will see a few open top pipes sticking out of your roof. They don’t put caps on these because if it rains, the water entering them would just flow down the drain. Problems can occur if these pipes get clogged. When a drains vent is clogged, it will suck the water out of nearby P Trap when it drains. Then you can get odor out of the now dry P Trap. The solution to a clogged vent is to take a hose up on the roof and run some water down those vents to make sure they are clear and free of birds nests, etc. I did this to all of the vents in the area of my problem and crossed my fingers. But alas, a few days later, there was that offending odor again.
So now, I am getting pretty frustrated and am ready to just put corks in every drain in the bathroom. I am 90 percent sure it is coming from the shower drain at this point but I can not seem to stop it. So, I pop the screen off of the shower drain and take a good look into it with a flashlight to make sure that there is water in the P Trap. It was recently used so there was water in the trap but there was also something else, hair. Long hair. It wasn’t enough to clog the drain but it was long enough to potentially slowly wick water out of the P Trap and dry it out. I cleared the clog, put the screen back on and once again crossed my fingers.
So, did it work? I am happy to say that it has been over a week now and I no longer have that horrible sewer gas odor in my home. So, If you have a persistent problem with sewer gas in your home and nothing else has worked, take a good look inside those drains. It might be something as simple as hair wicking the water out of the trap.