We have a half bath downstairs in a two-story home on septic. Occasionally (every 7-10 days) we get a strong odor in the half bath. It seems like sewer gas, propane, or a dead mouse. The other two bathrooms do not have this. This post suggest a wax ring issue which I will investigate.

I wonder if it could be something else though. I installed the toilet about a year ago and was pretty careful with the wax ring. This summer we had a partially clogged leach field. If we used a lot of water in a short time, say 3 showers in a row, and washing clothes, we would get some seepage out of the cleanout cover. I'm remediating it with an Areo-Stream and the field seems to have been flowing correctly for several months. When the septic system was clogged, we could hear the wastewater "chug-a-lug" through the pipes. Just wondering if the smell could be related to the septic issue.

2 Answers 2


Try checking the vent for the pipe. A lot of times if the vent is too small or partially clogged it will cause this problem. I had the same problem & found a partial bird nest in it. Cleaned it out & resized vent under sink up to 2" & it worked fine afterwards. Is worth a try. Should be a vent for each sink and/toilet, (1 for each room) & right height & size. Good luck with it.

  • + birds and squirrels for me with leaves can cause the problem + if the wax ring there is usually a leak but not always, any floor drains? They could be drying out.
    – Ed Beal
    Jan 31 at 20:37
  • I wondered about the vent. Unfortunately it's a 2 story house with a 12/12 roof and currently covered in snow. May have to wait for spring.
    – ptiemann
    Feb 5 at 4:10

If you don't have a vent under the sink, you can mount one if your a little handy. Otherwise you may need to call someone to try & clean it out. A Thought, a simple way to tell if it's the venting is to flush your toilet & shine a light down the sink drain pipe. You want to be able to see the water in the trap, if you see it (the water in the trap) move when you flush the toilet the vent is most likely clogged. Hopefully this helps. Otherwise, take a couple of photos & show how it's setup up. Have a better day.

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