I have a downstairs restroom for guest with only a sink and toilet. For the past few days there is an odor coming just from that room. I also noticed that the odor is worse at night. I got up last night around 3 am and the odor was really bad. It is the closest drain to the septic tank. We had the septic tank cleaned out about 3 years ago. There is no odor coming from the kitchen sink nor from the laundry room that is also downstairs. We also replaced the toilet in this bathroom about 2 years ago so it is a new toilet. But the sink was here when we bought the house and the house is about 23 years old.

get down real close to the floor at the base of the toile and have a good sniff. sometimes the wax seal will not leak water but will not seal 100% so an odor can sneak out..
if you suspect that is it, wrap a damp towel securely around the base to seal it. if there is no smell the next day then the toilet needs to be reset.

If the sink hasn't been used in a few weeks it could be that the water in the trap has evaporated.

Thank you so much !!!! I got down in the floor like you said and got right at the
bottom of the toilet and the edge of the floor and I can smell it. We just had that toilet put
in in just the past two years and when my husband got down in the floor the toilet actually moved. So the person that put it in didn't tighten it up good. I have tightened it to see if it stops the smell. Thanks !!!



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the flange needs to sit ON TOP OF the finished floor

and

the flange needs to be securely anchored to the sub-floor

then

the toilet is 'bolted' to the flange



for illustration only, your floor may be different:


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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Thank you for the info. We are probably going to have to take the toilet up
and check on the wax ring. The info will help us know if it is fixed the right way. I was
able to tighten it down but I can still smell the odor but it is not as bad as it was
before.
Thanks for the pic.

You may have one of two possible issues here. Firstly, it is possible that you have a cracked vent pipe. The vent pipe carries the odor up to the roof and out of the house. If the vent pipe is cracked or broken, the odor will be detectable inside the house. This pipe is typically concealed behind a wall. The best way to detect if the vent pipe is damaged is to video camera the line. Doing this will show if there are any cracks or breaks allowing foul-smelling air to escape into the house. Another way to detect if there is any kind of fracture in the pipe, we do a smoke test. This involves forcing smoke under pressure into the vent pipe and then determining if this smoke appears anywhere else in the building. This would indicate a broken or damaged vent pipe.
The other place to look is the wax ring that the toilet is seated on. Remove the toilet, and check to see if the wax ring is damaged. If it is, it needs to be replaced, or you can even place a second wax ring over the original. Re-seat the toilet on the new wax ring and you should be okay. It also helps if you caulk the entire area around the base of the toilet. Hope this helps.
Compliments of Greg R., master plumber



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