Basement Sewer Gas Odor

I recently purchased a home with a partially finished basement. The basement has a slight sewer gas odor that I've had trouble pinpointing but it does seem to be strongest in the bathroom which consists of a toilet, sink and shower stall. From a very close nasal inspection, the odor does not seem to be coming from the shower stall drain. The toilet has water in it so I'm assuming that would not be the source, which leaves the sink. I've heard that "S" traps can have problems and I'm not sure what one looks like but, the sink has a "P" trap. This is a spare bathroom ( there is a full bath on the first floor). The only thing I could think of is that the prior owner, an elderly woman, probably did not use this bathroom so it may not have been used for a very long time and the water seal in the trap simply dried up. Does that sound like a possibility? I ran the water to put water into the trap but I will not be back at the house for another week to see if it has made a difference. Could the water in the trap dry up in a weeks time? If this doesn't solve the problem, any suggestions for what to look at next?
George
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Usually take longer than a week for it to dry out. We have a drain at work that is rarely used and it will dry out and odor appears. Quick flush fixes it for weeks at a time.
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Does the basement have a floor drain ?
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In addition to the other posts, water can get removed from a trap due to a clogged vent pipe or improper venting even if the water is coming grom another drain. As the watter passes by, a small vacuum is created that can lift some water out of the trap(s). John
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snipped-for-privacy@adelphia.net wrote:

Run about a quart of water into the shower and sink drains. That will refill the traps.
If the odor persists and there aren't any floor drains to account for it, the seal under the toilet may be leaking. A dried out seal will allow gas to escape even though there is no visible water seepage.
Jim
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The shower drain is in the floor. I'm not sure how it is plumbed but the floor is a cement slab. I'm assuming that they ran the drain below the slab. If, by floor drain, you mean an open drain in the floor then no, there is none. When I go back I'll run water into both the sink and the shower drain. Thanks for the suggestion on the toilet. I would never have considered it since it was tight. If the odor does not go away I'll replace the seal.
George
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The shower drain is in the floor. I'm not sure how it is plumbed but the floor is a cement slab. I'm assuming that they ran the drain below the slab. If, by floor drain, you mean an open drain in the floor then no, there is none. When I go back I'll run water into both the sink and the shower drain. Thanks for the suggestion on the toilet. I would never have considered it since it was tight. If the odor does not go away I'll replace the seal.
George
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It's my understanding from having recently gotten quotes for a bsement ejection system that will be needed for a bathroom basement, that that type of system could also cause the smell you describe....
snipped-for-privacy@adelphia.net wrote:

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snipped-for-privacy@adelphia.net wrote:

It could use an in-house vent. If so, check that the thingy they put on the end of it still works.
--
Thank you,



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