Hello,
In my kitchen sink I believe I have an S trap. I have noticed a sewer smell every so often. The sink hooks up to the old septic system--I think it's a septic tank--along with the laundry sink, washer, and a basement shower. I was considering replacing the S trap with a P trap to remove the odor. I was wondering if this would help. Also, there is no vent to the sink. In addition, the right-hand sink drain slopes against gravity.
Thanks for your help.