We are on an acreage with a septic tank and field. Our upstairs bathroom used to smell of sour gas on a frequent basis - we tried plugging the sink and nothing worked. We then had the toilet replaced as well as the toilet in the downstairs bathroom. The smell has now moved to the downstairs bathroom. We have plugged the sink, the tub, the tub drain and had a plumber re seal the toilet and it still smells. What's next???