FOLLOWUP! In July 2012- I had sewer gas leaking into my bedroom, bathroom, and then up to the upstairs level of the house for five months. It was awful. I have an 18 inch crawlspace and a raised floor. Under the house is dirt and the pipes. I had FOUR plumbers and TWO handymen check it out. They found NOTHING! They were too big to fit around the pipes!!! We had put in a new toilet, and I had that pulled up and put down again, just in case. but that was fine. We checked all the traps, and now keep them full of water, so they are fine. The plumbers gave me estimates of $4500 for a sewer cleanout installation in front of the house, and $6800 to repipe the bad pipes, if they found any.... I did not have the money, and they really had no plan, just guesses. Last August 2012, I luckily found a neighbor friend who was able to crawl around under the house. He was a little guy, and knew how to do plumbing and other repairs!! He found leaking and large cracks in the main drain sewer pipe at the ground level, around the back of the pipe, hidden from general view and he used epoxy to repair it. This pipe was attached to other pipes, and if it needs to be replaced it will be a difficult job. That pipe was directly below the downstairs bathroom. That reduced about 70 % of the smell and seems to be holding tight with no more leaking there. But sewer gases were still leaking from somewhere else, but not as bad, or as often. it still kept coming back about every three days.They centered in my bedroom, and seemed to come out of the floor. Oddly, from the beginning, the gases only happened around 1am until 5am, then stopped all day long, so no one could smell them, unless they stayed all night. From the first repair, the gasses only occurred about every three days or so, and not as severe, but still stinky. My friend came back into town in November, and went back under the house, and found stress marks on the larger pipe that attached to the MAIN drain sewer pipe, and ran towards the front of the house. This pipe traveled directly under my BED, and the cracks were basically under my pillow area. (What LUCK!) He had to replace that whole pipe, and to get it inside we opened the ground vents and slid it through, and the old pipe out. After he replaced that and all the fittings, the gases were gone! THANK YOU GOD!!! It cost me $800 just to investigate all this, and get nothing for the repairing of it from that! Plumbers were just ready to get paid, with no idea what was actually wrong!!! My friend only charged me $550 plus parts for this! I suffered through it for five months, and hope the sewer gases didn't harm me in any way! I sure appreciate the clean smell now!!! By the way, it was an acrid stinky burning smell. It did NOT smell like METHANE, or anything described as general sewage smells. It was just hard to breathe it, and would cause eyes, throat and nose to burn. I had a runny nose right up to the day the last pipe was replaced, and it all stopped. GOOD LUCK TO ANYONE STILL HAVING THIS PROBLEM. I learned far more about plumbing than I ever thought I would need to know!

I don't see how any toilet - save one on a boat or R/V - could possibly function without a vent stack. "but the vent goes to the garage" would not be approved by any building inspector anywhere in this country. Perhaps it was a "SPOT" - stupid previous owner trick. There is one possibility - other than installing a toilet and vent properly - which apparently was not done. The vent or soil pipe could have been pierced by a drill, nail or screw, especially if PVC was used. As an appraiser. I've seen that happen before. And yes, I *almost* made that rookie mistake myself, installing a new cabinet over the toilet. Since this is a 1938 house with plaster on lath walls, I was using a stud finder and drilling pilot holes. One was in an unexpected location, but it was *perfectly* placed. But it wouldn't drill...and that's when I realized it was the cast iron vent stack. No harm done....

I had sewer gas smell in my house. It was VERY bad in cold weather at night. The cause was roots growing in my outbound sewer line before the pipe meets the main sewer at the street. First plumber put camera down toilet pipe. He saw roots in the line. The plumber put the snake down the toilet and removed a lot of roots from the pipe going from the toilet to the street. The sewer gas smell is completely gone after that. Afterwards I put copper sulfate down the toilet to retard future root growth. You can buy copper sulfate at a hardware store. First the snake has to be put down the toilet to cut and remove roots that have gotten into the pipe.

Could I have a clogged roof vent? Possibly Backed up septic (pumped 3 years ago, live alone)? Probably not since it drains fine. Bad valves? Possibly If you have roof vents why do you need the AAVs? I get the feeling the AAVs are sticking open. Either bad design or need cleaned and lubed or something. This is one reason to avoid AAVs they require maintenance and are another thing to break or not work.