The sewer works as a gravity drain line to allow the sewage waste water to slowly drain down hill inside a pipe, off your property, and fall into the sewer main in the street. It is designed to run underground till it gets to where the toilet will be, and then rise out of the ground, upwards att the way through the roof and open into the air. This is a DWV system (Drain, Waste, and Vent)Branches are plumbed into the main sewer to allow connection for your toilets, showers, sinks,and laundry. If a bird or squirrel has nested in the roof vent, then six gallons of waste from the toilet drops into the sewer, but doesn't have enough air behind it to allow gravity flow, so the weight of the water sucks the water out of the sink p-trap, and also deposits fecal material on the pipe sidewalls. When the majority of the water drains away, the area is dark, warm, and moist, and aerobic bacteria colonies throng to the nutrients and begin their digestion process. this causes sewer gas odor smell which cannot escape from the clean roof vent, so it leaks out into the house from the trap.
: Sometimes the inside of our house smells like a sewer. A new line was installed to the city main line about 4 years ago. We don't seem to have any sewer back up either. Some one told me that the outside drain pipe on the roof maybe stopped up. Could that be causing a sewer smell in the house and how can that be fixed? Thank you Janet Wright