Sewage and sewer gas make a house smell. Remove the smell with bleach and vinegar. If your problem is a sewage leak, have a plumber come out and fix the leak before cleaning the surface. For sewer gas problems, first try cleaning out the drains. Drains have water inside of them that block sewer smells from entering homes. The water can dry up if the drain isn't used much. The odour sewage and sewer gas lets off can be harmful to breath, so remove the smell as soon as possible.
Pour 2 cups of bleach down each drain, including toilets.
Flush out the drains with water.
Pour 2 cups of mineral oil down rarely or never used drains. Repeat every two or three months.
Pour straight white vinegar on cloth surfaces that have been exposed to sewage. If these areas can be bleached, cover in bleach instead.
Let the vinegar or bleach soak into the surface to kill the odour. Mop up the excess.