Your sanitary sewer system
is very much like your water heater—you don’t think about it much until it doesn’t work. Sewers are something that are taken for granted—out of sight, out of mind—until the out of sight part stops working.
A basic understanding of the plumbing and sanitary sewer systems in your house will help you to know what to do if waste water does not drain from your house. The sanitary sewer system begins with the drains inside your house.
All of the drains from the sinks, toilets, etc. are piped to the sewer service line that exits your house underground and connects to the sewer main under the street.
Each drain has a “trap” that prevents sewer gases and odors from entering the house.
Each drain also has a roof vent pipe that exhausts gases through a chimney-like stack and admits fresh air to the drains.
Vents maintain the pressure behind the flow of drain water and wastes, thus preventing water from being siphoned out of the traps.