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A sewer lateral is the underground pipe that connects a residence or business to the sewer line. Generally, it is made of ductile iron at least 4 inches in diameter. Some local governments consider the entire connecting pipe to be the property of the homeowner or business owner.
In other places, a city or county will assume responsibility for the portion of a sewer lateral from the main line to the property line. Sewer laterals can account for more than 50 percent of the pipe in some systems. Unfortunately, the privately owned underground section of a lateral is often taken for granted until a problem erupts that can't be ignored -- such as raw sewage backing up into a dwelling.
A number of things can compromise a lateral. Foreign substances or objects such as grease or disposable diapers flushed down a toilet can sometimes create a clog. Tree roots occasionally push through the side of a lateral. Or, over time, a very old sewer lateral pipe can simply corrode and crack.
Although local and state courts have generally ruled that public funds should not be used to repair private residences, sewer laterals are often granted an exemption because of their direct connection to the general health of the neighborhood. Sewage or contaminated water that escapes from a sewer lateral can often seep into the communal water table, thus becoming everyone's problem. With this in mind, cities all across the U.S. have initiated programs over the past 10 years to help with -- or, in some cases, absorb completely -- the cost of fixing defects or breaks in lateral pipe.
Responsibility sometimes becomes complicated, however, when several houses share the same lateral. Generally, the sewer lateral runs slightly downhill to the main line, allowing gravity to do most of the work. A Y-fitting and vertical pipe hooks into the lateral close to its origin to provide access to the larger pipe.