Underground conduits are pipes or tubes that are used to transport materials such as water, gas, and sewage. The term 'underground conduit' can refer to three different types of pipes: a SEWER (5 letters), a gasline (7 letters), and a watermain (9 letters). Sewers are used to transport wastewater and sewage from homes and businesses to treatment plants. Gaslines are used to transport natural gas from the source to the consumer. Watermains are used to transport potable water from the source to the consumer.