Water duct is a term used to describe a system of pipes, channels, or conduits that are used to transport water from one place to another. The MAIN component of a water duct is the MAIN, which is a four-letter word that refers to the primary pipe or conduit in the system. A FLUME is a five-letter word that describes a channel or trough that is used to carry water from one place to another. Finally, a GUTTER is a six-letter word that is used to refer to a channel or trough that is used to collect and transport rainwater away from buildings and other structures. Together, these three components form a water duct, which is an essential part of many plumbing systems.