regulator - any of various controls or devices for regulating or controlling fluid flow, pressure, temperature, etc.

sluice, sluiceway, penstock - conduit that carries a rapid flow of water controlled by a sluicegate

conduit - a passage (a pipe or tunnel) through which water or electric wires can pass; "the computers were connected through a system of conduits"

head gate, penstock, sluice valve, sluicegate, water gate, floodgate - regulator consisting of a valve or gate that controls the rate of water flow through a sluice