The bulk of the Roman water system ran below the city, burrowed through 260 miles of rock, and about 30 miles of above ground bridges and crossways (the arches). The entire system relied on various gradients and gravity to maintain a continuous flow. The water rushed from higher ground via the ducts and emptied into giant cisterns in the city. These cisterns then distributed the water through lead pipes which reached most of the city.
Maintenance of the ducts was a constant job being tended to by first, a paid curator, and then often labour slaves. The Roman legions were also required to build and dig in areas far from the city of Rome itself as they proceeded to conquer and inhabit further regions of the empire. the ducts provided up to 1 cubic meter of water for every person.
Aqueducts also provided water for mining operations, milling, farms and gardens.
Aqueducts moved water through gravity alone, being constructed along a slight downward gradient within conduits of stone, brick or concrete. Most were buried beneath the ground, and followed its contours; obstructing peaks were circumvented or, less often, tunnelled through. Where valleys or lowlands intervened, the conduit was carried on bridgework, or its contents fed into high-pressure lead, ceramic or stone pipes and siphoned across. Most aqueduct systems included sedimentation tanks, sluices and distribution tanks to regulate the supply at need.
Aqueducts were built because the springs, wells, and Tiber River were no longer providing the safe water that was needed for the swelling urban population.[**]
To achieve a consistent, shallow slope to move the water in a continuous flow, the Romans lay underground pipes and constructedsiphons