How many tubes did the aqueduct have

The main source for the aqueduct was the spring of Chapultepec and the purpose of the twin pipes was to ease the maintenance of the system, because the water was conveyed through one pipe, and when it got dirty, the water was diverted to the other pipe while the dirty pipe was cleaned

Explanation:

   It consisted of a twin pipe distribution system made in part of compacted soil and in part of wood for the crossings of the aqueduct over the bridges built to allow the passage of the canoes. It was finished around 1466 AD, and the main purpose was to supply fresh water to Mexico-Tenochtitlan, to mitigate its thirst.

   The main source for the aqueduct was the spring of Chapultepec and the purpose of the twin pipes was to ease the maintenance of the system, because the water was conveyed through one pipe, and when it got dirty, the water was diverted to the other pipe while the dirty pipe was cleaned and, if necessary, repaired (Palerm, 1973).

answer; the period of time known as the middle ages;

the term is einsatzgruppen