Conduit

a water-course or channel (Job 38:25). The "conduit of the upper
pool" (Isa. 7:3) was formed by Hezekiah for the purpose of
conveying the waters from the upper pool in the valley of Gihon
to the west side of the city of David (2 Kings 18:17; 20:20; 2
Chr. 32:30). In carrying out this work he stopped "the waters of
the fountains which were without the city" i.e., "the upper
water-course of Gihon", and conveyed it down from the west
through a canal into the city, so that in case of a siege the
inhabitants of the city might have a supply of water, which
would thus be withdrawn from the enemy. (See SILOAM T0003433.)

There are also the remains of a conduit which conducted water
from the so-called "Pools of Solomon," beyond Bethlehem, into
the city. Water is still conveyed into the city from the
fountains which supplied these pools by a channel which crosses
the valley of Hinnom.