Nehemiah described the stairs that went down to the spring of Siloam from the City of David (Neh. 3:15–16) and the fountain gate at the base of the stairs (Neh. 12:37).
All of that water from the spring was necessary for the performance of sacrifices in the temple. The numerous sacrifices made could not have been satisfied by water from the cisterns inside Herod’s fortress.
Aristeas (c.285 BIA) explained how the landscape of the temple area was designed with paved stones and gutters to carry away the blood washed down from the sacrifices. There was an inexhaustible supply of water gushing into the temple for sacrifices (Aristeas 87–89). This suggests that part of the temple was built over the spring or else the temple was so close to the spring that water from the spring could be directed from it into the temple itself.
This bathing place required flowing water with a canal around it so the bath water, like the blood, could flow away into a drain that escaped into the ground (1QT 32.11–15). This mixture should not be touched before it vanished into the ground, because it would be defiled with blood (1QT 32.14–15). Rabbis said it would flow into the brook Kidron (mMid 3.2).