En-rogel

fountain of the treaders; i.e., "foot-fountain;" also called the
"fullers' fountain," because fullers here trod the clothes in
water. It has been identified with the "fountain of the virgin"
(q.v.), the modern 'Ain Ummel-Daraj. Others identify it, with
perhaps some probability, with the Bir Eyub, to the south of the
Pool of Siloam, and below the junction of the valleys of Kidron
and Hinnom. (See FOUNTAIN T0001378.)

It was at this fountain that Jonathan and Ahimaaz lay hid
after the flight of David (2 Sam. 17:17); and here also Adonijah
held the feast when he aspired to the throne of his father (1
Kings 1:9).

The Bir Eyub, or "Joab's well," "is a singular work of ancient
enterprise. The shaft sunk through the solid rock in the bed of
the Kidron is 125 feet deep...The water is pure and entirely
sweet, quite different from that of Siloam; which proves that
there is no connection between them." Thomson's Land and the
Book.