A Lacus, public fountain in Pompeii (Reg VI ins 14 South-East corner)
"Frequent rounds must be made of channels of the aqueducts outside the City, and with great care, to check up the granted quantities. The same must be done in case of the reservoirs and public fountains, that the water may flow without interruption, day and night."
Frontinus - The Aqueducts of Rome II.103
Translated by Charles E. Bennett