Water flowed into the castellum divisorium, a distribution station on the highest point of the city near the Vesuvian gate. Due to significant height differences which caused undesirable pressure variations in the water system, a series of water towers were constructed to regulate pressures in different districts within the city.
At the city's highest elevation, a water supply depot received water from the castellum divisorium. To mitigate the effects of significant altitude disparities on the water network, elevated storage facilities were constructed to maintain consistent pressure levels throughout different urban areas.