The fountains can be found in the following locations:
At the firehouse.
After you enter the Sedgewick Hotel, the soda machine room on your right.
After the water drains from the hallway but before you reach the Sargassi Lounge, the corner of the elevator lobby.
In the laundromat Zeddemore breaks into at Times Square. By the cursed artifact, pushing bone, in the back room.
After the cut-scene of Hoss and Stanz and the two office workers in the elevator at Times Square, you will be at the architectural office. The fountain is at the corner of the hall.
In the Public Library hallway leading to the juvenile reading room.
After the Egyptian and Mummification exhibits at the Museum, Venkman will spring out to surprise Hoss and Zeddemore in a maintenance hallway. The fountain is there, right next to the Azatoth Head artifact.
When revisiting the Sedgewick, you need to turn the power back on at the generator room. The fountain is in the generator room.