Q. Can one drink from a water fountain on shabbos? Are there different types of water fountains? Thank you.

A. Some Poskim (Sheorim Hametzuyonim Behalocha / Kuntres Acharon 2,73,43) compare a refrigerated water fountain or a water cooler to a refrigerator. In their opinion, if you are lenient in opening this device even when the compressor is off, the same would apply to using a water fountain, regardless whether it is connected directly to the water main or it has its own replaceable water container. In regards to a refrigerator, many Poskim are Makil in the opening their doors. Some are lenient only when the compressor is on (Igrois Moishe O.C. 2,68 – Har Tzvi 1,151- Minchas Itzchok 2,16 – Shemiras Shabbos 10,12 ). Some Poskim permit opening the door even if the motor is off (Minchas Shlomo 1,10 – Tzitz Eliezer 8,12 – 12, 92 ). The opinion of the Chazon Ish is to be Machmir altogether, unless the device is connected to a timer, (Chut Shoni – Shabbos 1 p.199). Some authorities (Teshuvos Vehanhogos 1,220), permit opening them only with a shinui, (doing it in an unusual way), such as using an elbow.
Other Poiskim, however, differentiate between a refrigerator and a water fountain or cooler. Some permit those that have a container and prohibit those connected to a main, where fresh water that requires cooling enters them. (Mishne Halachos 11,279 – see B’er Moishe 6,58).

Horav Shlomo Miller’s Shlit”a opinion is that a refrigerated water fountain or cooler is unlike a refrigerator, for two reasons: 1) The effect of the incoming temperate water (even if held on a container) is more direct and immediate on the thermostat, than the warm air entering a refrigerator. 2) Unlike a refrigerator’s door that remains open, you have to keep constant pressure on the opening valve of the water cooler or fountain, to let the water flow. He would only permit using a water cooler only,“letzorech godol” (in case of real great necessity), if done with a shinui.

Rabbi Abraham Bartfeld as revised by Horav Shlomo Miller Shlit”a