Amount of Water for the After-Blessing
Question
Answer
Hello,
The general rule is that one must drink a revi'it of water within the appropriate time for drinking a revi'it.
Therefore, if 150 ml is consumed within the usual time, an after-blessing is required. However, if this amount is consumed slowly, no after-blessing is recited.
In cold water dispensers, it is common for the water to flow slowly, and then the drinking takes place over a longer period, and in such a case, no after-blessing is recited.
Source
Mishna Berura, Siman Reish, Se'if Katan Aleph, brings two opinions on the amount of drinking a revi'it, as explained in Shulchan Aruch, Orach Chaim, Siman Taf-Reish-Yud-Bet. In cases of doubt regarding blessings, one should be lenient.
Also, regarding the amount of a revi'it, Mishna Berura, Siman Reish, Se'if Katan Bet, brings the dispute mentioned in Siman Reish-Ayin-Alef, Se'if Katan Samech-Chet in MB and Be'er Heitev there, and in Siman Taf-Peh-Vav in MB and Be'er Heitev.
And in this case, one should be lenient.