source: silsilat ul-hudaa wa nnoor – the series of guidance and light – tape no. 133
Question #14: “Is it from the sunnah to drink zamzam water while standing?”
Shaykh al-Albaani (rahimahullaah) answers:
“Now, the Messenger (of Allaah) (sallAllaahu ‘alayhi wa sallam) drank zamzam while standing, and at the same time it is known that he prohibited drinking while standing. It is not clear here that the Messenger (‘alayhi ssalaam) drank while standing for the purpose of legislating (this from Allaah). Despite that, they will tell you that the sunnah for drinking zamzam water in particular is that it is drunk while standing. Then this was conveyed – from drinking zamzam (while standing) at the place of zamzam – to faraway countries where the water is transported, such that the one who Allaah decreed for him to make Hajj comes with zamzam and wants to give those present the water to drink, and each one stands up and drinks while standing! Why? Because the Messenger drank while standing… But was it clearly distinguished to you that he had the intention to make this a special ruling for zamzam??
If we supposed that yes there is a special ruling (for drinking zamzam water while standing at the place of zamzam), but what about in every country of the world when zamzam is brought to you, you stand up and drink standing, while we know that the Messenger had prohibited drinking while standing?
So it is true that the Messenger drank (zamzam) while standing, but what is apparent is that he did so due to the severe crowdedness, as I say with regard to some narrations from the Companion (Qudaamah bin) ‘Abdillaah al-‘Aamiree that he saw the Messenger (‘alayhi ssalaam) during Hajj walking with the people around him, and there was no driving away nor (saying) ‘please make way, please make way’… The Messenger – the leader of mankind – was there with the people around him, and no one was saying ‘make way for the Messenger!’ (‘alayhi ssalaam); there was no driving away and (saying) ‘go there,’ nor (saying) ‘please make way, please make way.’ No. So when the Messenger wanted to drink zamzam, the people were completely overcrowded around him. If he wanted to drink according to the sunnah (i.e., drink sitting) which he had established, they could trample him down until they would crush him, because although those around him were seeing him, the big crowd that was behind them could still rush over him. Therefore, when the Messenger drank zamzam while standing, firstly it is not clear that there was an intention of legislating, and secondly what is apparent is that he did that due to the crowdedness and never for anything else. So the fundamental principle with regard to zamzam water, like all waters, is that it is drunk while sitting unless there is an Islamically legislated excuse.”
 Saheeh at-Tirmithee #903