Answered by: Maulana Abrarul H. Hasib
Is the buying and selling of zam zam water permissible?
In the name of Allah, the Most Gracious, the Most Merciful
Yes, selling and buying ZamZam water is permissible.
Zamzam is preserved in bottles and preserved water is owned, hence selling and purchasing it will be allowed. 
Only Allah knows best
Written by Maulana Abrarul H. Hasib
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Raddul Muhtar, Vol. 3, Pgs. 268-269, Dar Alim Al-Kutub