After helping Bill Ronte in the quest High Times, the Courier can drink water directly from the pump for free.
Other interactions
Tapper takes care of the water pump installed at Freeside, but one needs to pay caps if they wish to drink from it. As an alternative, one can buy bottled water from him, as well.
If for some reason Tapper is killed before the quest High Times is completed, the water from the pump will become unavailable to drink without the action being considered stealing. While no Karma is lost by doing so, if any Kings witness the act, they will attack.
His bottled water supply restocks on Mondays and Thursdays, and he always restocks purified water x12, making him an excellent resource in Hardcore mode.
When buying purified water from him, his 10mm case can be taken for no charge.
Tapper shares the same bug as Elder McNamara, Head Paladin Hardin, Scribe Ibsen and the range master, saying Antony's unique way of saying "Later." [verified]