There are a number of water fountains located throughout the airport, see below for the locations. Alternatively you can request tap water at any food/catering outlets.
Before Security
Adjacent to the Assisted Travel Area before you go through security
After Security
Within the main departure lounge, behind Bottega Prosecco Bar & Cafe
International Pier by the departure gates (Gate 47 & Gate 52)
Pier Bussing lounge
Arrivals Area
North Baggage Reclaim area