Affinity Water serves Slough, which is home to a number of data centres (40 and counting), and said some individual facilities request supplies of up to 35 litres of water per second, equivalent to the peak water demand of 3,500 homes.
Article source: https://www.huffingtonpost.co.uk/entry/how-much-water-data-centres-use_uk_6a8330bfe4b0ddd9c1b2e6d5