Believe it or not, a recent study evaluated drinking water preferences in cats (by Wooding & Mills). This was a double blinded study done over a 48 hour period. These scientists studied cats in a rescue center, and looked at tap water versus purified water, and day versus night drinking. Much to Brita's dismay, cats preferred tap water to purified, and drank more water during the day. Good to know! Maybe our cats know something we don't know!