Taps were commonplace on bathtubs. According to one account, baths could be filled using one or two taps by one or two Autons. (GAME: U.N.I.T. Initiation Test [+]Justin Richards and Gareth Roberts, Doctor Who Annual 2006 (Panini UK, 2005).)
There was a tap on Moira's bathtub. (TV: The Pilot [+]Steven Moffat, Doctor Who series 10 (BBC One, 2017).)