The toilet I went into today had taps that you press and the water runs for a given time, I was in there nearly an hour trying to get through happy birthday x 2, I could only just manage to sing the first one before the tap turned off, then after an hour of trying I realised that if I pressed a tap on the next sink before the end of number one happy birthday, Job done, I think they need re-timing. :0)
For the avoidance of doubt, you can add all the unfinished happy birthdays together and avoid loitering in the facilities for an arrestable length of time.