Water tanks

[prv]

No, originally developed as a surgical antiseptic then found favour as a mouth wash.

Ah - you're right it wasn't originally developed for floors, but it was sold for that purpose after surgery and before mouthwash.

http://en.wikipedia.org/wiki/Listerine
http://brokensecrets.com/2010/01/15/listerine-was-once-sold-as-floor-cleaner/
(and QI where I originally heard it)

Pete