Urine-indicator dye

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Urine-indicator dye is a fictional substance thought to form a colored cloud in a swimming pool to indicate the presence of urine from people urinating while swimming.[1] Rumors of the chemical's existence go back at least as far as 1958,[1] with a 1985 biography of Orson Welles describing such a dye as existing in 1937,[1] and references to the substance can be found through popular culture over quite a lengthy time period. However, the dye does not exist, and although a chemical could be manufactured to react to urine, it would be difficult to prevent it from reacting to other substances present in pool water.[1]

A few companies capitalized on the urban legend by creating professional pool signs that warned that the pool was indeed being monitored with the chemical called "wee alert" or a similar catchy name. The signs were a strong deterrent particularly for adults.[citation needed]

The 2010 film Grown Ups and the 2011 film Take This Waltz both feature scenes in which the chemical is presented as if it were real.


  1. ^ a b c d Mikkelson, Barbara (December 14, 2000). "Piscine of the Crime". Snopes. Retrieved September 18, 2012.