Urine-indicator dye

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Urine-indicator dye is a substance which is supposed to be able to react with urine to form a colored cloud in a swimming pool, thus indicating the location of people who are urinating while they are in the pool.[1] A 2015 report from the National Swimming Pool Foundation called this "the most common pool myth of all time", with nearly half of Americans surveyed by researchers believing that the dye existed.[2]

Rumors of this chemical's existence go back at least as far as 1958,[1] and the story is commonly told to children by parents who do not wish them to urinate in the pool.[2] A 1985 biography of Orson Welles describes him using such a dye as part of a prank in 1937,[1] and references to the substance can be found through popular culture over quite a lengthy time period. However, such a dye does not exist, and although a chemical could be manufactured that would react with urine, it would be difficult to prevent it from reacting to other organic substances present in pool water.[1]

A few companies capitalized on this 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.[citation needed]

Acesulfame potassium has been used to estimate how much urine is discharged by swimmers into a pool.[3] In a Canadian study it was estimated that swimmers had released 75 litres of urine into a large pool that had about 830,000 litres of water and was a third of the size of an olympic pool. Hot tubs were found to have higher readings of the marker. Urine degradation products may lead to asthma.[3]

In an episode of Nickelodeon's The Adventures of Pete & Pete ("Splashdown"), a substance called "Wee-Wee See" is used to catch a pool-peeing perpetrator.

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


  1. ^ a b c d Mikkelson, Barbara (December 14, 2000). "Piscine of the Crime". Snopes. Retrieved September 18, 2012. 
  2. ^ a b O'Neil, Lauren (25 June 2015). "Pee, not chlorine, causes red eyes from swimming pools: CDC". CBC News. Retrieved 26 June 2015. 
  3. ^ a b Jmaiff Blackstock, Lindsay K.; Wang, Wei; Vemula, Sai; Jaeger, Benjamin T.; Li, Xing-Fang (1 March 2017). "Sweetened Swimming Pools and Hot Tubs". Environmental Science & Technology Letters. doi:10.1021/acs.estlett.7b00043. Lay summary (1 March 2017).  open access publication – free to read