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According to Canadian researchers, a 220,000 gallon pool, which is about one-third of an Olympic-sized pool, had 75 liters of urine while another smaller pool (110,000 gallon) had 30 liters. This determination was made by taking samples from 31 different pools and hot tubs in 2 different cities over a 3 week period. The urine marker they looked for was acesulfame-K which is an artificial sweetener that is completely excreted from the body with urination.
That said, urine is "sterile" and should not trigger any infections whereas fecal matter is the responsible infectious vector which explains why swimmers tend to get ear infections (otitis externa or "swimmer's ear").
However, given how much poo and pee is found in swimming pools, this info just reiterates how "dirty" the water is with human excrement and appropriate awareness and vigilance should be maintained by swimmers.
Sweetened Swimming Pools and Hot Tubs. Environ. Sci. Technol. Lett., Article ASAP DOI: 10.1021/acs.estlett.7b00043. Publication Date (Web): March 1, 2017