Is There a Urine Detector for Swimming Pools?

He could pee in the pool and no one would ever know. Pool urine indicators are only an urban legend.
brokenchopstick, Flickr Creative Commons
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated April 16, 2018

Have you ever wondered whether there really is such a chemical as a pool urine detector or pool urine indicator dye? Such a dye supposedly clouds the water or produces a color when someone urinates in a swimming pool, as we've seen in movies and on TV. But does a urine indicator really exist?

Is There Truth to the Rumor?

No. There is no chemical which changes color when someone urinates in a swimming pool. There are dyes which could cloud, change color, or produce a color in response to urine, but these chemicals would also be activated by other compounds, producing embarrassing false-positives.

Though there is no such thing as a urine-detecting dye, you can purchase signs that prey upon the misconception that a urine indicator exists. The signs, which warn the pool is being monitored with a chemical "wee alert," are believed to be an effective deterrent against urination in a pool, particularly with adult swimmers.