When she was a child, Jazmin Delfi and her family visited the Swann Memorial Fountain at Logan Square to swim.

On Tuesday, she watched her son swim in the fountain, reflecting on her own childhood memories as a 6-year-old playing in the water.

“That’s what [the fountain] is just known for,” said Delfi, a 25-year-old South Philadelphia resident.

Despite the small crowd swimming on Tuesday, that activity is banned at the fountain, according to the city’s Parks and Recreation Department. A small sign hung near the fountain lists no swimming, in small letters, among a handful of other prohibited activities.

Delfi said she knew about the rule, and has seen park police walking around in the past. But that didn’t stop her.

Alain Joinville, a spokesperson for the Parks and Recreation Department, said swimming is allowed on city properties only when a lifeguard is present. So why do people swim in the Swann fountain? An Inquirer reader noticed the fountain’s growing summer crowds and submitted that question to Curious Philly, a forum where readers can ask questions about the city and the region.

“If you ask me, I just think it brings us all together,” Delfi said.

While it may be fun, swimming in a public fountain presents a health risk, the city’s Public Health Department said. The water undergoes vigorous treatment, the same as drinking water, but once in the fountain, "it’s essentially like a pool, but without all of the treatment chemicals to make it safe.” The department discourages swimming in fountains.

“The Health Department inspects pools to ensure that they have been treated properly to allow for swimming, but this is not the case in the fountains," Joinville said.

He said the Parks and Recreation Department encourages the public to cool off at one of its 70 public pools or 130 spray grounds. Rangers perform “spot checks” on the fountain and may cite anyone caught swimming in a fountain, he said, noting a spray-ground and wading area across the street at Sister Cities Park.

Cryptosporidium and giardia are two main illnesses of concern, according to Health Department spokesperson James Garrow, as they are the “most common causes of recreational water illness” in the country. Both are spread by swallowing contaminated water and cause diarrhea.

Still, for first-time city visitors walking along the Benjamin Franklin Parkway on a sweltering day, the fountain presents a “magical” opportunity for cooling down.

Among the swimming bunch Tuesday were Hannah Oliver-Willets and her son, Zac Oliver, 5. The duo are originally from Broseley, a small town northwest of Manchester, England. They joined in the water play after they walked by and saw people in the fountain. Despite the sign, she “figured it was the local norm.”

“It’s magical, you know,” said Oliver-Willets, 34.

“It’s so much better to swim in a fountain than in a swimming pool,” she said. “This heat is so hot that all you want to do is put your feet in the water.”

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