Residents are not allowed to tap into fire hydrants to turn dumpsters into swimming pools.

"We are not screwing around, Philly," the department wrote, listing several reasons why "you shouldn't swim in a receptacle most often used for waste."

City officials made that declaration after a block party last weekend in Kensington became an online sensation after residents power-washed a dumpster and lined it with plywood and tarps and filled it with water from a nearby hydrant. That incident was first reported by online news outlet Billy Penn.

Karen Guss, spokeswoman for L&I, said the aggressive response was due to the city's attention to public health, safety, "and basic common sense."

"We will not issue permits for block party dumpster pools," Guss wrote. "And while you would think this decision would not require an explanation, three days of press requests have proven otherwise."

The top concern revolved around the city's fire hydrants.

Illegally tapping those hydrants would deplete the reserves needed in case of a fire, Guss said. She also said the high-pressure release of water could injure or kill people in its path, cause water-main breaks, and add other costs to the city.

Mike Dunn, a city spokesman, said that the Kensington group did not obtain a permit, as required, to put a dumpster on the street.

He also expressed concern about draining 24,000 pounds of water into the street, potentially causing flooding, property damage, or sewer overload.

"The city strongly recommends that residents opt for recreational options that are safer, more sanitary, and less likely to deplete the resources firefighters need in an emergency," Guss said. "You would think this decision would not require an explanation."

[Updated: An earlier version of this post gave the wrong neighborhood for the original pool.]