It happens whenever the region gets walloped with those once-in-a-blue-moon deluges that now strike with confounding frequency.
Some of the rains of the last three years have been so great that sewer lines in many parts of the city have become overwhelmed by millions of gallons of runoff, sending wastewater and urban flotsam into basements.
The torrent of rainwater and sewage, sometimes traveling through pipes 25 feet in diameter, has nowhere to go. It flushes into basements via floor drains, utility sinks and toilets - creating a smelly, living-nightmare version of Mickey Mouse's flood during The Sorcerer's Apprentice - without the laughs.
Last June, said Lou Carberry, a longshoreman from Pennsport, sewage backflow shot up from a basement sink "like the fountains on the Parkway."
"We were shin-deep in water with everything you can imagine in there: feces, used condoms, old rags," he said.
"It's a health issue for us," said John Dougherty, president of the Pennsport Civic Association, who also heads the city's Redevelopment Authority. "It's becoming unsafe."
Above ground, Philadelphia is a city on the move, with steel and glass towers reaching higher in the sky and abandoned rowhouses and industrial sites getting new lives as high-end housing.
But below the surface, we're stuck in the 19th century. Many major sewer lines are made of brick, gas pipes of cast iron. Each year, Philadelphia spends millions and millions more to update that infrastructure.
Officials with the Philadelphia Water Department say there's nothing wrong with century-old brick sewer lines; the department spent $1 million in the last year inspecting its underground network for breaks or blockages to be sure.
Instead, the department blames the sewer backups on Mother Nature. Data from the utility show that the city has been hit with an unusual number of fast and furious downpours since the summer of 2004.
"We have a lot of rainfall with nowhere to go," said Joanne Dahme, watershed-programs manager for the Water Department.
Residents in the worst-hit neighborhoods - the Old Kensington section of North Philadelphia, Northern Liberties and Washington Square in the central part of the city, Pennsport and Girard Estates in South Philadelphia - wait with dread as the summer storm season approaches.
A coalition of neighborhood and environmental groups calling itself Next Great City surveyed 800 property owners in the city and found that one in three businesses and one in five residents had had flood problems in the last year.
"It's like Katrina - but underground," said Margaret Kalalian, who belongs to the East Passyunk Crossing Civic Association.
The Philadelphia Water Department knows the city has a problem on its hands - an expensive, complicated problem.
More than 500 customers have filed reports of flooding during the seven heaviest downpours since July 2004.
Dahme said the number of vulnerable properties could be much higher. Based on computer models, sewer backups could affect 1,000 to 5,000 buildings, with the range depending on whether buildings have floor drains or basement sinks or toilets, she said.
She said the sewer system's main trunks were in good shape and downplayed the prevailing suspicion in many neighborhoods that all the new construction in the city was the culprit.
The surge in flood complaints started after a high-velocity storm Aug. 1, 2004, Dahme said.
According to the department's water gauge in South Philadelphia, that storm dumped almost three inches in only an hour - a rate that hadn't been seen in a decade.
Water Department officials thought it was a fluke.
Until it happened again, a month later.
And twice in 2005.
And twice in 2006.
The Water Department will triple the money it spends to replace or augment sewer lines, using $100 million during the next six years for flood relief, Dahme said. It also is thinking about burying a giant underground tank for holding three million gallons of stormwater at Marconi Plaza in South Philadelphia. The tank would be the first of its kind in the city.
More immediately, the Water Department plans to spend as much as $3 million in the year ahead to install special valves in buildings to prevent sewage backflows, Dahme said.
Also, the city is mandating that developers of projects covering more than 15,000 square feet come up with ways to contain the first inch of rainwater - either through retention basins or green space.
Jenifer Fields, head of water management for the Pennsylvania Department of Environmental Protection, said the city was moving forward "in a timely way."
But an official for the Environmental Protection Agency here said she hadn't realized there was much of a problem. "I'm surprised to hear that there are addresses where this is a recurring problem," said Angela McFadden, who oversees enforcement of the Clean Water Act for the EPA's Mid-Atlantic region.
Philadelphia operates 3,000 miles of sewer lines - two-thirds carrying sewage as well as rain runoff. The rest of the system, in parts of the city that were developed later, such as the Far Northeast, has separate lines for sewage and stormwater. In those places, a buildup of stormwater won't mix with sewage.
Dougherty said two South Philadelphia neighborhood groups - his Pennsport Civic Association and the Whitman Council - were prepared to take legal action this summer to force the city to replace the combined lines for sewage and runoff with separate ones.
"We have a better chance of putting in a two-pipe system than controlling global warming," Dougherty said.
In other cities - Washington, Baltimore, Indianapolis, Atlanta, Los Angeles and Louisville, Ky. - the EPA has recently forced major sewer-system improvements because of overflows into waterways.
Dougherty said his basement had flooded three times from sewer backups - even after he installed the valves that the city is recommending as a short-term fix.
"What are we supposed to do, move?" Dougherty said.
Neighbors in Pennsport said they believed that mega-projects - including Citizens Bank Park, Lincoln Financial Field, and the big-box stores along Columbus Boulevard - were contributing to the increase in runoff that burdens the system.
Many noted that the arrival of the Ikea home store in July 2004 - with acres of blacktop for parking - coincided with the start of all the flooding.
Separating raw sewage from rainwater would help protect homes from being invading by tainted water. But Stephen J. Furtek, general manager for planning and engineering for the Water Department, said the cost of converting the sewer system to dual lines would be "insurmountable."
That's little comfort to Dan Rodriguez and his next-door neighbor and cousin, Luis Morales. Their homes sit atop one of the biggest and oldest trunks of the city's sewer system - an 11-foot-wide brick pipe under the 500 block of West Thompson Street in North Philadelphia.
Morales said violent, sudden, hot-weather storms caused all the trouble. The sky turns black; rain falls in sheets; a rivulet builds on the side of the street, growing wider and wider and wider . . .
"Then you see the manhole covers shaking and blowing eight, 10 feet into the air," Morales recalled. "That's when I yell to my cousin, 'Get ready!' "
Floodwaters usually recede quickly, but leave a brown slime in the basement so smelly, the mere memory makes Rodriguez wince. "It's just awful, awful," he said. "If you don't disinfect right away, you could get infections."
Just south of him, in the 100 block of West Allen Street in Northern Liberties, Michael McCandless said he had lost $14,000 worth of belongings - a new heater, a computer, an air-hockey table, power tools, clothes - when his house flooded with four feet of runoff last summer. Insurance covered nothing; the city refused his claim, he said.
His neighbor Marie Frisbie, a single mother of three, is at her breaking point. Six times, she has had to clean up after a noxious brew of sewage and runoff flooded her basement.
"They treat us like we're insane and making this up," Frisbie said. "I'm done. My dream now is to live in a condo, on the third floor so I'll never have to deal with flooding ever again."
Whom to Call if Your Basement Floods
To report flooding, call the Philadelphia Water Department at 215-685-6300.
To answer the Water Department's flooding questionnaire, go to www.phila.gov/water/pr/2006_flood_Q.htm
To report complaints to the Environmental Protection Agency, go to www.epa.gov/compliance/complaints/index.html
To see video and hear the flood stories of six Philadelphia homeowners, go to
Contact staff writer Jennifer Lin
at 215-854-5659 or email@example.com.