Frank Kummer report for Philly.com:

Last week, Joe Ferretti, a Philadelphia Water Department supervisor, pried open a manhole next to a scenic Schuylkill River bank, flicked on a flashlight and peered down.

Ferretti saw evidence sewage was flowing freely into the river at a stone outfall known as S050204.

In some Philadelphia homes, human waste, shower water, dirty dish grease and other stuff that belongs in the sanitary sewer system is going down the wrong pipe, sending it to waterways that feed the Delaware River — the city’s primary source of drinking water.

For years, water department workers like Ferretti have been on a painstaking hunt for “cross connections,” a mild-sounding name that means mixed-up pipes that threaten public health. Between showers, toilet flushes, and sink use, a typical Philadelphia resident uses up to 85 gallons of water a day. That equates to about 272 gallons a day for a typical Philadelphia home – and if there’s a cross connection, that could mean 100,000 gallons going into the river each year.

The stone outfall Ferretti examined — outfall S05204 — is at Kelly Drive in the city’s East Falls section. Water department crews had methodically worked their way up to a block on Ainslie Street, about half a mile from the river, looking for the home, or homes, that were producing the sewage. On a bitterly cold day last week, the crew spent hours outside on their detective work, literally following their noses.